FOR THE PEOPLE FOR EDVCATION FOR SCIENCE LIBRARY OF THE AMERICAN MUSEUM OF NATURAL HISTORY ! CD nj o m CD THE ANATOMY OF VERTEBRATES, VOL. III. LONDON: PRINTED BY SPOTTISWOODE AND CO., NEW-STBEET SQUARE AND PARLIAMENT STREET ON THE -A. ^ ANATOMY OF VERTEBRATES. VOL. III. MAMMAL S. BY RICHAED OWEN, F.R.S. SUPERINTENDENT OP THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM, FOREIGN ASSOCIATE OP THE INSTITUTE OF FRANCE, ETC. LONDON : LONGMANS, GREEN, AND CO. 1868. A c lc CONTENTS, OR SYSTEMATIC INDEX. -OH CHAPTER XXVII. MUSCULAR SYSTEM OF MAMMALIA. SECTION PAGE 192. Diaphragm .......... . 1 193. Muscles of Monotremata 2 194. Muscles of Marsupialia ........ 8 195. Muscles of Lissencephala ......... 16 196. Muscles of Cetacea . 24 197. Muscles of Perissodactyla ......... 26 198. Muscles of Artiodactyla ... ..... 41 199. Muscles of Carnivora ......... 49 200. Muscles of Quadrumana ....... . 52 201. Muscles of Bimana .......... 54 202. Locomotion of Mammals . ....... 63 A. Swimming ........... 65 B. Moving on Land ... .... .66 CHAPTER XXVIII. NERVOUS SYSTEM OF MAMMALIA. 203. Myelon . . .73 204. Encephalon, its primary divisions 79 205. Macromyelon .... . .... 81 206. Cerebellum 88 207. Mesencephalon ...... .... 97 208. Prosencephalon ........... 99 A. Lyencephala . .... ..... 100 S. Lissencephala ... ......108 C. G-yrencephala . . . . . . . . . . 114 D. Archencephala . . . . . . . . . . 127 209. Size of Brain 143 210. Membranes of Brain . . . 145 VI CONTENTS. SECTION 211. Nerves of Mammals 212. Sympathetic System 213. Organs of Touch .... 214. Organ of Taste .... 215. Organ of Smell .... 216. Organ of Hearing 217. Organ of Sight .... A. Eye-ball .... B. Appendages .... C. Parallel between Eve and Ear PAGE 146 181 186 190 204 219 246 246 258 263 CHAPTER XXIX. DENTAL SYSTEM OF MAMMALIA. 218. General Characters of the Teeth .... 219. Teeth of Monophyodonts A. Monotremata ..... T5. Bruta .... C. Cetacea ..... 220. Teeth of (non-ungulate) Diphyodonts . A. Sirenia .... B. Marsupialia ...... C. Rodentia ........ D. Insectivora ........ E. Quadrumana . ....... F. Bimana Gr. Carnivora ........ 221. Teeth of Ungulate Diphyodonts A. Homologies of the Grinding Surface of Molars B. Artiodactyla ........ C. Perissodactyla ... ... D. Proboscidia ...... 222. Homologies of Teeth 265 271 271 272 276 283 283 285 294 301 313 322 327 340 340 343 352 359 366 CHAPTER XXX. ALIMENTARY CANAL AND APPENDAGES OF MAMMALIA. 223. Mouth . . . 224. Salivary Glands .... 225. Alimentary Canal of Lyencephala . 226. Alimentary Canal of Rodentia 227. Alimentary Canal of Insectivora . 228. Alimentary Canal of Cheiroptera . 229. Alimentary Canal of Quadrumana 230. Alimentary Canal of Bimana 231. Alimentary Canal of Carnivora 383 396 410 420 427 428 429 434 442 CONTENTS. Vll SECTION PAGE 232. Alimentary Canal of Bruta 446 233. Alimentary Canal of Cetacea ........ 452 234. Alimentary Canal of Sirenia ......... 454 235. Alimentary Canal of Proboscidia 457 236. Alimentary Canal of Perissodactyla 458 237. Alimentary Canal of Artiodactyla 465 238. Liver of Mammals .......... 478 239. Pancreas of Mammals .......... 492 240. Peritoneum and Appendages of Mammals ...... 500 CHAPTER XXXI. ABSORBENT SYSTEM OF MAMMALIA. 241. Lacteals ............ 504 242. Lymphatics ............ 506 243. Absorbent ganglions .......... 508 244. Disposition of Lymphatics ......... 508 245. Mammalian modifications . . ..... 511 CHAPTER XXXII. CIRCULATING SYSTEM OF MAMMALIA. 246. Blood of Mammals ......... 513 247. Heart of Mammals .......... 516 A. Lyencephala . . . . . . . . . . . 516 B. Lissencephala . . . . . . . . . . 519 C. Cetacea ........... 520 D. Sirenia 521 E. Ungulata ........... 522 F. Carnivora ........... 523 Gr. Quadrumana ........... 525 H. Bimana 525 248. Arteries of Mammals ... 532 249. Veins of Mammals 549 250. Spleen of Mammals .......... 557 251. Thyroid of Mammals . 563 252. Thymus of Mammals 566 253. Adrenals of Mammals . 568 CHAPTER XXXIII. RESPIRATORY SYSTEM OF MAMMALIA. 254. Lungs of Mammals ... . 572 255. Larynx of Mammals ........ . 582 VI 11 CONTENTS. CHAPTER XXXIV. URINARY SYSTEM OF MAMMALIA. SECTION 256. A. Kidneys .... B. Urinary Bladder and Urethra . PAGE 604 609 CHAPTER XXXV. TEGUMENTARY SYSTEM AND APPENDAGES OF MAMMALIA. 257. Derm 610 258. Epiderm and ' rete mucosum ' 613 259. Callosities 616 260. Hair 616 261. Spines ............. 621 262. Scales 622 263. Nails, Claws, and Hoofs . 623 264. Horns ...... .... 624 CHAPTER XXXVI. PECULIAR GLANDS OF MAMMALIA 265. Opening npon the Head 266. Opening upon the Trunk 267. Opening upon the Tail . 268. Opening upon the Limbs 632 634 637 638 CHAPTER XXXVII. GENERATIVE ORGANS OF MAMMALIA. A. Male Organs 269. In Monotremata 270. In Marsupialia 271. In Rodentia 272. In Insectivora 273. In Bruta 274. In Cetacea 275. In Sirenia 276. In Proboscidia 277. In Perissodactyla 278. In Artiodactyla 279. In Carnivora 641 643 645 649 655 657 658 660 660 661 666 668 CONTENTS. IX SECTION 280. In Quadrumana . 281. In Bimana . B. Female Organs 282. In Monotremata . 283. In Marsupial! a 284. In Rodentia 285. In Insectivora 286. In Bruta 287. In Cetacea . 288. In Sirenia . 289. In Proboscidia 290. In Perissodactyla 291. In Artiodactyla . 292. In Carnivora 293. In Quadrumana . 294. In Bimana PAGE 672 673 676 677 680 686 687 689 691 692 692 693 694 698 701 704 CHAPTER XXXVIII. GENERATIVE PRODUCTS AND DEVELOPMENT OF MAMMALIA. 295. Ovulation .... 709 296. Ovipont 711 297. Corpus Luteum 712 298. Impregnation ........... 713 299. Development of Monotremata . . . . . . . . 715 300. Development of Marsupialia ........ 718 3J1. Development of Lissencephala. ........ 723 302. Development of Mutilata 732 303. Development of Ungulata ......... 732 304. Development of Carnivora ......... 742 305. Development of Quadrumana ........ 745 306. Development of Bimana ......... 747 307. Development of Mammalian brain . . . . . . . 751 308. Development of Mammalian skeleton ....... 753 309. Membrana pupillaris ......... 754 310. Foetal Circulation .......... 755 311. Definition of Male and Female Organs 757 312. Descent of Testes. . 758 CHAPTER XXXIX. MAMMARY AND MARSUPIAL ORGANS. 313. In Monotremata 314. In Marsupialia 315. In Lissencephala 316. In Mutilata 317. In Ungulata 760 768 775 777 778 X CONTENTS. SECTION TAGS 318. In Garni vora ........... 780 319. In Qiiadrumana ........... 780 320. In Bimana ....... ... 781 321. Adipose Substances .......... 783 CHAPTER XL. GENERAL CONCLUSIONS. 322. Biological Questions of 1830 786 323. Horaology or Teleology ? 787 324. Succession of Species, broken or linked ?...... 789 325. Extinction of ditto, cataclysmal or regulated? ..... 797 326. How works the Derivative Law? 799 327. Epigenesis or Evolution ? ......... 809 328. Nomogeny or Thaumatogeny ? 814 WORKS REFERRED TO .......... 827 ZOOLOGICAL INDEX . . . . . . . . . . 839 GENERAL INDEX . ........ 859 EEEATA. Page 26, four lines from bottom, premise f 197. Muscles of Perissodactyla.' ,, ,, thirteen lines from bottom, for ' (sterno-humeralis),' read ' (cephalo-huineraht;.' 49, note l for ' vi.,' read ' vi".' 72, note 3 for ' cxxxi'.,' read ' cxxxi.' 81 , note 5 for ' I/'. ,' read ' xxiv".' ,, 100, sixteen lines from top, premise ' A. Lyencephala.' 120, fig. 95, for ' xxxix".,' read ' xxix".' 129, note ' for ' ix'.,' read ' rx" '. ,, 144, note * for ' LVHI'.,' read ' LYin".' ,, 206, to description of fig. 152, add ' Human.' 212, note * for ' xcm.,' read ' xcra".' 251, note 1 for ' cv".,' read ' cix".' 255, below cut 20, for v".,' read ' cv".' 266, note * for ' xxv".,' read ' xxxix".' ,, 368, last line, for ' first true molar,' read ' first lower true molar.' ,, 412, note J for ' cxxn".,' read ' cxxn'.' 424, note 1 for ' cxxn"., xxm.,' read ' cxxn'. vol. xiii.' ,, 427, five lines from top, for ' 327,' read ' 227 ; ' and so on to ' 399, p. 715,' for which read ' 299.' 428, ten lines from top,/or ' fig. 359,' read fig. 389." 450, ' fig. 354,' for ' cxxn'.,' read ' CXXIi".' 460, note J for ' cxxi.,' read ' cxxn'.' 473, note l for ' ccxxn".,' read ' cxxn'. 479, note 2 for ' cxn".,' read ' cxxn'.' ,, 515, note B for ' Ib.,' read ' CLXXIX".' 535, note "for ' xcvrn".,' read ' xcvn'.' 536, note * for ' cxcii",' read ' xxxiv".' 542, note ' for ' cxLm".,' read ' cxxxi".' 536, note 4 for ' cxcn".,' read ' xxxiv".' 622, twelve lines from top, for fig. 489,' read 4 fig. 489, i.' 637, fourteen lines from bottom, for ' glossa,' read ' fossa.' 718, for ' 400,' read ' 300 ; ' and so on to ' 428, p. 813,' for which read ' 328.' ,, 790, nineteen lines from top,/o/- ' Palceotheria,' read ' Spalacotheria.' THE ANATOMY OF VERTEBRATES. CHAPTER XXVII. MUSCULAR SYSTEM OF MAMMALIA. THE muscular tissue in the present as in the preceding Vertebrate classes presents the two conditions of striped and unstriped elemen- tary fibres : the striped kind, comprising all the voluntary muscles with those of the heart, are red : deeper coloured in Cetacea and Carnivora than in Uncjulata : deeper in the pectoral muscles of Cheiroptera than in those of the legs : paler in the pectorals and other muscles of the fore-legs of the Kangaroo than in the ' psoae ' and those of the hind-legs : palest in some Rodentia. 1 92. The Diaphragm.- -The chief characteristic of mammalian myology is the diaphragm, vol. ii., fig. 139, d, which, as such, is not more completely developed in Man than in the Monotreme. It is the partition between the thoracic and abdominal cavities, fig. 1, vaulted and convex toward the thorax, fig. 2, and consists of carneous and tendinous parts, the latter chiefly In the expanded or aponeuro- tic form. The carneous fas- ciculi are divided into the ( costal ' or greater and the ( vertebral ' or smaller mus- cles. The costal portions arise from the ensiform cartilage, and those of the eighth to the twelfth ribs, by fasciculi which inter- digitate with those of the 6 transversalis abdominis ' mUSCle. I hey aSCeild and Human diaphragm ; abdominal surface. expand, arching and con- to be inserted into the external ( ligamentum arcuatum,' B VOL. Til. 2 ANATOMY OF VERTEBRATES. fig. 1, d, and into the aponeurosis called f centrum tcndineum' or 'cordiform tendon,' ib., T. This centre is widely notched toward the spine, and divided anteriorly into three tracts, of which the right is usually the largest. Between the right and middle tracts is the orifice, c, for the inferior vena cava (' postcaval ' of Mam- mals). Behind the tendon, and to the left of the median line, is the orifice, e } for the oesophagus and pneumogastric nerves : the aorta, , passes from the chest to the abdomen be- tween the f crura ' of the "lesser muscle. The right 6 crus ' in Man arises from the three or four upper lum- bar vertebras ; the left crus does not descend so low : both muscular bundles ex- pand as they rise, decus- sate at the ossophageal open- ing, and are inserted into the posterior concavity of the central tendon and in- ternal ligamentum arcua- tum, fig. I,/. The diaphragm is most muscular, longest, and most oblique in Cetacea, in which the central tendon is almost obsolete : by rising so far back, it permits the proportional extension of the lungs, which in the Duo-ono; and Manatee act as air-bladders. In the o ~ perissodactyle Ungulates, in which the moveable ribs are numerous and continued to near the pelvis, the diaphragm is also extensive, and much arched toward the thorax. 193. Muscles of Monotremata. To give an account of the muscular, as fully as that of the osseous, system of the Mammalia, would not be attended with the same advantages, even if a detailed myology comported with the scope and extent of the present work. This part of Mammalian anatomy will therefore be limited to the notice of a few select examples. Fig. 3, from Meckel, 1 shows the more remarkable muscles of the Ornithorhynchus. The animal is dissected from the ventral surface ; the great e panniculus carnosus,' i, is reflected from the right side, and the deeper-seated muscles are shown on the left. The panniculus carnosus, which is remark- able for its thickness, encompasses nearly the whole body, adhering most firmly to the external skin, but separated from the subjacent muscles, especially where it covers the thorax, abdomen, the arm, 1 LXXI-. Human diaphragm. Thoracic surface from behind. MUSCULAR SYSTEM OF MAMMALIA. 3 and the thigh, by a copious and lax cellular tissue ; and in the female, at the abdominal region, by the mammary glands. The fibres are chiefly longitudinal, but at the lower part of the neck become transverse. The obtuse posterior end of the muscle is at- tached by three or four fasciculi to the dorsal aspect of the caudal diapophyses. The legs and the arms protrude through oblique apertures in this muscular tunic ; some of the anterior fasciculi are inserted by a short tendon into the pectoral ridge of the humerus ; and others, still more anterior, are attached to the cranium, the lower jaw, and lower lip. A strip of fibres, which is cut off at i*, is attached to the os hyoides ; another fasciculus (V) spreads over the cheek-pouch, r, and assists in emptying that receptacle of the food. The trapezius, 9, is divided into two muscles ; the posterior por- tion is an oblong slender triangle arising by a broad tendon from the tenth and eleventh vertebrae and ribs, and inserted by a short strong tendon behind the extremity of the spine of the scapula ; the anterior portion arises from the occiput and tendinous raphe con- necting it with its fellow of the opposite side, and is inserted into the spine of the scapula, and into the outer half of the clavicle. The latissimus dorsi, a very long and broad muscle, arises from the spines of all the dorsal and lumbar vertebrae and from the eleven posterior ribs ; it is inserted by a broad and strong tendon into the distal half of the ulnar margin of the humerus, and, with part of the ( panniculus,' into the fascia attached to the olecranon and spreading over the fore-arm. At its anterior part this muscle may be separated into a superficial and deep stratum. The r/wm- boideus is a single muscle, but thick and long, inserted into the narrow base of the scapula. The splenius capitis is united by an intermediate tendon with the opposite muscle, and is inserted into the mastoid process. The biventer cervicis and the complexus are distinct throughout their whole course, which extends from the anterior dorsal and posterior cervical spines to the occiput ; the complexus is the longest and thickest muscle, and divides into an external, shorter, and deeper-seated portion, and an internal, longer and superficial portion. The sacrolumbalis arises from the dorsal extremity of the ilium, is attached to the ribs, over which it passes in its course to its insertion into the transverse processes of the four or five posterior cervical vertebrae : it is continued by the f cervicalis ascendens ' to the atlas. The longissimus dorsi is a much thicker and narrower muscle, B 2 .Muscular system, ventral aspect. Ornithorhynclms paradoaxts, LXXXV MUSCULAR SYSTEM OF MAMMALIA. 5 and extends from the dorsal aspect of the sacrum along the spine to the third or fourth cervical vertebra. It is continued forward by the transversalis cervicis and trachelo-mastoideuSywhicln. are blended into a sino-le oblono; muscle arising; from the anterior dorsal and o o inserted into the transverse processes of the six lower cervical vertebra? and the mastoid process. The sterno-mastoid is a double muscle on both sides, one por- tion being superficial, 8, the other deep-seated ; each arises sepa- rately from the episternum, and is separately inserted into the mastoid. The omo-hyoideus, 10, and mylo-luj 'oideics, 10, have a common insertion into the hyoid. A muscle, i" ', arising from the basi-hyal and expanding to be inserted into the lower lip, serves to retract this part. The sterno-hyoideus, u, joins the liyo- ylossus. The genio-hyoideus, 12, and the stylo -hyoideus, is, have the normal relations : the biventer maxilla, H, is a short thick muscle, inserted near the bend, representing the angle, of the jaw. The caudal muscles are powerfully developed. The oblique fibres of the inferior or deflector muscles are shown at 63 ; they are removed on the other side to expose the anterior caudal nerves, z. The obliquus externus abdominis, 3, 3, arises from all the vertebral ribs, except the first, and from the dilated ex- tremity of the ilium ; it is inserted by a strong tendon into the outer extremity of the marsupial bone, VI, then expands into an aponeurosis which is attached to the internal margin and base of that bone, and into the symphysis pubis, decussating with the tendinous fibres of the opposite muscle : it does not split to form an ( abdominal ring.' The olliquus interims, 6, arises from the anterior part of the ilium, expands, and is inserted into the broad cartilages of the seven posterior ribs, v, v. The transversus abdominis, 7, is a thicker muscle, and arises from both the ilium and the lumbar diapophyses ; its tendon passes behind the recti to blend with that of the opposite muscle, and with the aponeurosis of the obliqui externi, in the linea alba. The pyramidalis, or superficial rectus, 4, is here, as in the ordinary Marsupials, of very large size ; it arises from the whole inner margin of the marsupial bone ; its fibres converge toward and are confluent at the linea alba with those of its fellow, and it gradually terminates in a point opposite the posterior part of the sternum. It depresses the ribs, shortens the abdomen, and pro- tracts the marsupial bone. The rectus abdominis, or posterior rectus, 5, arises from the posterior margin of the marsupial bone, and is inserted into the 6 ANATOMY OF VERTEBRATES. cartilage of the first rib, the manubrium sterni, and the coracoid bone. The diaphragm presents the structure which is characteristic of the true mammiferous animal. The lesser muscle arises from the first lumbar and four last dorsal vertebrae, and expands to be inserted into the central tendon, which chiefly receives the fibres of the greater muscle arising from the cartilages of the eleven inferior pairs of ribs. The pectoralis, 2, is of very striking dimensions ; the origin of the superficial portion extends from the acromion and episternum, along the sternum and linea alba, almost to the pubis ; a deeper- seated portion arises from the six osseous sternal ribs ; the fibres of both portions converge to be inserted into the largely-developed pectoral or anterior crest of the proximal half of the humerus. The pectoralis minor is attached to the coracoid, and the sub- clavius is likewise inserted, as in some other quadrupeds, into this bone, which is no longer a subordinate process of the scapula in the Monotremes. The subscapularis is a narrow muscle, and narrower in reality than at first sight it appears to be, since the supraspinatus, from the inflection of the spine and acromion, arises from the same aspect of the scapula, and appears to form the anterior fasciculus of the sub scapular is ; its distinct insertion into the anterior tubercle of the head of the humerus points out its true nature. The infraspinatus, 20, and the large teres major cover the whole external surface of the scapula. The deltoid is divided into an anterior and a posterior portion. The anterior portion, 19, arises from the anterior extremity of the coracoid, and is inserted into the summit of the deltoid crest of the humerus: the posterior part, 21, arises from the anterior and superior apex of the scapula, and is inserted into the lower half of the deltoid crest. There are also two muscles to which the name coraco-brachialis may be applied, a superior one, 22, and an in- ferior one, 25. The biceps brachii arises by two heads ; one, 23, arises from the sternal extremity of the coracoid, the other, 24, also arises from the coracoid ; the common tendon is inserted into the middle of the radius. The other muscles of the anterior extremity adhere closely to the Mammalian type. The extensor carpi radialis, so, sends three tendons, to be inserted respectively into the second, third, and fourth metacarpal bones. There is a single common flexor diai- torum, as well as extensor diaitorum, 27. The extensor diaiti minimi, 26, the indicator, 28, the extensor MUSCULAR SYSTEM OF MAMMALIA. 7 pollicis, 29, the pronator teres, 32, and the flexor carpi radialis, 33, are all remarkable for their strength in the Ornithorhynchus, and are still more powerfully developed in the Echidna. The most remarkable muscle on the palmar aspect of the fore arm is the flexor carpi ulnaris, which arises by two separate heads, the longer one from the broad olecranon, the shorter one from the internal condyle of the humerus ; the common tendon is attached to the os pisiforme and the rnetacarpals of the fourth and fifth digits. The psoas magna and iliacus interims form a single muscle, having the usual origins, and inserted by a common tendon into the large internal trochanter. The psoas minor is the largest of these muscles. It arises from the sides of five dorsal vertebras, and its strong tendon is implanted in the remarkably developed ilio-pectineal process. It depresses the pelvis, and with it also the tail and the pelvic extremities. The ectoyluteus is larger than is usually the case with qua- drupeds ; its insertion extends to the plantar fascia and the bone which supports the spur. The mesogluteus, entogluteus, pectineus, 45, biceps flexor cruris, gracilis, 34, sartorius, 35, rectus femoris, 36, adductores femoris, 46, semitendinosus, 47, semi-mem- branosus, vastus externus, offer no notable deviations from the usual structure. A strip of fibres, 49, descends from the gracilis to the sphincter cloacce, H. A muscle, called by Meckel ( flexor accessorius a cauda ad tibiam tendens,' 51, arises from the trans- verse processes of the anterior caudal vertebrae, and converges to be inserted into the tibia. Another peculiar adductor of the leg, which might be termed ( intertibialis,' 52, is attached by its ex- tremities to both tibiaa ; its fleshy belly passes across the sphincter cloacaa, H, and is connected with a strip of the panniculus car- nosus, i. The gastrocnemius, 48, derives its largest origin from the pro- duced and expanded head of the fibula, and its smaller belly from the internal femoral condyle ; its tendon is implanted in the cal- caneum. The homotopy between the gastrocnemius and flexor carpi ulnaris is strikingly illustrated in the Ornithorhynchus. The soleus arises from the head of the fibula and from a large pro- portion of the tibia ; it is nowhere blended with the gastrocnemius, but is inserted by a thick and short tendon into the astragalus. The abductors of the outer digits of both the hand and foot are well developed for the purpose of expanding the web which connects the toes. In the fig-ure the following muscles of the les; are shown viz. o o o 37, tibialis anticus, 38, extensor hallucis longus, 39, peroneus longus, 8 ANATOMY OF VERTEBRATES. 40, peroneus brevis, 4i, extensor digitorum profundus, 42, extensor digitorum xiihlunis, 43, a portion of the same muscle corresponding with the indicator of the fore leg, and 44, extensor diyiti quinti accessorius. 194. Muscles of Marsupialia.- -The most common posture of the Kangaroo is often termed the ' erect ; ' yet the conditions of this posture are very different from those in the human subject. The trunk, instead of resting upright on two nearly vertical pillars, is here swung upon the femora as upon two springs, which descend from the knee-joints obliquely backward to their points of attachment at the pelvis ; and the trunk is propped up behind by the long and powerful tail, vol. ii., fig. 211. In Man the massive and expanded muscles which find their attachment in the broad bones of the pelvis, especially at the posterior part, are the chief powers in maintaining the erect posture. But in the Kangaroo the ylutcei offer no corresponding predominance of size ; the narrow prismatic ilia could not, in fact, afford them the requisite extent of fixed attachment. The chief modifications of the muscular system in relation to the erect position of the trunk in the Kangaroo are met with on the anterior part of the base of the spinal column. The psocz parvcB, for example, present proportions the reverse of those that suggested their name in human anatomy. They form two thick, long, rounded masses, which take their origin, fleshy, from the sides of the bodies and base of the diapophyses of the lower dorsal and all the six lumbar vertebra?, and from the extremities of the three last ribs ; the fibres converge pemiiformwise to a strong, round, middle tendon, inserted in the well-marked tubercle or spine of the pubis, already noticed. The abdominal muscles include a pyramidalis as remarkably developed as in the Monotremes. In the Phalanger, fig. 4, the external oblique., besides the usual origin by digitations from the ribs, also arises from the fascia luiiiborum ; it is in- serted fleshy into the summit of the marsupial bone, a, over which its strong inner tendon is spread : the external oblique becomes aponeurotic at a line continued from the marsupial bone outward, with a gentle curve, toward the anterior ex- tremity of the ilium ; and in the opposite direction, or inward, the carneous fibres of the external oblique terminate in an apoueurosis along a line parallel with the oblique outer margin of the pyramidalis ; the fascia continued from the latter boundary of the fleshy fibres passes over, or dermad of, that muscle, and meets its fellow at the linea alba ; it is homologous MUSCULAR SYSTEM OF MAMMALIA. ing Abdominal muscles, 1'iitilauijinta rulpina. with the anterior layer of the sheath of the rectus in ordi- nary Mammalia. It is seen reflected from the pyramidalis, at by fig. 4. The aponeurosis continued from the external and inferior boundary of the carneous fibres divides as usual into two distinct por- tions. One, a, correspond- to the internal or mesial pillar of the abdo- minal ring, spreads its glistening fibres, as above described, over the dermal surface of the marsupial bone, c, to which it closely adheres : the other co- lumn, d, contracts as it descends obliquely in- ward, forms, like ' Pou- part's ligament,' the upper boundary of the space through which the psoas and iliacus muscles and femoral vessels and nerves escape from the pelvis, and is finally inserted, thick and strong, into the outer end of the base of the marsupial bone. This bone is so connected with the pubis that its movements are almost limited to directions forward and backward, or those concerned with the dilatation and diminution of the abdominal space ; the contraction of the abdominal muscles must draw the bones inward so as to compress the contents of the abdomen, and so far as the connections of the bone permit, which is to a very trifling degree, the external oblique may draw it outward toward the ilium. In some Marsupials, as the Koala, the triceps adduc- tor femoris sends a slip of fibres to the external angle of the base of the marsupial bone, and would more directly tend to bend that bone outward. The upper or anterior fibres of the internal oblique have the usual origin ; the lower ones, e, arise fleshy from the outer and anterior spine of the ilium, and for an inch along an aponeurotic chord extended from that process to the upper part of the aceta- bulum : these carneous fibres pass inward and slightly upward, and terminate close to the outer margin of the rectus, where they adhere very strongly to the transversalis, but give off a separate sheet of thin aponeurosis which is lost in the cellular sheath of the posterior rectus. 10 ANATOMY OF VERTEBRATES. The fleshy fibres of the transversalis abdominis, f, are closely connected by dense cellular tissue with those of the internal oblique ; they are arranged in finer fasciculi, and have, as usual, a more transverse direction ; they terminate along the same line as those of the internal oblique in an aponeurosis, g, which is continued along the inner or central surface of the posterior rectus to the median line. The lower boundary of the fleshy fibres of the transversalis is parallel with the line extended transversely between the anterior extremities of the ilia ; a fascia, less compact than an aponeurosis, is continued downward from this margin, and envelopes the cremaster and the constituents of the spermatic chord, as they pass outward and forward beneath the lower edge of the internal oblique. The pyramidalis, h, arises from the whole inner or mesial margin of the marsupial bone, from which the fibres diverge, the lower ones passing transversely across the interspace of the bones, and meeting at a very fine raphe, or linea alba ; while those fibres from the anterior ends of the marsupial bones gradually exchange their transverse direction for one obliquely forward. The breadth of each pyramidalis opposite the upper end of the marsupial bone is more than an inch, the thickness of the muscle one line. The rectus abdominis, i, comes off from the pubis along the inner part of the strong ligamentous union of the broad base of the marsupial bone, and expands as it ascends until it attains the level of the ensiform cartilage, when it diminishes as it is inserted into the sternal extremities of the ribs reaching to the manubrium sterni and first rib in the Dasyures, as in the placental Carnivores. The slight indications of tendinous intersections are confined to the posterior or central superficies of the muscle. The cremaster , k, in the Phalanger and Opossum, is not a fasciculus of fibres simply detached from the lower margin of the internal oblique or transversalis, but arises by a narrow though strong aponeurosis from the ilium, within and a little above the lower boundary of the internal oblique, with the fibres of which the course of the cremaster is not parallel ; it might be considered as a part of the transversalis, but it is separated by the fascia above mentioned from the carneous part of that muscle. Having emerged from beneath the margin of the internal oblique, the cremaster escapes by the large elliptic abdominal ring, /, bends round the marsupial bone near its free extremity, and expands upon the tunica vaginalis testis. In the female it has the same origin, course, and size, but spreads over the mammary glands at MUSCULAR SYSTEM OF MAMMALIA. 11 the back of the pouch. If the anterior fascicles of the div and embracing fibres be dissected from the posterior ones, the appearance of the cremaster dividing into two layers is produced. The principal modifications of the muscles of the pectoral ex- tremity are here described as they exist in the Perameles lagotis. The trapezius has its origin extended from the skull, along the cervical and dorsal spines, to the fascia covering the lumbar por- tion of the latissimus dorsi : its fibres converge to be inserted alono- . the spine of the scapula, the anterior ones being directly continued into the pectoralis major, whereby it becomes an extensor of the humerus and a protractor of the fore extremity. The latissimus dorsi arises chiefly from the broad aponeurosis covering the muscles of the lumbar region of the spine, and from the spines of the six posterior dorsal vertebras ; the fibres gradually converge, the muscle increasing in thickness as it diminishes in breadth, and terminating in a strong flattened tendon one inch before its insertion at the upper third of the humerus. It is con- nected, as in most brutes, up to and including the Gorilla, with an accessory extensor (pmo-anconeus) * of the antibrachium. This ex- tensor takes its principal origin by fleshy fibres from the terminal half inch of the fleshy part of the latissimus dorsi, and continues fleshy, slightly diminishing in size to its insertion at the apex of the olecranon. To remedy the inconvenience of an origin from a yielding and flexible part, a thin aponeurotic slip, in Peramelcs, attaches a part of the base of the superadded muscle and the cor- responding portion of the latissimus dorsi to the sheath of the teres major, and to the inferior costa of the scapula near its posterior angle. The supraspinatus, a strong penniform muscle, exceeds the infraspinatus in breadth by as much as the supra-spinal fossa is broader than the infra-spinal one : it has a broad and strong insertion into the great outer tuberosity of the humerus. The infraspinatus is inserted into the upper and posterior part of that tuberosity. The deltoides is a comparatively small muscle ; it arises from the anterior half of the spine of the scapula and from a fine aponeurosis covering the infraspinatus ; its fibres converge to be inserted in the upper part of the deltoid ridge. A thin small strip of muscle arises from about the middle of the inferior costa of the scapula, beneath the infraspinatus ; its fibres pass forward and join the lower margin of the small del- toid, thus bracing and enclosing the tendon of the infraspinatus. p. 289 (1846): the muscle is termed ' dorso-epitrochlien' by Duvernoy in the Gorilla, i". p. 80 (1855), where it is inserted into the inner condyle of the humerus. 12 ANATOMY OF VERTEBRATES. In claviculate marsupials the deltoid is larger, and consists of three fasciculi. The teres major is a strong sub-compressed muscle arising from near the posterior half of the inferior costa of the scapula, and joining, as before stated, the tendon of the latissimus. The triceps extensor has its long portion arising from the anterior third of the inferior costa of the scapula ; its second head comes from the posterior part of the proximal third of the humerus ; the third portion takes its origin from the whole of the posterior part of the humerus ; in addition to these, the olecranon receives the above-described fourth superadded slip from the latissimus dorsi. The pectoralis major is, as usual in the Marsupial and many higher quadrupeds, a complicated muscle ; it consists of an anterior or superficial and a posterior or deeper portion ; the anterior portion receives the strip of fibres before mentioned from the trapezius, there being no clavicle or clavicular ossicle interposed in the Pe- rameles ; its fibres converge, increasing in thickness as they diminish in breadth, and are inserted into the anterior and outer part of the strongly developed pectoral ridge. The second and main portion of the pectoralis arises from the whole extent of the sternum ; its fibres are twisted obliquely across each other as they converge to be inserted into the inner part of the pectoral ridge ; some of the internal and posterior fibres of this portion of the twisted pectoral pass obliquely upward and behind the anterior fasciculi, and are inserted into the coracoid process, thus repre- senting the pectoralis minor. Beneath this latter portion of the pectoral, a long and slender muscle passes to be inserted into the anterior part of the tuberosity of the humerus ; this may likewise be regarded as a dismemberment of the pectoralis major, but it arises from the fascia of the rectus abdominis, below the car- tilages of the lower ribs. Thus the strong pectoral ridge of the humerus is acted upon by muscles having a range of origin from the occiput and cervical vertebra? along the whole extent of the chest to the beginning of the abdomen. The biceps is a powerful muscle, although its short head from the coracoid process is suppressed. The long head has the usual origin and relation to the shoulder-joint ; its tendon is very thick and short. The fleshy belly joins that of the strong brachialis in- ternus, situated at the external side of the humerus, whence it takes its principal origin from the short deltoid ridge, closely con- nected there with the second portion of the triceps, and deriving some fleshy fibres from the lower and outer third of the humerus. The portion of the biceps arising by the long head soon resolves MUSCULAR SYSTEM OF MAMMALIA. 13 itself into two distinct pemiiform muscles ; the tendon of the outer one joins that of the brachialis, and this conjoined tendon simply bends the fore-arm, while the inner tendon bends and pro- nates ; the latter, which is a direct though partial continuation of the biceps, is inserted into the ordinary tubercle of the radius ; whereas the outer tendon is attached to the fore part of the proxi- mal end of the ulna. The muscles which arise from the internal condyle of the humerus are the pronator teres, which has the usual origin, insertion, and relative proportions, and next a large pal- inaris longus. There are, likewise distinct and strong fasciculi of muscles corresponding to tia&Jlexores carpi ulnaris and radialis, and to thejferor sublimis diyitorum. The strong ridge continued from the olecranon to the posterior and inner part of the ulna gives origin to a great proportion of the oblique fibres of the flexor pro- fundus ; but both this and thejflexor sublimis terminate in a single thick and strong tendon, which after passing the wrist divides into those corresponding with the perforating and perforated tendons concentrated, in Perameles, upon the three long middle fingers. The pronator quadratics runs the whole length of the interosseous space, passing from the radius a little obliquely downward to the ulna. The supinator longus, arising as usual from the upper part of the strongly developed ridge above the outer condyle, sends its tendon across the carpal joint, which tendon divides before it crosses, and is inserted by one of its divisions into the base of one of the metacarpal bones of the index finger, and by the other into the adjoining metacarpal bone. These are the principal muscles of the fore extremity which require notice. Their modifications, in respect of number and strength, relate to the act of digging up the soil, which is habitual in the Bandicoots, as it is for the purpose of obtaining food, and not for shelter. It is for this purpose that the three middle digits of the hand are developed at the expense of the other two, which are rudimental ; the whole power of the deep and superficial flexors is concentrated upon the fossorial and well-armed fingers ; and, by the sinoie common tendon in which the fleshy fibres of j ~ > these muscles terminate, they move them collectively and simul- taneously. Thus variety of application, and especially the pre- hensile faculty, are sacrificed to the acquisition of force for the essential action. In no Marsupial is the hand so cramped as in the Perameles, excepting in the Chceropus, where the functional and fossorial fingers are reduced from three to two. It is in rela- o tion to this condition, doubtless, that the clavicles are wanting in these genera, while all other Marsupials possess them. In these 14 ANATOMY OF VERTEBRATES, the biceps has the usual two origins : the flexor sublimis digitorum is distinct from the flexor profundus in Didelphys. The muscles of the hinder extremity are chiefly remarkable in the Kangaroo for their prodigious strength and unusual number : the accessory muscle of the biceps cruris, e. g., arises from a caudal vertebra, and, with that from the ischium, forms two strong fasciculi, one inserted into the outer femoral condyle, the other into fascia covering the gastrocnemii. The pyriformis is also a double muscle. The sartorius has its insertion so modified that it becomes an extensor instead of a flexor of the tibia : it is chiefly fixed to the tibial side of the gristly patella, and by fascia into the capsular ligament of the knee-joint and the anterior proximal tuberosity of the tibia. In a Dasyure (Das. macrurus ) I found that the sartorius had a similar disposition and office. In this ambulatory carnivorous Marsupial the external and middle glut&i are so disposed as to extend the thigh, while the in- ternal glutceus inflects and rotates it inward. In a Bandicoot (Perameles lagotis) the sartorius ran nearly parallel with and dermad of the rectus, and was inserted into the upper part of the patella. Besides this sesamoid, which is rarely developed in other Marsupials, I found a thick cartilage attached to its upper part and interposed between the common tendon of the recti and vasti, removing that tendon further from the centre of motion, and in- creasing the power of the extensor muscles of the leg. The rec- tus femoris has its two origins very distinct, and its homotypy with the biceps of the upper extremity is obvious. Thegracilis is a very thick and strong muscle. The biceps flexor cruris in the Perameles is a muscle of very great strength ; it terminates in a strong and broad aponeurosis, which extends over the whole anterior part of the tibia, being attached to the rotular tuberosity of that bone, and terminating below in the sheath of the tendo Achillis, whereby this muscle becomes an extensor of the foot. All the equipedal Marsupials, whether burrowers as the Wom- bat, climbers as the Koala, Phalangers, and Opossums, or simply gressorial, as the Dasyurida, have the tibia and fibula so connected together as to allow of a certain degree of rotation upon each other, analogous to the pronatory and supinatory movements of the bones of the antibrachium, and the muscles of the leg present corresponding modifications. None of the analogous carnivorous, pedimanous, or rodent Placentals present this condition of the hind leg. In the Kangaroo, the gastrocnemii almost rival those of Man in the bulk of the fleshy part. In the Dasyurus macrurus, \heplantaris, instead of rising from MUSCULAR SYSTEM OF MAMMALIA. 15 the femur, has its fixed point in the fibula, from the head to half- way down the bone, fleshy ; its tendon passes obliquely inward, and glides behind the inner malleolus to its insertion in the plantar fascia, so that it rotates the tibia inward besides extending the foot. The soleus has an extensive origin from the proximal to near the distal end of the fibula. There are, as usual, three deep- seated muscles at the back of the leg. Of these three the muscle homologous with the tibialis posticus is readily recognised; its tendon glides behind the inner malleolus, and is inserted into the inner or tibial cuneiform bone. The muscle Avhich has the relative position and origins of the flexor longus pollicis., sends its tendon by the usual route to the sole of the foot, where it di- 5 vides and distributes a flexor tendon to all the toes except the rudimental hallux ; it has the same disposition in the Opossums, where the hinder thumb or great toe is fully developed : for this modifica- tion, however, the Compara- tive Anatomist is already pre- pared by meeting with such common office of the muscle in the first step from Man, viz. in the Orang, Gorilla, and Chimpanzee. The third deep-seated mus- cle, being situated internal to the two preceding ones, may be the homologue of \\\Q flexor digitorum communis longus ; it nevertheless sends no ten- don to the toes nor even to the tarsus, but its fibres pass from the tibia obliquely outward and downward be- tween the preceding muscle and the interosseous ligament to the fibula, where they are -, . , . -. Muscles of leg, Phalangista exclusively inserted so as to oppose the plantaris and rotate the foot outward. This muscle closely adheres to the interosseous fascia, and thus resembles in its 16 ANATOMY OF VERTEBRATES. attachments the pronator quadratus of tlic fore limb : it is most developed in the pedimanous climbing Marsupials, where the rotation of the foot is more frequent and extensive. Fig. 5 shows this modification of the muscles of the hind-foot in the Phalangista vulpina ; a, is the expanded tendon of the sartorius ; byffracilis', c, seinitcndinosus ; and d, semimembranosus ; both these muscles are inserted, as in many other quadrupeds, low down the tibia : c, gastrocnemius ; f, plantaris ; g, the homologue of the flexor lone/us pollicis pedis ; h, tibialis posticus ; this muscle divides and is inserted by two tendons, h' and h" , into the internal and middle cuneiform bones ; /, the rotator muscle of the tibia. In the muscles on the anterior part of the leg, the extensor brevis diyitorum has its origin extended into this region, and is attached to the outside of the fibula. There are three peronei\ the external one is inserted into the proximal end of the fifth metatarsal : the tendon of the middle peroneus crosses the sole in a groove of the cuboid like the peroneus longus : the internal peroneus is an extensor of the outer or fifth toe. The Perameles layotis, among the saltatorial Marsupials, presents a different condition of the extensors of the foot from that above described. The yastrocnemii, soleus, and plantaris all arise above the knee- joint, and the tendon of the plantaris, after sheathing the tendo Achillis and traversing the long sole, is finally inserted into the base of the metatarsal bone of the fourth or largest toe ; thus this muscle, which is strongly developed, bends both this toe and the knee, while it extends the foot. In the Kangaroo the flexor of the toes rises from the outer tuberosity of the tibia, its fleshy part covers the back of the leg beneath the soleus, the tendon passes to the sole and divides into a large tendon for the principal toe, fig. 211, iv, a smaller tendon for the outer toe, v 9 and a still smaller tendon which goes to the two slender inner toes. The muscle seems to combine the homo- logues of the flexor liallucis and flexor diyitorum, with, perhaps, also that of the tibialis posticus. 195. Muscles of L,issencephala. -The Rodentia closely re- semble the Marsupialia in their muscular system ; with like modifications according to the absence or presence of clavicles, and to the gradatory, saltatory, scaiisorial, and fossorial move- ments of the species respectively. They have not the marsupial modifications of the cremaster and abdominal muscles, nor the rotatory muscle of the tibia ; but certain Rodents show pecu- liarities of the masseter which will be noticed in connection with the organs of mastication. MUSCULAR SYSTEM OF MAMMALIA. 17 The Insectivora afford examples of special muscular develope- ment in the fore part of the trunk and pectoral limbs of the Mole, fig. 6, and in the muscles which act upon the prickly skin of the Hedgehog, figs. 7 and 8. The dermal muscles are powerful and extensive in all Insec- tivora : in the Mole ( Talpa europcea) 9 fig. 6, the insertion of one of these is seen at a : it assists in retracting the trowel-like Muscles of the fore part and limbs of a Mole (Talpa europcea). XLIII. fore limb ; and, when this is the fixed point, draws forward the pelvis and thigh. The muscles of the scapula are singularly de- veloped and modified : the trapezius operates upon the short base of the elongate bone with great advantage. The anterior portion, d, arising from the occiput, derives further strength from the ossi- fied ' nuchal ligament,' and is inserted at e : the part answering to the posterior fibres of the muscle, f, arises as far back as the lumbar vertebne to be similarly inserted into the base of the sca- pula, antagonising the former. The f splenius capitisj A, derives fibres from the nuchal style, as well as from certain dorsal and cervical vertebra? : it is inserted into the paroccipital region of the cranium. The stemo-mastoid, g, joined by a ( cleido-mastoid ' from the cubical clavicle, is a very powerful muscle which expands to be inserted into the lateral part of the superoccipital and fascia covering the mandibular angle. The deltoid, k, coextensive with VOL. I IT. C 18 ANATOMY OF VERTEBRATES. the scapula, acts through its length with great power upon the well-developed humeral ridge. The s teres major,' /, commencing at the thickened base of the scapula, and deriving fibres from the lower facet of that triedral bone, combines to be inserted into the humerus with part of the latissimus dorsi, m ; a strip from which muscle is extended to the olecranon. The triceps, o, arising from both scapula and humerus, is extremely broad and thick, calling for an extended olecranon for adequate insertion. Part of the powerful flexors of the hand (j#. diyitorum, q, Jl. carpi ulnaris, r), and part of the extensors, t, are shown in this view. The pectoralis consists of five thick fasciculi, four of which rise from the sternum, and one from the clavicle : they converge to be implanted into the great humeral ' crista pectoralis : ' to these is added a fasciculus of which the homologue may be traced in Cetacea and Unyulata, passing transversely from one insertion of the pectoral to the other, and serving to combine both trowels in vigorous fossorial action. Of the muscles of the jaws the ' tem- poralis ' is shown at b 9 and the ( masseter ' at c. The Hedgehog (Erinaceus] manoeuvres its armour of spines by means of powerfully developed and specially arranged cutaneous muscles. By putting any part of the integument on the stretch, the spines are erected, and their points held firm against the assailant : by the same act of stretching the skin, the proportion Dermal muscles of the Hedgehog. XLIII. thereof to which the prickly armour is restricted can be drawn over ihe whole of the exposed surface of the animal, which in this act rolls and squeezes itself into the shape of a ball. In fig. 7, the Hedgehog is dissected as in the ordinary posture, or unrolled. The layer of muscle, , a, a', consists of concentric fasciculi, thin over the middle of the back, , and becoming thicker toward the periphery, ', a' , which is well defined. All the MUSCULAR SYSTEM OF MAMMALIA. 19 fibres are closely attached to the derm, and to the fibrous cap- sules of the roots of the spines. To the circumference of this circular muscle are attached shorter ones at right angles : a pair of these, b, arise from the caudal diapophyses, pass forward and expand to interblend with the posterior periphery : a second pair, d, with attachments to the nasal and premaxillary bones, pass backward over the forehead to the anterior periphery : a third pair, e, arising from the fore part of the sternum, pass for- ward and outward, diverging, and ascending in front of the shoulder to the antero-lateral part of a. A muscle, c, from fascia external to the mandibular angle, ascends between the auditory meatus and the eyeball, and combines with d in operating on the fore part of the great orbicular muscle. TVhen the Hedgehog assumes its offensively defensive position it bends and retracts the head and draws forward the pelvis, curving the back, as in fig. 8 : the converging slips b, c, d, e, pull down the orbicular muscle, which relaxes to slip over the projecting parts: the peripheral part, a', #', having descended below these, contracts, and encloses the head, limbs, and body, in an orbicular form. In resuming the normal position the sphincter relaxes, the head is rotated forward, the pelvis and tail are drawn back, the limbs begin to extend themselves: the orbicularis, ', a', is pushed up beyond the meridian, and then contracts, dispos- ing itself, after full exten- sion of the parts beneath, upon the dorsum of the animal, as in fig. 7. Su- perficial sheets of muscle, extending from the shoulder joint backward, s, and over the abdominal region, g, concur with the above-de- scribed in the motions of rolling and unrolling the animal. One of the lateral muscles of the snout is shown at m, the masseter at c. In the order Bruta the most notable modifications of the mus- cular system are met with in the Anteaters. c 2 8 Orbicularis dermal muscle, Hedgehog, half unrolled. XLIII. 20 ANATOMY OF VERTEBRATES. On reflecting the skin from the under part of the head in Myrmecophaga jubata, there is seen a feeble developement of a panniculus carnosus in the form of thin transverse fasciculi occurring at intervals of from two to three inches, where they underlie the rami of the slender elongated under-jaw. These muscular strips (dermogulares) have their attachments exclusively in the integument, and aid in accommodatino; its movements to O 9 O the alternating expansion and contraction of the great gular dila- tation near the base of the tongue. The transverse fasciculi are crossed by a longitudinal strip of cutaneous muscle (dermo- labialis posticus) on each side of the under part of the head and neck ; the strip emerges from beneath the fore part of the great subpectoral gland ; it diminishes in breadth and increases in thickness as it extends forward, assuming near the mouth the character of a muscle independent of the skin, where, passing beneath the tendon of the retractor anguli oris, it is inserted into, or blends with, the fibres of an accessory portion of the orbi- cularis oris. A shorter longitudinal muscular strip (dermolabialis anticus) arises from the integument below the fore part of the preceding muscle, becomes free as it advances, and is inserted into the proper orbicularis oris. The flattened and slightly separated fasciculi of the dermo- abdominalis arise from the fascia covering the anterior and in- ferior part of the sternum and contiguous sternal ribs ; also from a median raphe of the subcutaneous fascia, attached to the linea alba, and extending two-thirds of the way towards the pubis. The anterior two-thirds of the above muscular sheet are joined by a broad layer of similar flattened fasciculi covering the side of the thorax, and the muscle so formed passes obliquely downward and outward, converging to form a thick fleshy band, about two inches broad, which is continued along the inner and upper part of the thigh, and becomes slightly twisted prior to its attachment to the aponeurosis covering the knee-joint. The posterior portion of the dermo-abdomina.lis consists of thinner and more scattered flattened fasciculi which pass outw T ard and downward, and, as they diverge from the median line, are lost in the subcutaneous fascia covering the tendinous expansion of the obliquus externus abdominis. Between the dermo-abdomi- nalis and the proper abdominal muscles there is a moderately thick layer of elastic cellular tissue. In the dissection of the head -of the Great Anteater, three pairs of long and slender muscles are met with, which relate to the o 7 movements of the head. MUSCULAR SYSTEM OF MAMMALIA. 21 The sternocervicalis arises from the upper and outer angle of the mauubrmm sterni, close to the inner (mesial) side of the sternomaxillaris, by a thin tendon, which soon becomes fleshy, and the slender muscle gradually contracts to be inserted into the fourth cervical vertebra. The sternomastoideus arises from the outer angle of the manu- brium sterni, by a tendon which, at one inch from its origin, becomes a fleshy flat muscle ; this gradually increases in thickness to a rounded form, then contracts, and forms a tendon inserted into the paroccipital. The sternomaxillaris arises from the inner side, near the upper and outer angle of the manubrium sterni, and from the manubrial fascia, central of the clavicular fascia, and of the origins of the sternomastoideus and sternocervicalis. Its origin is by a flat short tendon : an aponeurosis passes from one tendon to that of the fellow muscle. The fleshy part forms a long slender band, which passes forward, and, about four inches from its origin, sends off a slender fleshy strip to the ceratohyoideus. It then advances as a slender round fleshy muscle, which degenerates into a sub- compressed tendon about half an inch in length, opposite the compressor salivaris. Resuming its fleshy structure, it forms an anterior subcompressed belly, ten inches in length, and from four to five lines in diameter. This gradually contracts, and terminates in a slender tendon three inches long, which expands to be in- serted into the outer and under part of the maxillary ramus, six inches in advance of the angle of the jaw. To the action of the pair of muscles so inserted is mainly due that characteristic movement of the head of the Great Anteater when it composes itself to sleep, and draws its head downward and backward between the fore-limbs, in contact with the chest. The mouth is small, and susceptible of so slight an opening as not to require for that action the usual modification of this part of the sterno-cleido-mastoideus muscle. The proper muscles of the jaws consist of the temporalis, the masseter, and the pterygoidei. The chief peculiarities of the muscles in the present species relate to the unusual developement and movements of the tongue. The mylolnjoideus is of unusual extent, and is divisible into different portions : two of these represent the normal mylohyoideus, and extend from the sym- physis mandibulae backward as far as the ascending ramus of the jaw. A third portion arises fleshy from the inner side of that ramus, whence its fasciculi radiate toward the middle line, in a somewhat twisted course, the anterior ones passing beneath the 22 ANATOMY OF VERTEBRATES second or normal part of the mylonyoideus. The fourth portion at its anterior part arises from the angle of the jaw, then from the base of the cranium, and afterward from a strong fascia extended thence backward, between the post-cranial prolon- gations of the nose and month ; the posterior and longest fasci- culi come off more outwardly, and radiate to spread over and blend with the gular fasciculi of the sternoglossi, passing out- ward and downward, and then bending inward to envelope that part of the hyoid apparatus. All the fibres of the fourth portion terminate in a median raphe, which is less marked than in the anterior portion. The fibres of the posterior division of the mylohyoideus, especially those which are attached to the under surface of the posteriorly prolonged nasal canal, form a kind of muscular sheath for the basal part of the muscles of the tongue. The cerato-hyoideus arises from the cerato-hyal : its fibres converge and form a fasciculus which is inserted into the commis- ^ sural tendon of the genio-hyoid, and is connected with a strip from the sternomaxillaris. After mvino; attachment to the fore- o o going two muscles, and to the anterior constrictor of the pharynx, its extremity is attached to the stylo-liyoideus muscle. In most mammals the hyoid arch, by the length of the ossified part of the stylohyal and the extent of the ossification of the ceratohyal is almost restricted to hinge-movements forward and backward upon the proximal joints of the stylohyals as a fixed point ; so that the basihyal with the tongue cannot be very far protruded or retracted. In the Myrmecophaga jubata the usual place of the stylohyal is occupied by a long and slender muscle, the styloliyoideus, which arises from the petromastoid, and after a course of five inches is inserted into the ceratohyal, here the first bone of the hyoid arch. Supposing the stylohyoideus to contract one-third of its length, it would protract the hyoid arch to the same extent : in which act it combines with the geniohyoideus. The retraction of the hyoid arch is provided for by the sterno- thyroidic and their continuations, the thyrohyoidei. ^^geniohyoideus arises by a single tendon from the symphysis of the jaw, runs back beneath the raphe of the anterior mylo- hyoideus, slightly expands beneath the raphe of the middle mylohyoideus, then again contracts and again expands, and at about ten inches from its origin becomes diffused into fleshy fibres, which gradually acquire a breadth of six lines, continue back in close connection with the mylohyoideus to the commissural tendon, and there expand, the lateral borders being attached MUSCULAR SYSTEM OF MAMMALIA. 23 thereto. Here a mid-line of separation appears, and the muscle bifurcates into two flat fasciculi, which are inserted into the angles of the basihyal. The sternothyroidei, fig. 9, /?, p, come off from the sixth, seventh, and eighth sternal bones, and from the seventh and eighth sternal ribs near their articulations therewith. The in- terthoracic extent of these muscles is six inches. Behind the manubrium the left muscle sends off a small fasci- culus of fibres to the right one, and the right reciprocally to the left. Where the decussation takes place there is a tendinous intersection at the fore part of the muscle. In advance of the interchange of fasciculi the ster- nothyroidei diverge and emerge from the chest, beyond which cavity they are fleshy throughout their extent, and are inserted into the lower and fore part of the thyroid cartilage. Sternoglossus, ib. g, /. This remark- able muscle arises fleshy from the lateral border of the dilated xiphoid and last sternal bone, arid from its junction with the last two true ribs. Linear tendinous intersections mark the part of the muscle within the chest. Emerging from beneath the manu- brium, it advances as a flat fleshy mus- cle. Opposite the hyoid it is perforated by a lingual artery, between four and five inches in advance it is perforated by the lingual nerve, h, and here its in- ferior stratum is resolved into flattened fasciculi of fibres which decussate or combine with those of the opposite muscle. About six inches in advance of the basihyal these fasciculi spread over a dilated membranous portion of the buccal cavity, at the lower part a 1 Ili X - y\ of Tongue.. Great Anteater. 24 ANATOMY OF VERTEBRATES. of which the base of the tongue is situated, and here they con- verge and blend with corresponding flattened fasciculi, sent off from the lower part of the genioglossi, as these pass backward to the base of the tongue. The main continuation of the stcrno- glossus, ?, forms a rounded slender muscle, which raises the buccal membrane so as to form the back part of the fnenum lingua?, penetrates the back part of the base of the tongue, and constitutes a great proportion of its substance. The gcnioylossus., ib. m, n, o, has a complex origin, by a middle portion, from the short symphysis mandibulse, and by a flattened penniform series of fibres, form the lower border of the mandi- bular rami for the extent of four inches behind the symphysis. The symphysial origin is round and slender, and belongs more directly to the proper tongue-muscle : the ramal origins seem to be the more special fixed point of the subgular fasciculi. The fibres of the latter origin pass obliquely backward and inward, con- verging to a middle raphe, to which the symphysial origin closely adheres. The two origins of the muscle are blended into one for about three inches beyond the point of attachment, in which extent the muscle forms a moderately thick depressed mass along the middle of the under part of the mouth. It then begins to expand, and to detach from its under surface those subgular fasciculi, which diverge and imite with the corresponding dis- memberments of the sternoglossi. The main part of the genio- glossus enters, as a single muscle, the fore part of the base of the tongue, carrying into the floor of the mouth a fold of buccal membrane forming the fore part of the fraenum linguae. Beneath the insertions of the geniohyoidei, a pair of more slender muscles, epihyoglossi, come off from the median ends of the epihyals. These muscles, after a brief course, expand into a thin layer, resolve themselves into separate fasciculi, and combine an inch in advance of their origin to form a layer about eight lines in breadth below the middle line of the post-lingual part of the mouth, which layer slightly diminishes in size as it approaches the commissure of the sternoglossi, and, with them, penetrates the back part of the fraenum linguas. 196. Muscles of Cetacea. In the Cctacea the muscles of the trunk are chiefly developed : those of the limbs are restricted to the pectoral pair. Swimming is the principal mode of progres- sion in the muticate orders of Gyrencepliala : but the phytophagous Sirenia have the power, in order to feed upon marine or littoral plants, of crawling at the bottom of the sea and shuffling along MUSCULAR SYSTEM OF MAMMALIA. the shore bv means or aid of their anterior members, which in the & true Cetacea are exclusively natatory organs. The head, in these, has so little mobility, that its axis can be but slightly altered, without that of the body altering also. With bones so short, so little mobile, and extensively co-adapted or anchylosed, as the vertebrae of the neck, muscles proportionately reduced should correspond. The cervical muscles are, neverthe- less, much the same in number as in other Mammals ; but their shortness and thinness, principally in those attached to the atlas and the axis, are extreme. The homologue of the ( splenius capitis,' fig. 10, h, is the best developed: it comes off from the anterior dorsal and cervical series of neural spines, and its fibres converge to be inserted into the paroccipital ridge. The muscles of the back present no other important modifica- tions than their great developement, especially where they are prolonged upon the caudal vertebras. Thus the longissimus dor si and the sacro-lumbalis are attached anteriorly to the skull, and posteriorly transmit their tendons, the first to the end of the tail, the second to all the transverse processes of this part of the spine, associating its movements, especially in the vertical direction, with those of the back. The levator caudcs, takes its rise above the five or six dorsal vertebra?, under the longissimus dorsi, and often in this part blends with it ; it then extends freely as far as the ex- tremity of the tail, Avhere the two muscles unite together again by their tendons. They are opposed by a depressor caudce, of great thickness, which proceeds from the thoracic region, attached by tendinous slips to the ribs and the contiguous transverse processes ; it is inserted into the haemal arches of the tail. A muscle passes from the rudimeiital bones of the pelvis to the haamapophyses of the anterior portion of the tail. The great recti abdominis and obliqui ascendentcs muscles are continued backward from the ab- domen, and attach themselves behind to the sides of the anterior caudal vertebrae. By this aggregation of muscles the tail of the Cetacea expands to proportions of the trunk, and acquires the prodigious strength which it possesses for propelling the most gigantic of the species, with ease and swiftness, through the water ; and, by means of the horizontal expansion of the caudal fin, it enables them to readily ascend to the surface to respire and again seek protection in the deep abysses of the ocean. In the great pectoral muscle, part of which is shown in fig. 10, at g, the costal origin is extensive, and the portion which comes off from the short sternum, passing transversely each to its own 26 ANATOMY OF VERTEBRATES. humerus, closely resembles the transverse connecting fasciculus in the Mole. The muscle answering to ' levator scapulae,' b, rises from the paroccipital, as well as from the cervical diapophyses : it ex- pands to be inserted into the fore and upper angle of the scapula 10 Muscles of pectoral fin, Ddphinus. and the fascia covering the s infraspinatus : ' it is a protractor, or forward rotator, of the scapula. The ' rhomboideus,' a, is the raiser of the blade-bone. Two strong muscles attached to the paroccipital and mastoid, pass, one, e, to the sternum (sterno- mastoideus), the other to the humeral tuberosity (sterno-hume- ralis). The ( latissimus dorsi,'/", is short and slender, coming off by a few digitations from the ribs, and inserted into the humerus and by an extended aponeurosis into the olecranon. The ( supra- spinatus ' is small : it is covered by the f deltoid,' i. The ( infra- spinatus/ c, is a broad and thin sheet of muscle. Behind it is a ' teres major,' k, also of broad and flat form ; and a thick and narrow ( teres minor,' /. The ' serratus magnus' does not extend forward beyond the ribs of the dorsal vertebra?. In the Ungulate series the muscular system has been traced out in both Perisso- and Artio-dactyle species, but most com- pletely in the Horse, figs. 11- 13. In this sensitive quadruped the dermal muscles are well developed, enabling it to shake the MUSCULAR SYSTEM OF MAMMALIA. 27 whole skin, rattling the harness which may be attached thereto., and to vibrate particular portions on which an insect or other irritant may have alighted. This ' panniculus carnosus ' is thick upon the neck, whence it passes downward, becoming ( aponeu- rotic ' upon the fore-limb : the sheets upon the sides and fore part of the trunk send a flat tendon to be inserted, with that of the latissimus dorsi, into the humerus : and other fasciculi pass downward over the muscles of the antibrachium, and 11 Myology of the Horse, ii". terminate in a fascia! expansion over the carpo-metacarpal seg- ment. The posterior part of the panniculus spreads over the loins, and, descending, degenerates into an aponeurosis, which forms, in the male, a sheath for the penis: the hinder portion encases the rump and thigh in a strong carneo-aponeurotic covering, which accompanies the fascia lata to the hind leg. On removing the panniculus carnosus, the superficial proper 28 ANATOMY OF VERTEBRATES. muscles of the trunk and limbs are exposed, as in the side view, %. 11. The ' spinalis dorsi ' repeats closely the characters of that muscle in Man. Its continuation, the ' spinalis ccrvicis,' is in the Horse of great strength and importance : its origin commences from the second dorsal spine, which origin is continued for about one-third of the way down that spine toward its root : it arises likewise from the third dorsal spine and the ligamentum nucha? ; from these origins it runs forward to be implanted by strong and distinct ten- dons into the spines of the anterior cervical vertebra?. The ' longissimus dorsi ' is situated immediately external to the spinalis, taking its origin from the common mass of muscle that arises beneath the lumbar fascia, as well as from the spinous pro- cesses of the loins and sacrum, whence it runs forward to be in- serted by a double set of tendons into the transverse processes of the loins and back, and also into the posterior ribs near their angles. Its continuation, the e transversalis colli,' consists of very powerful fasciculi, inserted respectively into the diapophysial parts of the last five cervical vertebrae. The ' sacro-lumbalis ' arises, in conjunction with the latissimus dorsi, from the back of the sacrum, and also by flat tendons from all the ribs, except two or three of the most anterior ; and its slips are inserted by as many distinct tendons into the inferior edge of all the ribs, except two or three of the hindmost, and also into the transverse process of the seventh cervical vertebra. The continua- tion of this muscle, the f cervicalis ascendens,' is chiefly remark- able for the strength of its tendinous insertions into the middle vertebra? of the neck. The ' multifidus spina?,' in the dorsal region, arises by numerous tendons from the metapophyses of the sacral, lumbar, and dorsal vertebra? ; each slip running forward to be inserted into the neural spine of the vertebra in front of that from which it derives its origin, the whole forming a thick mass, which fills up the hollow situated between the spinous and transverse processes. In the neck a similar disposition exists. Besides the ' intertransversarii colli,' there is a series of muscles arising from the prezygapophyses of the first dorsal and five last cervical vertebra?, and inserted, severally, into the side of the centrum in advance : they are called by Stubbs e intervertebrales/ 1 The ( longus colli ' arises from the transverse processes of the third, fourth, fifth, and sixth vertebra? of the neck, from which origins it runs upward to be inserted by distinct tendons into the MUSCULAR SYSTEM OF MAMMALIA. 29 anterior part of the bodies and transverse processes of the vertebrae above them, and into the anterior surface of the atlas. The muscles which raise or straighten the tail are the following : The f sacro-coccygeus superior ' arises from the third and suc- ceeding sacral spines, and from those of the anterior caudal vertebra?. The fleshy mass formed from these origins gives off numerous slender tendons : the first of these is the shortest, and runs inward to be inserted into the base of the first caudal vertebra, in which the articular apophyses are wanting. The second tendon is in- serted in a similar manner into the succeeding vertebra ; the third into the next, and so on to the end of the tail. Each tendon is lodged in a sort of ligamentous canal, which forms a sheath for it o o * throughout its whole course. When these two muscles act in concert the tail is raised. The ' interspinales superiores ' form a continuation of the inter- spinous series of vertebral muscles ; but as the spinous processes of the tail are short, and soon replaced by tubercular rudiments of the neurapophyses, these muscles are here disposed obliquely, being more widely separated posteriorly than they are in front. The muscles which depress the tail all take their origin in the interior of the pelvis, and are prolonged to a greater or less extent along the inferior aspect of the tail. They form four pairs of series of muscles, called the f ileo-coccygei,' and ( sacro-coccygei inferiores ; ' the latter are the more direct antagonists of the sacro- coccygei superiores, and their tendons are received into sheaths resembling those upon the upper surface of the tail, and are inserted successively into the base of each caudal vertebra, begin- ning about the seventh. The muscles adapted to move the tail laterally are arranged in two sets ; the ( ischio-coccygei externi,' a few fibres of which, in the Horse, are connected with the termination of the rectum and the ( intertransver sales.' The muscles derived from the vertebral column which serve im- mediately for the movements of the cranium have nearly the same origins as in the human subject, but are comparatively of much greater strength, owing to the inclined position of the head with respect to that column. They may be divided into such as pro- ceed, 1st, from the atlas ; 2nd, from the axis ; and, 3rd, from the posterior cervical vertebra? and ligamentum nuchre. To the first set belong The s rectus posticus minor,' ( rectus anticus/ ( rectus lateralis/ and c obliquus superior.' 30 ANATOMY OF VERTEBRATES. The muscles derived from the axis are the ( rectus posticus major ' and the ' obliquus inferior.' The ' complexus ' commences from the prezygapophyses of the third cervical vertebra, continues its origin from all those of the neck below that point, as well as from those of the first dorsal : also by a strong tendon from the transverse processes of the second and third dorsal vertebra? : from these origins it runs forward to be inserted by a strong round tendon into the super-occipital close to its fellow of the opposite side : in this course it is connected by numerous tendinous processes with the ligamen- tum nuclia?. The ' trachelo-mastoideus ' arises from the oblique processes of the third, fourth, fifth, sixth, and seventh cervical and first dorsal vertebra?, and from the transverse processes of the second and third vertebra? of the back ; it runs forward external to the last- mentioned muscles to be inserted by a strong tendon into the paroccipital. The above muscles are overlapped by the ( splenius capitis,' which, arising by strong tendinous processes from the spinous processes of the two superior dorsal and two last cervical, and also extensively from the ligamentum nucha?, runs forward to be inserted into the transverse processes of the fifth, fourth, and third cervical vertebra?, and into the transverse ridge of the super- occipital. The muscles of the ribs and sternum present, in the Horse, a disposition little differing from that of the corresponding muscles in Man : they are the ' scaleni,' the ( intercostals,' the ( levatores costarum,' the ' serratus posticus,' d, and ' serratus anticus,' /, and the ( triangularis sterni,' the two latter of which must be regarded as depressors of the ribs, and consequently acting the part of muscles of expiration. The walls of the abdomen are composed of five pairs of muscles, to which the same names are applicable as are bestowed upon them by the anthropotomist ; but the rectus abdominis is much more extensively developed. Arising from the os pubis, it passes forward enclosed in its usual sheath to be inserted into the ensi- form cartilage and into the cartilaginous terminations of the third, fourth, fifth, sixth, seventh, eighth, and ninth ribs, and also into the sternum between the cartilages of the third and fourth ribs. There are even fleshy fibres derived from this muscle prolonged as far forward as the articulation between the first rib and the sternum. Muscles of the anterior extremity. The ( trapezius ' consists MUSCULAR SYSTEM OF MAMMALIA. 31 of that part only which is called the ascending portion in the human subject, and which is inserted into the posterior margin of the spine of the scapula. The ' sterno-mastoid ' is present, but the ( levator anguli scapula?,' the cleido-mastoid, and the clavicular portions of the trapezius and deltoid are all replaced by the muscular expansion which, taking its origin from the par- occipital and from the transverse processes of some of the superior cervical vertebra, passes downward in front of the head of the humerus and descends along the inner surface of the fore-arm, into which it is ultimately inserted. The ( trachelo-acromialis ' arises from the transverse process of the atlas and of the four following cervical vertebra?, descends toward the shoulder-joint, making its appearance externally between the two divisions of the trapezius, which it separates ; it then spreads out over the acromial portion of the scapula, and descends as far as the middle of the humerus. This muscle draws the shoulder upward and forward in the Tapir, and is implanted into the apoueurosis which covers the deltoid : while, in the Horse, it has its insertion into the middle portion of the humerus by two aponeurotic tendons, which embrace the brachialis internus muscle. The ( serratus major anticus ' arises from the transverse pro- cesses of the third, fourth, fifth, and sixth cervical vertebra?, and also from the external surfaces of the six superior ribs : its origins extending as far backward as the insertion of the tendons of the sacro-lumbalis : from this extensive origin it passes backward around the chest to be implanted into the base of the scapula, its insertion occupying nearly half of the internal surface of that bone. It forms, with its fellow on the opposite side, a kind of sling, by which the trunk is suspended. The ' pectoralis minor ' is represented by a muscle, which, arising from the sternum and from the first, second, third, and fourth ribs near their sternal terminations, runs upward and backward to be inserted into the superior costa of the scapula near the base of that bone ; it also contracts tendinous attachments with the aponeurotic covering of the teres minor and other scapular muscles. The ( rhomboideus ' arises entirely from the ligamentum nucha?, and from the spines of the anterior dorsal vertebra?, whence it runs outward to be affixed to the base of the scapula. The ( omo-hyoideus ' is represented by a strong muscular fasci- culus, from the coracoid tubercle. 32 ANATOMY OF VERTEBRATES. The f sterno-mastoideus,' or stcrno-maxillaris, arises from the anterior end of the sternum, and, running forward strong and fleshy, is inserted by a flat tendon into the inferior maxilla underneath the parotid gland, sending, however, another tendon to be im- planted into the root of the paroccipital. Muscles inserted into the humerus. The e pectoralis major,' from the aponeurosis of the external oblique, from the two hinder thirds of the sternum ; and from the fore part of the ster- num. The first of these portions winds round to be inserted into the head of the humerus ; the second ends in a fascia, which descends over the fore-arm, while the third, running in a transverse direction over the inferior portion, is inserted into the humerus along with the ( levator humeri pro- prius' between the biceps and the brachialis inter- nus : a part of the sternal portion joins the corre- sponding portion of the opposite side to form the ( muscle common to both arms,' by the action of which the two fore-legs are made to cross each other. The f latissimus dorsi ' is powerfully assisted in its action by the cutaneous muscle already described, a strong tendon from which is inserted into the humerus along with that of the latis- simus dorsi. Both are intimately connected with the tendon of the teres major, and from this combination of tendons arises one of the heads of the triceps extensor cubiti. The ' supraspinatus,' the t infraspinatus,' the i subscapularis,' the ' teres major,' and the f teres minor/ with similar attachments, Myology of the Horse, ii". MUSCULAR SYSTEM OF MAMMALIA. 33 differ in their proportions from those in the human subject, dependent upon the shape of the scapula. The ' deltoid ' extends forward in nearly the same direction as the infraspinatus, and has been named by hippotomists the 4 abductor lono-us brachii.' The l coraco-brachialis ' takes its o oristin from the tubercular remnant of the coracoid situated C upon the superior costa of the scapula : the biceps has but one origin, with which the coraco-brachialis is in no way con- nected. The s brachialis interims,' fig. 12, w, has the same arrangement as in the human subject: it is the ' short flexor of the fore-arm.' The 'triceps extensor cubiti,' fig. 11, c, consists of three portions similar to those named in the human anatomy the Ions; extensor, the short extensor, and the brachialis ex- c? ternus: there is also a fourth portion, derived from the common tendon of the latissimus dorsi and teres major, by the inter- vention of which it takes its origin from the inferior margin of the scapula. As might be expected from the construction of the bones of the forearm, both the proiiator and supinator muscles are wanting. The ( extensor carpi radialis,' fig. 11, a, b, is here single, arising from the anterior part of the external condyle of the humerus, and from the external surface of that bone for a considerable distance: it forms a strong fleshy belly, terminating in a powerful tendon, which runs to be inserted into the base of the anterior surface of the metacarpal. This muscle seems, from the extent of its origin, to represent the long supinator and the two radial extensors of the wrist combined, and all three thus co-operate in the extension of the wrist. There is but one 'flexor carpi radialis,' fig. 12, p; it arises from the external condyle of the humerus, and is inserted into the posterior surface of the base of the metacarpal, forming the antagonist to the preceding muscle. The ' flexor carpi ulnaris ' arises from the posterior part of the external protuberance of the os humeri, and also by a distinct head from the protuberance situated above the internal condyle ; its tendon is inserted into the pisiform bone and into the base of the rudimentary metacarpal beneath it. The f extensor carpi ulnaris' arises from the posterior part of the external condyle of the humerus, and is inserted, like the preceding, into the os pisiforme, whence it is prolonged beneath the carpus, so as to perform the office of a flexor of the wrist. The e extensor com- munis digitorum,' fig. 11, k, arises from the external condyle of the humerus and from the contiguous fascia, also from VOL. III. D 34 ANATOMY OF VERTEBRATES. the upper and lateral part of the radius ; its fleshy belly is strong, and terminates in a single tendon, which runs over the foot to be inserted into the last phalanx, having previously 13 Ligaments of the fore-limb, Horse, ir 14 28 Deep muscles of the thigh and ligaments of the pelvic limb of the Horse, ii". given off a slip to join the tendon of the extensor minimi digiti. The ( extensor proprius minimi digiti ' is represented by two muscles : one of these, called the ( extensor of the pastern/ fig. MUSCULAR SYSTEM OF MAMMALIA. 35 11, q, is inserted by the intervention of a strong tendon into the side of the first phalanx of the functional toe. The second muscle, placed between the above and the preceding muscle, furnishes a similar tendon, which, after passing in front of the carpus, becomes united at an acute angle with that of the former, the two co-operating with each other in extending the foot. The tendon of the ' abductor longus pollicis ' is implanted into the internal surface of the base of the metacarpal, so that it thus becomes an extensor of the foot : it is the ' oblique extensor of the cannon ' in Hippotomy. The ' flexor digitorum sublimis perforates ' and the f flexor profundus perforans ' arise in com- mon from the internal protuberance of the os humeri, and the two are confounded together for a considerable distance, when the two muscles separate to form two distinct tendons ; of these, that belonging to the flexor sublimis, fig. 12, Z, m, runs beneath the annular ligaments of the carpus, to be inserted into the base of the proximal phalanx, previously dividing to give passage to the tendon of the profundus, i s on its way to be implanted into the last phalanx. The following are the principal ligaments of the fore-limb, fig. 13 ; a, the ' post-scapular,' c, the ( prescapular,' which extend the base of attachment of scapular muscles ; b, the ligamentous band strengthening the fore part of the capsule of the shoulder- joint ; k, similar ligaments strengthening the capsule of the elbow-joint ; e, e, internal lateral ligaments of the successive joints ; d, ' pisiform ' ligament ; c, ligament from the inner splint-bone (metacarpal n) to the sesamoid behind the metacarpo- phalangial joint ; o, ' outer cartilage of the hoof; ' p, inner cartilage of the hoof. Muscles of the hind-limb. The ectogluteus is a comparatively slender muscle, deriving its principal origin from the sacral fascia, but also reinforced by a long slender fasciculus, which descends immediately from the upper portion of the ilium. Its insertion is into the third trochanter and external rough surface o at the upper part of the thigh bone, and also by strong tendinous apoiieuroses into the fascia lata. The ( mesogluteus,' fig. 11, v, is the principal muscle in this region ; it arises extensively from the sacro-iliac aponeurosis, and from the external surface of the ilium ; it is implanted into the outer surface of the great trochanter, and is prolonged, by means of a strong posterior fasciculus, toward the lower extremity of the femur. The other muscles inserted into the great trochanter namely, D 2 3G ANATOMY OF VERTEBRATE 8. the c entogluteus, 5 fig. 12,/, the ' quadratus femoris,' the c obturator extcrnus,' the ' obturator interims,' the 6 gemclli,' and the f pyra- uiidalis '- -present a disposition similar to that which they have in the human body. The muscles passing between the pelvis and the lesser tro- chanter, and also those that arise from the pubis to be implanted into the internal surface of the thigh, are the ' psoas magnus,' the ( iliacus,' the ' pectmseus,' and the ' tri])le adductor,' fig. 12, p. The flexor muscles of the leg are the ' biceps flexor cruris,' the ' semimembranosus,' the ' semitendinosus,' the ' sartorius,' the ' gracilis,' and the ' poplitaeus,' all of which are enclosed by the dense fascia of the thigh, which is kept tense by the action of a 6 tensor vaginae femoris.' The last-named muscle, called also the o 4 musculus fascia? latie,' arises from the anterior portion of the crest of the ilium, whence it descends obliquely downward, en- closed between two layers of the fascia, covering the thigh, into which it is strongly inserted. The extensor muscles of the leg viz., the ' rectus,' fig. 11, A, the ( vastus internus,' fig. 12, 7, the f vastus externus,' fig. 11, n, and the ' cruraeus ' offer in all quadrupeds the same general dis- position as in Man, the three last forming one great common muscle, e trifemoro-rotuleus.' The anterior margin of the thio-h ~ ~ is formed by the ( sartorius,' which here, from its position and office, has been named by hippo tomists the ' long adductor of the thigh.' The ' biceps cruris ' arises by a single origin, which is derived from the ischium, and the neighbouring ligaments and fascial ex- pansions. This muscle covers a large proportion of the outer surface of the thigh : its principal insertion is into the head of the fibula, but it likewise throughout its whole length contracts ex- tensive and important attachments with the fascia lata, so that it also becomes a powerful extensor of the thigh. There is, how- ever, a distinct portion of the biceps derived from the sacro- sciatic aponeurosis, the fibres of which are directed obliquely from before backward, which, meeting the ischiatic portion at an angle, form with it a kind of raphe, which is prolonged for some distance. This muscle is called ( vastus longus ' in Hippotomy. The ' gracilis,' fig. 12, u, is a very considerable muscle; it is called by hippotomists the ( short adductor of the thigh,' whilst they usually give the name ' gracilis ' to the semitendinosus. The ' semimembranosus ' and ( semitendinosus ' have the same origin and general arrangement as in Man ; but both of them are inserted into the tibia by a broad aponeurosis, extending much MUSCULAR SYSTEM OF MAMMALIA. 37 lower down than in the human subject, a circumstance which causes the leg to be permanently kept in a semiflexed condition. The ( gastrocnemius,' fig. 11,6, is relatively less carneous than in Man : the f solaeus ' is slender and feeble : but the ' plantaris,' fig. 12, 13, is remarkably developed ; it arises from the fossa above the external femoral condyle: its tendon, is, is continued down ward, and runs over the extremity of the os calcis, where it is enclosed in a sheath; passing on from this point, it divides, is, to be inserted upon each side of the posterior surface of the proximal phalanx towards its inferior extremity, here giving passage between its two inser- tions to the tendon of the long flexor of the toe, which it serves to bind down closely to the pastern when the fetlock joint is bent, thus seeming to perform the functions both of the ( plantaris ' and of the short flexor of the toes. The 'tibialis anticus,' fig. 12, 37, is implanted into the anterior surface of the base of the metatarsal, so as to be an extensor of that portion of the foot. The ( tibialis posticus ' is seen at 25 and 2t>, fig. 12. The c popliteus,' ib. 23, is a powerful muscle. The three s peronei ' are represented by a single muscle, the tendon of which becomes conjoined with that of the long extensor of the digit, with which, when in action, it co-operates. The flexor muscles are reduced to a state of extreme simplicity ; the short flexor communis is wanting ; the ( plantaris,' as described above, has a double insertion into the base of the great pastern bone, and presents a similar disposition to that of the flexor per- foratus in digitate quadrupeds, while the f flexor communis longus perforans,' fig. 12, 28, here serving a single tendon, 29, appropriated to the solitary toe, passes on as usual to be inserted into the last phalanx, so, 31. The homologue of the ' flexor longus hallucis' exists in the Horse, notwithstanding the absence of the hallux ; but, instead of its usual destination, it here becomes affixed to the tendon of the flexor communis perforans, to which it forms a powerful auxiliary. The ' extensor communis,' fio;. 11, 21, terminates in a single O J O tendon, 25, which is inserted into the dorsum of the last phalanx of the foot : it receives, however, in its course, a few fleshy fibres, w, derived from the metacarpal and representing the * extensor brevis ' of unguiculate quadrupeds. In fio\ 14, showing the chief ligaments of the hind limb, are O O -5 represented the ( iliacus interims/ /, k, I, and the ( epicotyloideus,' <7, a small and peculiar muscle, which arises by a flat tendon, b, from above the origin of the rectus cruris, d, and is inserted at the fore and outer part of the neck of the femur, c, below the head : 38 ANATOMY OF VERTEBRATES. its fibres are attached to the capsular ligament. 21 is the ' rotulo- condylar ligament ; ' 22 the ' rotular ligament ; ' 23 the ' external rotular ligament; ' 10 the e condylo-fibular ligament ; ' 15 the ' ex- ternal semilunar cartilage;' 25 the ' calcaneal ligament ;' 26, 26, the * external lateral ligaments ' of the ankle and succeeding joints ; 27 the ' ant-oblique ligament ; ' 28 the ligament from the outer splint-bone (metatarsal iv) to the sesamoid behind the metacarpo- phalangial joint : ss and 39 are cartilages of the hoof. Muscles of the hyoid arch. The ' sterno-hyoideus ' and the ' sterno-thyroideus ' form a single muscle, Avhich divides to be inserted into both the larynx and os hyoides. The ' omo- hyoideus,' fig. 11, a, is a very strong muscle. The f stylo- hyoideus ' furnishes a sheath to the longer portion of the digas- tricus, and extends from the furcate extremity of the stylohyal to the base of the thyrohyal. There is also a f cerato-hyoideus ' extending between the thyrohyal and the thyroid cartilage. The ' paroccipito-styloideus ' is a short thick muscle, derived from the paroccipital, whence it descends toward the angle of the stylo- hyal, into which it is inserted, above the origin of the stylo- hyoideus. Facial muscles. The ( occipito-frontalis ' has the usual origin from the posterior part of the cranium, whence, running forward, it covers the skull with its tendinous aponeurosis, and, in front, spreads in muscular slips upon the forehead, some of which, fig. 11, 12, extend downward, to spread over those of the orbicu- laris palpebrarum. Situated upon the outer side of the orbit there is another descending slip of muscle derived from the lateral cartilage of the ear, which, by elevating the external canthus of the eye, con- tributes to the expression of that organ. The f levator anguli oris,' fig. 11, n, is inserted into the upper lip and margin of the nostril : it has two origins, derived from the surface of the superior maxillary bone, between which the lateral dilator of the nostril and upper lip passes to its destination. The ' zygomaticus ' is a depressor of the external angle of the eye, as well as an elevator of the corner of the mouth, its fibres being intermixed with those of the orbicularis palpebrarum, as well as of the orbicularis oris. The f long dilator of the nostril, and elevator of the upper lip ' arises at a little distance below the inferior margin of the orbit ; and, passing between the two origins of the levator anguli oris, terminates in a tendon, which becomes connected with that of the opposite side, and then spreads out in front of the upper lip. MUSCULAR SYSTEM OF MAMMALIA. 39 10 Vertical section of the middle or functional digit of the fore- foot of the Horse, ni". From the tendon of the last muscle arises the ' anterior dilator of the nostril/ fig. 11, t, which, acting upon the interior nasal cartilage, powerfully expands the aperture of the nose. The ' orbicularis oris,' fig. 11, o, the 'levator labii superioris,' the ( elevator of the chin,' 15 and the f depressors of the lower lip, and angle of the mouth,' are well developed. The anatomy of the limbs of the Horse would be incomplete without a notice of the structure of the terminal segment of these best of terrestrial locomotive or- gans, in the perfection of which the whole mecha- nical force is concentrated on a single hoof. The longitudinal section of the huge finger that forms the foot or hoof' of the horse, fig. 15, shows the structure of the three phalanges proximal i, middle 2, and distal or ungual 4, with that of the sesamoid, or nut-bone s, adding to the lever-power of the division of the tendon, 7, of the flexor profundus, going to the last phalanx : the insertion of the tendon of the ' flexor sublimis,' 6, and that of the tendon of the common ' extensor,' 5, are also shown. The hoof-box of the ungual phalanx is denser at its periphery, 12, than at its base, 10, but is not continuous over either surface ; the former part is the ( wall,' the latter the ' floor ' of the horny or ' insensible ' hoof. The wall, or f external wall,' has the form of a hollow cone obliquely truncate above, so that it is highest in front, 12, becoming vertical, and lower as it extends backward, losing density, degenerating partly into the elastic tissue, 9, but being mainly inflected inward, toward the centre of the sole, where it tf blends with the horny ( floor,' and forms the ( internal wall : ' this supports the superincumbent softer elastic tissue, and partly that called the ' frog,' fig. 16, 3, for w T hich a triangular space is left between the inflected parts of the ' internal wall.' Thus the posterior part of the periphery and of the floor of the ( hoof is left uncovered by the horny box, which is accordingly free for a certain degree of elastic expansion and contraction, especially posteriorly. The inner surface of the f wall ' is produced into a 40 ANATOMY OF VERTEBRATES. 16 number of subvertical lamella 1 , fig. 17, .3, with which interdigi- tatc corresponding lamella, ib. 17, from the periosteum of the lingual phalanx : the first are called the c horny lamellae/ the second the ' vascular ' or 'sensitive lamellae.' At the interspace between the inflected parts or prongs of the ' wall ' projects the mass of elastic suhcorneous tissue called by the French farriers ' fourchc,' and misnamed by the English ' frog.' In the horizontal section of the hoof, fig. 16, in which a part, 2, is reflected back, the ' frog,' 3, is seen to extend to the centre of the sole : its exposed outer surface is the hardest and most horny ; but this tissue is not so thick as some farriers, misapplying the paring-knife, suppose : it gradually passes into elastic tissue : it is im- pressed at its middle part by the ' cleft of the frog,' and is reflected upon the ( internal wall.' In fig. 16, 2, 6, is the section of the ' wall ;' 3, the upper surface of the ( frog ; ' 4, 4, are the parts of the ' wall ' called the ( heels ; ' 5, parts of the sole called the 'bars;' 7 11 indicate the boundaries of the space lodging the frog ; 12, are the ' vascular Iamella3.' The horny matter of the sole possesses more elasticity than that of the wall : the sole is slightly concave toward 12 the ground, abutting by its lower circumference against the wall : it is cleft to its centre by the triangular / O space through which the frog pro- jects. In fig. 17, i is the skin reflected; 2, soft elastic tissue, with oil, forming a cushion behind the me- tacarpo-phalangial joint ; 3, * wall ' of the hoof turned back, showing the horny Iamella3 ; 4, section of front part of the 'wall; ' 5, 6, ligamentous parts of metacarpo-phalangial joint; 7, tendon of common ' extensor;' 8, 9, 10, those of the deep and superficial flexors ; 15, expansion of the great anterior cartilage of the hoof; IG, the ( coronary frog-band ' reflected ; 17, the ' vascular lamella?; ' 18, elastic portion of the 'frog;' the 'coronary venous plexus' is shown at 10. Transverse section of the Loof of the Horse, in". MUSCULAK SYSTEM OF MAMMALIA. 41 17 19 In the Indian Rhinoceros the panuiciilus carnosus is more discontinuous than in other Perissodactyles, but where it exists is of unusual thickness. One sheet at the side of the thorax sends its fascia into the interstice of the dermal fold in front of the fore limbs. A similar portion be- hind is inserted into the posterior fold of the skin, suggesting that such permanent folds served the pur- pose of affording a firmer insertion to the aponeuroses of the cutaneous muscles than a plane surface could have done. Two sheets of panniculus rise, broad and thick, one on each side of the anterior part of the abdomen from the superficial fascia, and, passing back- ward, terminate in aponeuroses covering knee-joint. As the patelhx) are higher than the line of the abdomen, in the erect position of the animal, the preceding muscles afford additional support to that bulky part, some of the weight thus being trans- ferred to the hind-legs, which, reciprocally, are by these muscles drawn forward in locomotion. 1 198. Muscles of Artiodactyla.--\\\ the Ruminant division of the Artiodactyle Ungulates the ' panniculus carnosus ' is better developed than in the non-ruminant group, e. y. the hog and the hippopotamus. The fixed points from which, in the ox, the Avcll-cleveloped sheets of dermal carneous fibres act on the skin are the scapula, mandible, ilium, pubis, and patella: a 1 V. p. 36. Dissection of the digit forming the Horse's foot. m". 42 ANATOMY OF VERTEBRATES. subjacent layer of fascia allows the play of the tf panniculus' independently of the main masses of the muscular system, fig. 18. To the sheet of carneous fibres spreading from the scapular fascia over the neck the term ' cutaneus colli ' is applied : to a thinner layer extending from the fore part of the neck over the forehead and cheeks to the lips, that of f cutaneus faciei.' The thick layer expanding from the supra-scapular attachment over the shoulder and part of the fore-limb is the ( cutaneus humeri ; ' that which extends from the iliac and pubic fascia lata, and from the patella, forward, expanding upon the abdomen, is the ( cutaneus abdominis : ' the ' musculus preputialis,' in the Bull, is a deriva- tion from the foregoing dermal muscle. The e trapezius,' fig. 18, 10, n, answers to the scapular division of that muscle in Man ; it arises in the Ox from the neural spines of the anterior half of the thorax, and from the f ligamentum nuchse.' In the Giraffe it is in two portions : one arises from the 18 Superficial muscles of the Cow. iv transverse processes of the fifth and sixth cervical vertebrae, its fleshy part is thick and strong but expands as it passes down- ward and backward and finally is lost in a strong fascia over- spreading the shoulder-joint ; the second portion is thin and broad, arises from the ligamentum nuchre, and is inserted into the fascia covering the scapula, 1 The ' masto-humeralis,' fig. 18, 8, 8, may represent the ( cleidal ' part of the trapezius in claviculate Ungulates : it arises by an aponeurosis from the ligamentum nucha3, and, by a tendon, from the paroccipital ; the chief and more superficial portion is inserted into the humerus, the deeper portion into the sternum. The ' latissimus dorsi/ fig. 18, 12, in 1 xcvir. p. 234. MUSCULAR SYSTEM OF MAMMALIA. 43 the Ox, as in the Horse, is a comparatively small muscle, and acts upon both humems and antibrachium. The f rhomboideus,' fig. 19, 9, is not single, as in the Horse and Giraffe, but consists in the Ox of pre- and post-rhomboid portions : the former rises from the nuchal ligament, as far forward as its occipital insertion : the latter from the spines of the two or three anterior dorsals ; both converge to be inserted into the base of the scapula. The ( splenius capitis,' fig. 19, 7, arises from the anterior dorsal and posterior cervical spines ; the fibres diverge to a flat tendon inserted into the paroccipital and the ridge rising therefrom. In the Sheep an insertion of a small fasciculus into the diapophysis of the atlas represents the ' splenius colli.' The ( scaleni ' form three strong muscles in the Camelidce, in the Giraffe four, which rise from the fourth to the seventh cervical vertebra and are inserted into the manubrium sterni and first rib. The s scalenus anticus ' in the Cow is shown at 12, fig. 19. The ( sterno-maxillaris ' arises from the manubrium and divides, at 9, fig. 18, to be inserted into the paroccipital and mandibular angle. 19 Deep muscles of the Cow. iv. The levator anguli scapula?,' fig. 19, 8, arises from the pleur- apophyses of the third and fourth cervical vertebrae, and is inserted into the anterior angle of the scapula : it seems part of the follow- ing muscle. The 'serratus magnus,' fig. 19, 10, has an extensive origin from the pleurapophyses of the anterior half or two-thirds of the dorsal series, forward, to that of the fifth cervical inclusive, by * dentations,' or an angular strip from each : the fibres converge, as- cending beneath the scapula, to be inserted into the cartilaginous suprascapula. Thus, as the fore-part of the trunk is, as it were, slung upon the two great serrate muscles which principally support 44 ANATOMY OF VERTEBRATES. 20 the weight of the deep chest of the Ruminants, the interposition of the elastic cartilages between the upper attachments of the muscles and the capitals of the bony columns of the two fore-legs is attended Avith the same advantage as is obtained by slinging the body of a coach upon elastic springs. The main body of the 'pectoralis major,' fig. 18, is, rises from the sternum and ensiform cartilage, the fibres converging to the O y O O tendon inserted in the outer tuberosity of the humerus : the an- terior derivative from this muscle, effecting the crossing of the fore-limbs, is present in Ruminants as in Solipeds and Cetaceans. Two muscles converge to an insertion answering to that of the f deltoid ; ' one is the superficial portion of the ' masto-humeralis,' fig. 18, 8, fig- 19, 11 ; the other, ib. u, arises from the spine and post-spinal fossa of the scapula : the latter is the proper homologue of the ( deltoid.' The ( supra- or pre-spinatus ' is shown at i, figs. 20 and 21 ; it is inserted by a double ten- don into the fore and inner tuberosities of the humerus : the ' infra- or post-spinatus,' fig. 20, 2, has a single strong insertion into the JD ~ outer tuberosity. The insertion of the ' teres major ' is seen at fig. 20, 3. The subscapularis, fig. 21, 2 and 2 X , con- sists of two chief masses, and corresponds in length and narrowness with the bone from o which it originates ; it consequently produces, like the muscles on the opposite surface of the scapula, more rapid and extensive motion ot the humerus, to the inner tuberosity of which it is attached. The s coraco-brachialis,' fig. 20, 8, arises from the tuberous representative of the coracoid ; its insertion into the humerus ex- tends down to the inner condyle. The ' biceps brachii,' fig. 21, 10, shows an origin from the coracoid as well as the chief one from above the glenoid cavity of the scapula. It is in- serted into the radius, below the usual tuberosity, and also sends a strip of tendon to the antibrachial aponeurosis. In the Camelidce the tendon of origin is double, but approximated, and encloses a sclerous sesamoid as it passes over the head of the humerus. The * brachialis internus ' rises from the neck of the humerus ; its in- IV ?Ju\ 21, is, Muscles of the fore-umb, Cow * . ' from the inner (radial) side. IV". sends its flat and strong tendon behind the cannon-bone, near the lower end of which it divides, and perforates the corresponding divisions of the ' flexor perforatus,' to be inserted into the ungual phalanges of the digits, Hi, iv, fig. 193, Ox, vol. ii. The 'flexor carpi ulnaris internus,' fig. 21, 16, is inserted into the ' pisiforme.' The ectogiuteus, fig. 18, is, arises from the fore part of the ilium and sacral fascia, and is inserted into the lower part of the great 46 ANATOMY OF VERTEBRATES. troclianter ; it is closely connected with the ( tensor fascine femoris.' This muscle, fii>'. 18, ic. arising from behind the outer iliac tube- * O O rosity, expands upon the thigh, and is lost in fascia covering the knee-joint, and attached to the spine of the tibia, whereby the muscle becomes, with the rectus, a flexor of the thigh. There is a 6 sartorius ' crossing obliquely the inner side of the thigh, and in- serted aponeurotically into the inner side of the head of the tibia. The ( mesogluteus,' fig. 19, is, arising from the outer side of the ilium, is inserted into the outer part of the great troclianter. The ' entogluteus,' ib. 19, rises above the acetabulum, and is inserted into the upper part of the great trochanter. The 'biceps femoris,' fig. 18, 17, is, arises from the sacro-sciatic fascia and from the ischial tuberosity ; the fasciculi from both origins unite to form a broad muscle (the ( vastus longus ' of Hippotomy), which is in- serted by a strong aponeurosis into the head of the tibia and fascia of the leg. The 'iliacus interims ' is shown at 17, fig. 19 : 23, 24, and so, ib., are muscles of the tail. The ' vastus externus,' fig. 19, 20, covers the whole of the outer part of the thigh-bone, from the great trochanter ; it is inserted into the patella and head of the tibia ; a small part of the ' rectus femoris ' appears in front of its upper part. The ' gracilis ' is a large broad muscle, arising from the pubic symphysis, and inserted into a long tract of the tibia. The e adductor magnus ' is seen at 27, the e semitendinosus ' at 28, and the ' semimembranosus/ or e adductor tibia? longus,' at 29, fig. 19. The last two muscles are blended in the Hog. The 6 tibialis anticus ' arises from the inner side of the fore part of the head of the tibia by a strong tendon ; the muscular part swells into the chief of those on the fore part of the leg ; the tendon of inser- tion splits to give passage to that of the ' peroneus longus,' and is inserted into the outer side of the head of the metatarsal. There is an extensor of the middle phalanx of each functional toe ; the tendon of the long f extensor digitorum' bifurcates at the end of the metatarsus for insertion into the ungual phalanx of the same toes. The chief peculiarity of the flexors of the digits of the hind-foot in hoofed quadrupeds is the accession of muscles not so applied in most other mammals. Thus the i gastrocnemius.' besides its inser- CJ * tion into the heel-bone, sends a strong tendon along the back of the metatarsal, to the phalanges, where it expands and bifurcates, each division again splitting for the passage of that of the ' flexor perforans,' before being inserted into the middle phalanges. In like manner the homologue of the l tibialis posticus ' combines its ten- don with that of the ' flexor perforans ;' such common tendon MUSCULAR SYSTEM OF MAMMALIA. 47 expanding behind the metatarsal, and splitting to perforate the tendon of the preceding flexor in its way to the last phalanx. Of the abdominal muscles, the f obliquus externus ' is shown in fig. 18, 14; its broad tendon is perforated by the mammary artery and vein, at 19. The ( obliquus interims ' is seen at 16, fig. 19. I found the following conditions of the hyoid muscles in the Giraffe i 1 - -The ' mylo-hyoideus,' thick and strong, arose from the internal surface of the lower jaw, and was inserted into the raphe dividing it from its fellow of the opposite side. It ad- hered firmly to the ( genio-hyoideus :' this arose by a well marked tendon from the symphysis menti, and had the usual insertion. The ( genio-glossus ' arose by a tendon close to the inner side of the tendon of the ( genio-hyoideus ; ' its fleshy belly had a considerable antero-posterior extent, and diminished to a very thin edge at its anterior margin. The ' digastricus ' had the usual origin, and was inserted, broad and thick, into the under side of the lower jaw. The { stylo-hyoid ' was remarkable for the slenderness and length of its carneous part. The most interesting modifications in the muscles of the os hyoides were found in those which retract that bone. The muscle which, as in some other ruminants, combines the offices of the ' sterno-thyroideus ' and ' sterno-hyoideus,' arose by a single long and slender carneous portion from the anterior extremity of the sternum ; this origin was nine inches long, and terminated in a round tendon, six inches long ; the tendon then divided into two, and each division soon became fleshy, and so continued for about sixteen inches ; then each division again became tendinous for the extent of two inches, and ultimately carneous again, when it was inserted into the side of the thyroid cartilage, and thence continued in the form of a fascia to the hyoid. This alternation of contractile with non- contractile tissue gave a striking example of the use of tendon in limiting the length of the contractile part of a muscle to the extent of motion required to be produced in the part to which the muscle is attached. Had the sterno-thyroideus been continued fleshy as usual from its origin through the whole length of the neck to its insertion, a great proportion of the muscular fibres would have been useless ; for as these have the power of shorten- ing themselves by their contractility one-third of their own length, if they had been continued from end to end in the sterno- thyroidei, they would have been able to draw the larynx and hyoid one-third of the way down the neck ; such displacement, however, is neither required nor indeed compatible with the 1 xcvir. p. 232. 48 ANATOMY OF VERTEBRATES. mechanical connections of the parts ; but, by the intervention of long and slender tendons, the quantity of the contractile fibre is duly apportioned to the extent of motion required for the larynx and os hyoides. The ' oino-hyoideus ' was adjusted to its office by a more simple modification ; instead of having a remote origin from the shoulder-blade, its fixed point of attachment was brought for- ward to the nearest bone (the third cervical vertebra) from which it could act upon the hyoid to the due extent. In all Herb Ivor a the muscles more directly worked in masti- cation, c. g. the ( masseter ' and ( pterygoidei,' are proportionally more developed than the biting muscles, e. g. 6 temporales ; ' but there are degrees of difference ; in those Ungulates in which the canines are most developed, as e.g. the Hog and Camel tribes, the temporal muscles are larger. In all Ungulates the chief depressor of the jaw, or opener of the mouth, passing from the paroccipital to the mandibular angle, has a single fleshy belly ; it is, however, the homologue of the ( digastricus ' in Man. One of the muscles proceeding from the neural arches of the dorsal vertebrae to the occiput is tendinous, along a portion of its mid-course, in most unguiculate Mammals : it is called ( biventer cervicis ' in Aiithropotomy. Contiguous muscular fasciculi ex- tending from the neural spines of the anterior dorsals to those of more or less of the cervical series, are termed ' spinalis cervicis.' The pair of fibrous masses with like attachments, but in which the striated fibre is almost wholly reduced to the yellow elastic tissue in Ungulates, is commonly known as the ( ligamentum nuchae.' In the Giraffe this mechanical stay and support of the long neck and head commences from the sacral vertebra?, and receives fresh accessions from each lumbar and dorsal vertebra, as it advances forward ; the spines of the anterior dorsal vertebrae become greatly elongated to afford additional surface for the attachment of new portions of the ligament, which appears to be inserted, on a superficial dissection, in one continuous sheet into the longitudinally extended but not elevated spines of the cer- vical vertebra}, as far as the axis ; the atlas, as usual, is left free for the rotatory movements of the head ; the ligament passes over that vertebra to terminate by an expanded insertion into the occipital crest. It consists throughout of two bilateral moieties. In the specimen I dissected, the nuchal ligament, in situ, measured 9 feet in length : an extent of 6 feet was re- moved, which immediately contracted to 4 feet. In the Camel the ligamentum nucha? arises, broad and thin, from the anterior dorsal spines, but gathers substance as it advances and MUSCULAR SYSTEM OF MAMMALIA. 49 becomes condensed into a pair of cords which receive accessions from the cervical spines, by which the ligaments seem bound down so as to follow the curve of the neck : the insertions are into the superoccipital. Posteriorly a continuation of the ligament may be traced spreading out and losing itself in the base of the single hump of the Dromedary, and as far back as that of the hind hump in the Camel. 1 The relative size and insertions ( cervical, b nuchal) of the ligamentum nuchie of the Elephant are shown in fig. 22. Much of the same kind of yellow elastic tissue is combined with the aponeuroses of the abdominal muscles in the Elephant, Rhino- ceros, 2 and Giraffe, in reference to the capacity and heavy con- tents of parts of the alimentary canal. Lignmontnm nuchae, Elephant. 199. JWuscles of Carnivora.- -The commencement of certain facial muscles that reach their full developement in Man may be discerned in the IJnguiculates. Small detached sheets of muscular fibre, ( cervico-facial ' or ( platysma inyoi'des,' are attached to the skin at the side of the neck, spread upon the lateral inte- guments of the face, and, in the Cat, show a special arrangement or developement by affording a muscular capsule to the bulb of each long hair of the whiskers, upon the chin, lips, cheeks, and eyebrows, to which they give the impressive movements of those sensitive parts. Both the ( occipital ' and ( frontal ' parts of the human ' occipito-frontalis ' are also present in the Cat The muscles of the jaws in Carnivora are chiefly remarkable for the large proportional size of the ( temporalis,' with which the ' masseter,' by the more vertical disposition of its fibres than in Herlrivora, combines in the act of forcibly closing the mouth. The ( pterygoidei ' are small and not very distinct from each 1 vi. 2 v . p. 36. VOL. I IT. E 50 ANATOMY OF VERTEBRATES. other. The ' digastric ' is a powerful muscle and seemingly ' mo- nogastric,' but many tendinous filaments in the middle of the carncous substance indicate the division which is established in higher Gyrcnccphala. In the Lion it arises by a strong tendon from the paroccipital ; and its action may be seen in the effort the animal makes to disengage the mandible from ligamentous O cj O parts of its food. In the Felines the latissimus dorsi has its chief insertion into the tendinous arch, bridging over the biceps, and, with the f dcrmo-humcralis ' similarly inserted, it acts upon the inner side of the upper part of the humerus, but sends a strong aponeurosis between the external and scapular ' heads ' or por- tions of the triceps to be continued upon the antibrachial fascia : in the Dog, a distinct fasciculus of the muscle combines its tendon with that of the s scapular ' portion of the triceps. In the Seal- tribe the retractile action of the latissimus dorsi is extended, by the aponeurotic insertion, to the palmar aspect of the pectoral fin. The homologue of the 6 serratus posticus superior ' is largely developed in the Lion, extending its anterior attachments to the nape. The ' protractor scapulae ' arises in Felines from the diapophyses of the atlas, axis, and third cervical, and is inserted into the spine of the scapula near the acromion. The origins of the f great pectoral muscles ' interblend and cross each other in Felines, so as to seem to form a common adductor muscle of the fore-limbs ; but the mass of the fibres resolves itself into four almost distinct muscles, answering to the t large pectoral ' and grand pectoral of Hippotomists, and including the ( sterno- trachiterien ' and ( pectoantebrachial ' of Straus-Durckheim. The ( pectoralis minor ' in the Dog is inserted into the upper part of the glenoid cavity of the scapula. In unguiculate, and especially claviculate, Gyrencephala, the deltoid conforms by the greater extent of origin and size to the more varied movements of the humerus, as compared with the ungulate order. In the Cat the deltoid consists of an anterior portion arising from the acromion, and a posterior one from the spine, of the scapula : in the Bear only the acromial portion is developed. In noncla- viculate Carnivora the ' masto-humeralis ' is present: in cla- viculate species the ( cleido-cucullaris ' and ' cleido-mastoideus ' are its divisions : the former, in Felines, rises from the paroccipital crest, and from the neural spines of the anterior cervicals, passes back and down to the transverse ligamentous tract in which the clavicular ossicle is developed; the ' cleido-mastoid ' is inserted into two outer thirds of the clavicular bone, Avhence is continued a fleshy belly descending along the fore-part of the brachium, in MUSCULAR SYSTEM OF MAMMALIA. 51 front of the biceps, to be inserted into the tuberosity of the radius : it answers to 8, fig. 18, in Ungulates. The biceps, in Felines, derives its single head from the upper rim of the glenoid cavity, and is inserted into the bicipital tuberosity of the radius. The ' brachialis interims ' is a long muscle on the outer side of the humerus, and is inserted into the lower wall of the sigmoid cavity of the ulna. The ( triceps extensor ' is represented by three or more muscles, distinct in their fleshy part, and remark- able for their volume in Felines : their common tendon incloses the olecranon like a strong capsule. Besides the foregoing there are three shorter extensors, one of which is represented by the human ( anconeus ; ' but all belong to the same system as the tricipital extensor. The ( pronator teres ' is proportionally large : in the Lion its carneous part extends far down the fore-arm : in the Cat it ends in the tendon inserted about half way down the radius. The ' palmaris longus ' is also more developed than in man. The e supinator longus,' on the other hand, has a short and slender fleshy portion ; and this relates to the habitual prone position of the paw in Carnivora. The flexors and extensors of the carpus and manus closely accord with those of Man, but with excess of fleshy fibres in the larger Felines ; and a minor degree of distinction of some muscles, as, e. independent ( indicator ' has not yet come about. The ' flexor sublimis ' is a powerful muscle and the principal bender of the paw in ordinary locomotion ; its origin is restricted to the humerus ; its insertions are extended into all the five digits by the fasciae attached to the sides of the metacarpo-phalangial joints, as well as the ordinary perforated tendons into the sides of the first and second phalanges. The f flexor profundus ' arises by five heads from the antibrachium, which form a common flattened E 2 52 ANATOMY OF VERTEBRATES. tendon, along the carpus ; this first detaches a tendon to the lingual phalanx of the pollex, and, at the metacarpus, divides into the four tendons similarly inserted into the four long digits. In each the insertion, fig. 36, b, is into the lever-like process from the palmar part of the bone of the last phalanx. It is this muscle which overcomes the retractile force of the elastic ligaments, ib. , of the claws, and concentrates the power of all five upon the part seized. There is no separate ' flexor longus pollicis.' In the hind limb of Felines, the psoas and iliacus": are more obviously parts of the same muscle than in Man : a fasciculus of the ' psoas ' sends a tendon to the pubis ; but the mainjbody of the muscle acts upon the inner trochanter. In the Cat a detachment of the small ectogluteus descends to be inserted into the patella. The much longer mesogluteus has five origins from lumbar, sacral and caudal vertebra, and from the crista ilii : its tendon goes to the great trochanter. The ' gracilis ' is relatively large. The muscle at the foremost part of the thigh, in Felines, ansAvers to the f sartorius ' and ' rectus femoris ;' there is also a ' tensor fascia?,' which sends an aponeurosis over the fore part of the knee-joint and a tendon to the inner part of the head of the tibia. The f biceps flexor cruris ' receives a slender' accessory fascicule from an anterior caudal vertebra ; besides its normal in- sertion it is continued by fascia into the e tendo achillis.' In the Lion, a special muscle, ' caudo-femoralis,' from the same vertebrae is inserted by its own long tendon into the outer condyle of the femur. The Bear has not the latter muscle. The largest part of the ' gastrocnemii ' muscles is at or near to their femoral origins : the tendons of each are at first distinct, and finally blend by ex- pansions which spread over the calcaneum. The soleus is small, and rises from the fibula : its tendon unites with that of the gastrocnemius externus. The tendon of the ' plantaris ' combines with that of the l short flexor ' of the toes to augment the power of bending their phalanges : its fleshy part is relatively much greater than in Man. 200. Muscles of Quadrui?iana.--In this series, up to the apes, the panniculus carnosus exists ; but is reduced to a thin sheet of carneous fibres from the dorso-lumbar fascia, spreading over the latissimus dor si, and again degenerating to fascia attached to the inner side of the humerus. The f platysma myoi'des ' begins to be defined, in the Aye-aye, as a pair of broad thin layers, arising from pectoral and clavicular fascia, and ascending over the front and sides of the neck, mandibular rami, and cheeks. In the Grants O and Chimpanzees it supports the large cervico-pectoral air-sac communicating Avith the larynx. MUSCULAR SYSTEM OF MAMMALIA. 53 From the Aye-aye to the Gorilla, 1 with a few exceptions, there is a s cleido-mastoideus ' as well as a ( sterno-cleido-mastoideus ; ' but in some Baboons (Macacus} the distinct fasciculus from the clavicle has not been found. In an Orang I found the cleidal part inserted into the diapophysis of the axis vertebra. The term ( digastricus ' is applicable to that mandibular muscle in all Quadrumana, although the partition by tendon of the ante- rior from the posterior belly is not complete in many. In most, as in the Aye-aye, the anterior portions of the pair occupy the anterior interspace of the mandibular rami. The middle tendi- nous part is attached to the hyoid, except where it is feebly marked, as in Stenops. The intermediate tendon of the omohyoid is not found save in the higher tail-less Apes. In all Quadrumana the power of the arms in drawing up the trunk is increased by the accessory muscle from the ordinary ten- don of the ' latissimus dorsi,' which extends its action from the upper to the lower end of the humerus (interior condyle), and to the olecranon. The ( rhomboidei ' extend to the occiput in Maca- ques, Baboons, and the Orang. The 'protractor scapulae* (' acro- mio-trachelien,' Cuv.) exists in most Quadrumana below the Apes; in these the s levator anguli scapula? ' is distinct from the f serratus nragnus ; but is the fore part of that muscle in Baboons.' In the Gibbons (Hi/lobates) the two portions of the 'biceps flexor cubiti' are more powerful and unite lower down the lumerus than in other Quadrumcma, and the inner portion derives an origin from near the pectoral ridge of the humerus : their common tendon is inserted beneath the radial tubercle, and into the antibrachial fascia. In Stenops the biceps has only its 'long head' or origin : that from the coracoicl process is, at least, not distinct from the coraco-brachialis. The f triceps extensor cubiti ' is complicated in Quadrumana by the accessory fasciculus in connection with the tendon of the latissimus dorsi. The lower portion of the f internal head ' of the triceps has also a distinct origin or fasciculus from the ento- condyloid ridge in Chiromys and Tarsius ; in Stenops it arises more from the back part of the humerus. The deep and superficial flexors of the fingers are distinct, but a remnant of that blending which exists in most lower mammals may be seen in the short connecting tendon which in the Aye-aye 2 passes from the ulnar belly of the s flexor sublimis ' to the division of the ' flexor profundus,' giving off the tendon to the middle finger. The fleshy part of both flexors, but especially of the deeper one, is continued nearer to the hand, in Lemuridce and most other 1 cir. p. 30, pi. xi. fig. 1, 22 d. 2 cir. p. 34, pi. xi. fig. 4, e. 54 ANATOMY OF VERTEBRATES, Quadrumana, than in Man, thus enabling the muscles to continue their action as finger-benders -when the hand itself is flexed. The fasciculus of the f flexor profundus ' which sends the tendon to the last phalanx of the thumb, is more distinctly a * flexor longus pollicis ' in Apes than in lower Quadrumana. In the Aye-aye it adheres to the supplementary carpal and fascia on its way to the thumb, and thus opposes both the last phalanx and the ' pad ' at the base of the thumb in the act of grasping. The ' flexor brevis,' the ( abductor,' the ' adductor,' and * opponens pollicis ' are present in the Chimpanzee and Gorilla, as are like- wise the ' extensor longus ' and ' extensor brevis.' In the Orang these muscles begin to be confounded ; in most lower Quadru- mana they are blended together. The homologue of the 'extensor indicis' of Man bifurcates and sends a tendon to both the index and medius digits; the homologue of the extensor minimi digit! likewise splits and sends a tendon also to the annularis ; so that, while in Man the index and minimus only have two extensor tendons, all four fingers (ii v) have them in most Quadrumana. The hand is thereby the stronger as a suspensor of the body from a bough. The ( ectogluteus ' is feebly developed compared with that in Man : the Gorilla, though receding far in this respect, recedes the least. The homologue of the ( gracilis ' is relatively larger in all Quadrumana than in Man, and its insertion is extended lower down the leg. In Stenops the vastus externus contributes a fasciculus to the rectus femoris ; in Chiromys it is as distinct as in higher Quadrumana. But here the mesogluteus exceeds the ectogluteus in size, although the latter is supplemented in the Gorilla by fleshy fasciculi from the ischial tuberosity, which spread their insertions from that of the ectoglutseus down the femur to the internal condyle, apparently representing the adductor magnus. In both Orang and Chimpanzee a muscle from the outer border of the ilium to near the acetabulum is inserted into the under and outer part of the great trochanter and rotates the thigh inwards. 1 The gastrocnemii have a greater length and minor breadth and Thickness of the fleshy part : the soleus rises from the fibula exclu- sively, and joins the gastrocnemii low down. 201. Muscles of J3imana. - The myologies of Anthropotomy reduce the need of noticing human muscles here to some com- parison with those of highest Apes, bringing out the ordinal characteristics of the limbs, and to the illustration of those si vino; o o expression to the face and reflecting the action of the organ that marks Man's place in Creation as the type of a distinct sub-class. 1 ' Scausorius,' Trail, xxxv . ' luvcrtor femoris,' xxxiv. p. 68. MUSCULAR SYSTEM OF MAMMALIA. 23 10 Figures 23 and 24 give a view of the superficial muscles and tendons of the fore-arm and hand of a full-grown male Gorilla and Man of correct relative size. The portion of the triceps is seen in the Gorilla at 2" ; in Man at 5', in whom the origins of the carneous fibres of that part from behind the inter-muscular septum are continued lower down the humerus. The ( brachialis anticus ' is seen at 4, fig. 23, and 17, fig. 24. This muscle is not so completely differentiated from the deltoid and supinator longus in the Gorilla as in Man, nor so individualised as a single muscle : its two portions being more distinct. The biceps, fig. 23, 3, maintains in Man more of its full fleshy character to the sending off of the tendon, 3', to the rough posterior margin of the tuberosity of the radius, gliding over the anterior smooth surface of that process with an intervening ( bursa.' The aponeurosis, 3", sent off to the fascia of the fore-arm crosses the ' pronator teres.' This muscle, 8, fig. 24, is attached to the outer side of the radius below the middle of the bone in the Gorilla, but rather above it in Man. The double origin, viz. from the inner humeral condyle and the coronoid process of the ulna, is better defined in Man, fig. 23, 6. The ( palmaris longus,' fig. 23, 8, arising as a distinct muscle in Man from the inner humeral condyle, is a fasciculus, 5, of the 'flexor carpi ulnaris ' (3, fig. 24) in the Gorilla ; but, as this muscle is subject to variation, and sometimes absent in Man, it may shoAV analogous inconstancy in the Go- rilla. The flexor carpi ulnaris is inserted into the pisiforme in both Man and Ape, but the Muscles of the fore-arm and hand, fleshy and tendinous parts are better defined, and the latter relatively longer and more slender in Man, fig. 23, 9. The flexor carpi radialis arises in Man, fig. 23, 7, from the inner condyle, from the antibrachial fascia and septa continued there- from between the pronator teres, 6, and palmaris longus, 8 ; but in the Gorilla, fig. 24, 4, it derives a considerable accession of 13- 10 -Ik 12 15- 15. ANATOMY OF VERTE CRATES. 24 fibres directly from the radius, and its tendon is shorter and much thicker than in Man. In both it passes through a pulley pro- vided by the trapezium to its insertion into the base of the metacarpal of the index. The tendon of the supina- tor longus in the Go- rilla, fig. 24, 4', is also shorter and thicker, and is not crossed, as in Man, by the exten- sors of the metacarpal and first phalanx of the pollex (fig. 23, n and 12) before its in- sertion into the styloid process of the radius. Part of the carneous mass of the flexor sub- limis dis;itorum is seen o at is, fig. 23, and o', fig. 24. External to this a greater pro- portion of the flexor profundus appears in the Gorilla, fig. 24, 6, than in Man, fig. 23, 15. The flexor longus pollicis, fig. 23, 14, ex- pends its force in the Gorilla, fig. 24, 20, upon both the pollex and index, furnishing tendons to the distal phalanx of each, but the largest and most direct beino; that to the o index. There are mo- Muscles of the fore-arm and hand, Gorilla, i". dificatioilS of minor importance in the origin of this muscle which tend to give it a MUSCULAR SYSTEM OF MAMMALIA. 57 character of being part of the system of the ' flexor profundus' in the Gorilla. The relations of the tendons of the superficial and deep flexors to each other and to the digits are much alike in Man and Ape, but the tendons are relatively broader, and their restraining and strengthening sheaths and bands stronger GJ o o ^^ in the Gorilla ; those formed by the oblique decussating liga- mentous fasciculi, as in the mid-finger of fig. 23, are more distinctly shown in Man than in the Ape. The muscles acting on the metacarpal and first phalanx of the pollex fig. 24, 22, 'abductor,' ib. 24, flexor brevis, ib. 25, adductor -- are longer and more slender in the Gorilla. The abductor in Man is shown at fig. 23, 17. In the Gorilla the ' abductor minimi digiti ' is shown at fig. 24, 10 ; the ' flexor brevis ' at n ; the tendon of the flexor profundus at 13; that of the e flexor sublimis ' at e'. Two of the ' lumbricales ' are shown at 14 and 28, and one of the interossei at 27, fig. 24. The carneous part of the common extensor of the fingers is continued to the wrist in the Gorilla ; three strong tendons go to the second, third, and fourth digits, and a fourth, less strong, to the fifth digit. This digit also receives the tendon of an extensor minimi digiti, and the index a small ten- don of an 'indicator' which is more completely blended with that of the ordinary extensor, besides being more feeble, than in Man. The extensors of the metacarpal, first and last phalanges of the pollex, are present in the Gorilla, but of smaller size than in Man. In the Gorilla the portion of the biceps cruris derived from the ischiadic tuberosity, and inserted, fig. 25, 4, into the outer part of the head of the tibia, is more distinct than in Man from that, ib. 5, derived from the femoral linea aspera and inserted into the head of the fibula, and which expands, 5', upon the cnemial fascia. The external gastrocnemius, fig. 25, 7, continues longer distinct from the internal, and both present longer but narrower and thinner carneous portions than in Man. The soleus, ib. 8, arises exclusively from the fibula and is much narrower than in Man, where it also derives fibres from the oblique line of the tibia and from the middle third of its internal border. The margins of the tendon of the soleus first unite with those of the gastrocnemius, the middle part continues distinct to near the calcaneum. The plantaris has not been met with in the Gorilla. The peroneus longus, fig. 25. 9, has a longer carneous and shorter but thicker O " & O tendinous part in the Gorilla than in Man : the course and insertion of the tendons are the same. The peroneus brevis, 58 ANATOMY OF VERTEBRATES. 25 ih. iy, very closely repeats the characters of that muscle in Man. The 'tibialis anticus,' fig. 25, 17, commences by a broader and more fleshy origin, but gradually decreases as it descends, not swelling out into the well-marked 'belly/ as in Man: the tendon divides more distinctly and deeply to be inserted into the metatarsal of the hallux and the entocuneiforni bone. The extensor longus digitorum, with the same relations at its origin to the tibialis anticus and peroneus longus as in Man, divides, after pass- ing under the annular ligament, into three, instead of four tendons ; the innermost of which subdivides to sup- ply the second and third toes. The extensor longus hallucis sends its ten- don to the last phalanx of the hallux, as in Man. The short extensor of the toes, ib. 20, also sends off a strong fasci- culus, 2(/, the tendon of which acts upon the proximal phalanx of the hal- lux. Three other fasciculi send ten- dons to the second, third, and fourth toes. The long flexors of the toes are dis- tinguished in the Gorilla, as in lower Quadrumana, by their relative posi- tion at the back of the leg. The one toward the inner or tibial side sends its tendon through a strong liga- mentous synovial sheath behind the inner malleo- lus to the sole, where it divides into three chiel tendons which are con- nected with those of the ' flexor accessorius.' In nV. 26, the divisions of o * the long tibial flexor, i, are cut and reflected ; \a ^^^^ goes to the fifth toe ; 4 is the perforated tendon of the fourth toe, 4', reinforced by carneous 21 20 Muscles of the leg and foot, Gorilla. MUSCULAR SYSTEM OF MAMMALIA, 59 fibres from the deeper surface of the main tendon ; \b is the ten- don to the last phalanx of the second toe. 27 26 IV Muscles of the foot, Gorilla. r - . Muscles of the foot, Man. The long fibular flexor of the toes, arising from the back part, of the fibula and interosseous ligament, grooves by its tendon the posterior part of the tibia, the astragalus and the calcaneum, and divides at the sole, fig. 26, 2, into the perforating tendons of the hallux, 2c, the third, 2Z>, and the fourth, 2#, toes. The portion of the flexor brevis which rises from the calcaneum divides into two tendons which form the perforated ones of the third, 3', and second, 3", toes. The short muscles giving the grasping power to the hind thumb are, s, ' abductor hallucis,' 9, * flexor brevis hallucis,' 10 ' adductor obliquus hallucis,' and n, ' adductor trans- versalis hallucis.' The lumbricales and interossei are powerfully developed. In the Orang the long fibular flexor sends no tendon to the hallux. The ordinal modification of the hind- or lower- limbs for the whole work of sustaining and moving the body, in Bimana, is accompanied by well marked and considerable modifications of the toes, the chief of which are illustrated by comparison of the figure, 26, from the highest ape, with fig. 27. The long 60 ANATOMY OF VERTEBRATES. fihular flexor now becomes the ' flexor longus hallucis,' and con- centrates its force exclusively on the tendon, 2, 2c, which goes to the last phalanx of the hallux, z; this tendon is twice the size of any of the divisions of that of the long flexor on the tibial side. This is limited to the function implied by the name 'flexor longus digitorum pedis,' its tendon, fig. 27, i, sending off successively the perforating tendons to the second, third, fourth, and fifth toes. In fig. 27, are shown the insertion of the 'tibialis posticus,' 15; the 'flexor brevis minimi digiti,' 7 ; the ( flexor brevis pollicis,' inserted into the outer, 9, and inner, 10, sesamoids, the adductor pollicis, 8, and the peculiar ( transversalis pcdis,' 10, arising from the under surface of the distal and of the fifth metatarsal, crossing three of the other metatarsals, to be inserted into the outer side of the proximal phalanx of the hallux, blending there with that of the e adductor pollicis.' The heel being the lever-power by which the whole superincum- bent weight of the body is raised in the peculiar ' walk,' or bipedal gait, of Man, muscles that are distinct in quadrupeds are here, contrary to ordinary rule, blended, or have a common insertion. Not only the outer and inner gastrocnemius, but the soleus, and even the plantaris, might be regarded as so many origins of the same muscle, which combine and concentrate their forces upon the calcaneum. The f panniculus carnosus' of quadrupeds is reduced in Bimana to the f platysma myoides,' fig. 28, p, p, p, which extends from the upper and fore part of the chest upward over the front and side of the neck to the mandible and lower part of the face, where the two muscles meet below the symphysis. The middle fibres are attached to the base of the jaw, and posteriorly ascend to the fascia of the masseter ; the anterior ones ascend with the depressor anguli oris and quadratus mexiti to the lower lip and angle of the mouth. In many instances there is a strip from the parotid fascia which converges to this angle, and constitutes the ( risorius san- torini.' The platysma draws down the lower part of the face, or, by a slighter action, the lower lip : the ' risorial ' slip tends to raise the angle of the mouth. Most of the muscles of the face are attached at one part to bone, at another to skin or to some other muscle. The skin of the human face is remarkable for its tenuity, flexibility, and abundant supply of vessels and nerves; its vascu- larity tinting the cheeks and lips : it is more adherent and the subjacent cellular tissue is denser along the median line than at other parts. The ' orbicularis oris,' fig. 29, o o, has no attachment to bone. MUSCULAR SYSTEM OF MAMMALIA. 61 It consists of two semi- elliptic planes of muscular fibres which surround the mouth and interlace on either side with those of the ( buccinator ' and other dilators of the oral orifice. The ex- ternal or peripheral surface adheres to the skin, the internal or posterior surface is covered by the mucous membrane of the mouth. Acting as a whole it closes the mouth, bringing the lips 28 29 nuiccles of the head and neck. Muscles of the face. in contact and pressing them firmly together, but the upper and lower halves can act separately, or the fibres of one side may contract while the others are quiescent, so that different parts of the lips may be moved by different portions of the muscle, which may be regulated or antagonised by the muscles which con- verge to the mouth. A pair of accessory strips to the orbi- cularis, ' accessorii orbicularis superioris,' rise from the alveolar border of the premaxillary, and arching outward on each side are continuous at the angles of the mouth with the other muscles there inserted. A second pair, ' naso-labiales,' descend from the septum of the nose to the upper lip, but with an interval, cor- responding with the depression on the skin beneath that septum. fi-2 ANATOMY OF VERTEBRATES. The 'Icvator labii superioris/ fig. 29, I, arises from the lower maririn of llie orbit, and descends to be inserted into the orbi- o cularis and the skin of the upper lip. The ' levator anguli oris,' fig. 29, c', arises below the snborbital foramen and descends, inclining outward, to the angle of the mouth, blending its fibres with those of the zygomatici and orbicularis. The f zygomaticus major,' fig. 29, 3, is cylindrical, rising from the malar and de- scending obliquely inward to a similar insertion at the angle of the month. The zygomaticus minor, fig. 29, 3, arises in front of the xyg. major, and passing downward and inward to the angle of the mouth, where it is continuous with the outer margin of the levator labii superioris. The levator menti is a conical fasciculus arising from the incisive fossa of the mandible, external to the symphysis, and expanding as it descends to be inserted into the integument of the skin. The ' depressor labii inferioris,' fig. 30, d, arises from the inner half of the external oblique line of the mandible, and is partly also continued from the platysma : its fibres ascend, inclining inward to be attached to the lip, where they blend with those of the orbicularis oris. The ( depressor anguli oris,' fig. 29, t, arises from the external oblique line of the mandible : its fibres ascend and converge to the angle or commis- sure of the lips, blending with the other insertions at that part. The buccinator, fig. 30, b, arises from both upper and lower jaws and the ptery go-maxillary ligament : its fibres line the cheek and converge toward the angle of the mouth, where some decussate, the lower ones going to the upper segment of the orbicularis, the upper ones to the lower segment, while other fibres are continued forward into the corresponding lip. The buc- cinator acts, in antagonism with the orbicularis, in spirting fluids from the mouth and in playing on wind instruments. In mastication the buccinator presses the food from between the cheek and gums into the cavity of the mouth. It assists also in deglutition when the mouth is closed, by pressing the food back- ward. The ' levator labii superioris alaeque nasi ' arises from the nasal process of the maxillary, descends obliquely outward and divides, a short strip being attached to 30 LOCOMOTION OF MAMMALIA. 63 tlie cartilage of the ala nasi, the outer and longer strip to the skin of the upper lip near the nose, and becoming blended with the orbicularis and levator labii proprius. The ' triangularis nasi/ or ( compressor iiaris,' figs. 29, and 30, n, arises from the maxillary external to the incisive fossa : its fibres proceed upward and inward, expanding to an aponeurosis continuous, over the bridge of the nose, with that of the opposite muscle. The f depressor alre nasi ' is a short flat muscle radiating upward from the myrtiform or incisive fossa of the maxillary ; it sends upper fibres to the septum and back part of the alse nasi and lower ones into the orbicularis oris. The ' orbicularis palpebrarum,' fig. 29, o, surrounds the orbit and eyelids : it arises from the internal angular process of the frontal, from the nasal process of the maxillary, and by a short tendon at the inner angle of the orbit. It rapidly expands to form a broad thin elliptical plane of fibres : the palpebral por- tion is thin and pale : the orbital portion is thicker and of a reddish colour. The action of the muscle is that of a sphincter, the curved fibres in contraction approaching the centre : but as thcv are fixed at the inner side the skin to which the muscle is */ attached is drawn toward the nose, and becomes corrugated into folds which converge toward the inner canthus. The ( comiffator O o snpercilii, is a small triangular muscle placed at the inner end of the eyebrow, arising from the same end of the superciliary ridge : its fibres pass upward and outward to be inserted into the under surface of the orbicularis palpebrarum. It depresses the eye- brow, and, in conjunction with its fellow, throws the integuments into vertical folds as in the act of frowning. The 'occipito- frontalis ' consists of an anterior and posterior carneous expansion united by a broad f epicrauial,' aponeurosis. The anterior muscle, fig. 28, f, consists of two lateral portions, each connected in- feriorly with the integument of the corresponding eyebrow, and slightly overlapped by the ' orbicularis.' The posterior or oc- cipital portion, ib. o, also consists of a pair, attached inferiorly to the upper curved line of the superoccipital, and to the mastoid. The fibres are parallel and nearly vertical. The action of this muscle is most apparent upon the skin of the forehead and the eyebrows : it raises the latter and throws the former into trans- verse wrinkles. 202. Locomotion of Mammals. In the movements of the human frame the three kinds of lever are exemplified. Those of the head upon the atlas are on the principle of the first kind, fig. 31, in which the fulcrum F is between the power p and the resistance w. When the body is raised on tip-toe by the action of the ANATOMY OF VERTEBRATES. muscles on the heel-bone, fig. 37, k, the action is that of the second kind of lever, in which the resistance (of the tibia on the astraga- lus), as in fig. 32, w, is between the fulcrum F (afforded by the ball of the hallux), and the power a (tcndo achillis). 31 A y B l'r'''TI'n;-;iT'iiiiiiiii'ii'iiiiL':'iil'riiiiiii-'ii-;ii-.;niiMiiimiiiiiiiiiiiiiiiii!iii.ijiji'ii.-.!Hii'iiiiu'iiiiinin!T 32 F w Lever of the first kind. Lever of the second kind. In lifting a weight in the hand by motion of the fore-arm only, fig. 33, the elbow-joint is bent ; the power (of the flexors of the fore-arm) being applied (as by the biceps, />) at a, between the fulcrum (elbow-joint)^ and the resistance w or b, according to the third kind of lever exemplified in fig. 34. The mechanism of the pulley is exemplified in the passage of the tendons of the peronei muscles through the groove of the external malleolus of the human ankle-joint, in the tendon of the obturator 33 interims gliding through the groove in the os ischii, in the tendon _ of the circumflexus palati passing through the hamular process ot the sphenoid bone, in the tendon of the obliquus superior gliding through the ring attached to the frontal bone, and -in several other instances where a change of the directions of the limbs results from tendons passing over joints, through grooves in LOCOMOTION OF MAMMALIA. 65 bones, or under ligaments, by which the muscles are capable of producing effects on distant organs without disturbing the sym- metry of the body, an effect which, owing to the limited power of contraction in the muscles, could O 4 be accomplished in no other way. The joints in the mammalian skeleton are chiefly of two kinds, ( ginglymoid ' or hinge-joints, and 6 enarthrodial ' or ball-and-socket r" joints. In Man the former are less definitely fitted for motion on one plane than in most brutes. The Lever of the third kind. arm and fore-arm move in concen- tric planes upon the elbow-joint ; the knee-joint allows a certain rocking motion of the leg upon the thigh ; the ankle-joint has a greater latitude of motion, and the foot may be directed out of the plane of the leg's motion. Atmospheric pressure exercises its influence upon joints. Dr. Arnott estimates the amount of that on the knee-joint at 60 Ibs. ; AVeber of that on the hip-joint at about 26 Ibs. : in the hip-joint of the Megatherium the pressure could not have been less than 150 Ibs. A. Swimming. - - Quadrupeds with inflated lungs are of less specific gravity than water, and swim by alternate extension and flexion of their legs; the effective stroke being the act of extension, when the limb presents a larger area to the water than in flexion : this is seen in the Horse, which strikes the water with the ex- panded and subconcave surface of the hoof, but draws the convex conical part through the water in the bending of the limb pre- paratory to the next effective stroke. In the best water dogs the digits are connected by webs, which are stretched in the back or down-stroke, folded in the return movement. The feet of the Otter are broader, especially the hind ones, and more fully palmated. The Seals and Whales have the limbs fashioned as fins. Man, Avith the chest well expanded, is lighter than water : the presence of mind which counteracts the tendency produced by immersion in a cold and dense medium to expel the air from the lungs is the first safeguard against drowning ; and next, if the art of swimming has not been learnt, to keep the head immersed to the mouth and nose, and to refrain from the misdirected struggles of terror which tend only to hasten on the catastrophe. In swimming, the hands and feet are employed so as to present the greatest surface to the water in the effective stroke, the least in VOL. III. F G6 ANATOMY OF VEKTEBBATES. the preparatory movement ; in this the hands are brought near the mesial plane, with the palmar surfaces parallel to each other ; they arc then thrust forward by the extension of the arm, with the points of the fingers in advance to cut the water with the least resistance ; when the hands have nearly reached their greatest distance from the centre of gravity, they are rotated by pronation, so that the palms are directed at an oblique angle outward and downward ; they are then forced backward by the abduction of the Avhole arm through a large arc of a circle, having the shoulder- joint for its centre, and the length of the arm for its radius ; the fore-arm is then flexed, and carried into its former position pre- paratory to making another stroke. During the extension of the arm, the feet are drawn toward the centre of gravity, with their convex surface directed obliquely backward by the extension of the ankle and flexion of the hip and knee joints, and during the ab- duction of the arm the flat surfaces of the feet are driven forcibly backward and downward by the sudden extension of the leg. From the ratio of the areas of the hands and feet, and the ratio of the difference of their velocities in the two strokes, there results such a preponderance of the force in the vertical direction upward and in the horizontal direction forward as is sufficient to keep the respiratory openings above the surface of the water, and to over- come the resistance which the water opposes to the motion of the body, due to its figure and velocity. B. Moving on J,and. In mammalian quadrupeds the limbs are usually long, and support the trunk horizontally, uplifted from the ground, as on columns expanded at their base. The uppermost long bone is single, the next two form a pair, side by side, and these rest on more numerous ossicles, transferring the weight upon the base of two, three, four, or five diverging piles : the single hoof of the Horse seems an exception, but it, too, ex- pands to its base. The shafts of the long bones are hollow, agreeably with the principle of combining greatest strength with least weight. According to the lightness and speed of the quad- ruped, the limb-bones are inclined to each other's axes at a greater angle. In the colossal Elephant and Megathere they rest on each other almost vertically, in supporting the trunk. The horizontal trunk and produced head and neck of quadrupeds cause the largest proportion of the weight to fall upon the front pair of supporting columns, of which, accordingly, the angles of the joints are less, and the direction more vertical than in the hind pair, as is well exemplified in the hoofed kinds (vol. ii. figs. 307, 309,310). LOCOMOTION OF MAMMALIA. 67 In walking, the Horse, if the right side be in advance, moves first the left hind-leg, second the right fore-leg, third the right hind-leg, fourth the left fore-leg ; propelling the centre of gravity forward over a space equal to the length of the first step. When the left hind-leg is in the act of advancing, the trunk is supported on the other three legs and is balanced on a triangular instead of a parallelogrammical basis. A succession of movements of the four legs, in the above order, constitutes the progression by walking in most quadrupeds ; its rapidity depends on the time occupied in the series of movements by which the limbs effect the step. In a large well-made Horse one foot may move the length of a step in a second of time, when each leg may swing during one quarter and rest on the ground three quarters of a second. Rapid walkers do it in less time, and the interval between putting down one leg and lifting another becomes inappreciable. In quadrupeds with limbs unusually long in proportion to the trunk there is a modifi- cation of the act of walking : the Camel and Giraffe seem to swing along by moving the two right limbs together and alter- nately with the two left limbs. But, though in a quick walk the two legs of the same side seem to be moved forward simul- taneously, and are both off the ground at the same time through the greater part of the step, yet on close inspection the hind-leg is seen to be first lifted from the ground, and after a very brief interval the fore-leg of the same side. 1 In this way of walk the trunk is balanced on a linear basis of support, alternately trans- ferred from one side to the other. In the Giraffe the long neck is then stretched out in a line with the back, giving the animal a stiff and awkward appearance; but this is lost when they commence their graceful undulating amble : 35 the motions of the legs are now peculiar ; the hind-pair are lifted alternately with the fore, and are carried outside of and beyond them by a kind of swinging movement. 2 In the pace of the Horse called the ( trot,' the legs move in pairs diagonally, those marked B, E, fig. 35, e.g. being raised as soon as A, D, strike the ground : the bases of sup- port are alternately in the lines A, D, B, E ; and the undulations from the projection of the trunk are in the vertical, not as when walking 1 xcvir. p. 244. Ib. p. 244. F 2 68 ANATOMY OF VERTEBRATES. in the horizontal, plane. Moreover, in the rapid trot, each leg rests a short time on the ground and swings a longer time. The gallop includes three combinations of movements of the limbs. When the Horse begins the gallop on the right hind-leg, the left one reaches the ground first ; the right hind and left fore- legs next, simultaneously, and the right fore-leg last ; this is termed the gallop of three beats. In the gallop where the four legs strike the ground successively, the left hind-foot reaches the ground first, the right hind-foot second, the left fore-foot third, and the right fore-foot fourth ; this is the ( canter,' or gallop of four beats, but it is not the kind of movement adapted for great speed. The gallop wherein the legs follow the same order as in the trot that is, the left hind and right fore-feet reaching the ground simul- taneously, then the right hind and left fore-feet is the order in which horses move their feet in racing, where the greatest speed is required, and is called the gallop of two beats. In the ' amble,' the two legs on one side rest on the ground and propel the centre of gravity forward, whilst those 011 the opposite side are raised and advanced, and, on taking a new position on the plane of motion, the former pair are raised and advanced in a similar manner : these successive actions are accompanied by considerable lateral motion. This resembles the gallop of the Giraffe, and is a result of special training in the Horse. In the ordinary gallop, the centre of gravity moves in a vertical plane, and describes the path of a projectile. The space passed over on the plane of motion is equal to the horizontal velocity of the centre of gravity multiplied by the time. According to Sambell, the horse Eclipse, when galloping at liberty and with its greatest speed, passed over the space of twenty-five feet at each stride or leap, which he repeated 2J times in a second, being nearly four miles in six minutes and two seconds. Flying Childers was computed to have passed over eighty-two feet and a half in a second, or nearly a mile in a minute. In both these famous racers the muscular system had been allowed to gain its full developement, as at four years, before being exercised for the course : modern impatience strains and spoils the muscles by the chief prizes being allotted to three-year-old horses. In many Marsupials and Rodents the hind-legs are shorter than the fore-legs, the disproportion being greatest in the Kan- garoos and Jerboas. In slow progression the Kangaroo supports the body on the tail and fore-legs, while the hind-legs are simul- taneously moved forward outside and in advance of the fore-legs ; the base of support being here transferred from a triangle to a transverse line. In full speed the tail is rigidly outstretched to LOCOMOTION OF MAMMALIA. 69 afford a firm fulcrum to muscles passing from the caudal vertebrae to the pelvis and hind-limbs : the short fore-limbs are tucked up to the chest so as to offer the smallest surface to the air, and the animal progresses in a series of bounds by simultaneous move- ments of the hind-limbs. The Rabbit, in moving slowly, advances the fore-feet two or C5 / 3 three steps alternately. The body being thus elongated, the hind- legs are suddenly extended and drawn forward simultaneously : it thus, as it were, walks Avith the fore-legs, and leaps with the hind. The Hare is under disadvantage with its long hind-limbs in running down-hill, owing to the great inclination of the axis of the trunk to the plane of motion, and it usually zigzags as it descends ; but it gains proportionally in the ascent, and its speed on level ground, through the size and strength of the chief pro- pelling limbs, is very great. The degree of flexion of the trunk accompanying the movements of these and other quadrupeds is indicated by that in which the neural spines converge toward the single vertical one marking the centre of motion, and it is commonly greatest in the unguiculate quadrupeds. The vertically of the long and narrow tarsus and metatarsus producing the f digitigrade ' character of the type Carnivora, com- bines with the geometrical and physical relations of the other parts of the limbs to give them their superior speed and agility. In the Dogs and Cats the oblique scapula, being unfettered by bony (clavicular) connection with the sternum, enjoys the freedom of rotation which characterises it in the swift Ungulates. The humerus in the Lion (vol. ii. fig. 337) has its axis directed down- ward and backward, forming with that of the scapula an angle of 110. The olecranon projects so far behind the axis of rotation in the elbow-joint as to constitute a powerful lever for the exten- sors of the fore-arm. The hind-limbs are longest, and the bones o are inclined more obliquely to each other than in the fore-limbs, subserviently to elasticity and power in springing. The calca- neum is produced on the same principle as the olecranon, but forms the more powerful lever of the two. The last perfection is given to the limbs of Carnivora by the modifications of the toes of Felines, whereby their tread is noiseless, and the claws exempt from the wear and tear of progressive motion. It is effected by a joint allowing the ungual phalanges to be brought in extension above the middle phalanges, elastic ligaments being adjusted to keep the joint so extended, and by a thick cushion of soft elastic substance beneath the joint or parts of the phalanges transmitting the superincumbent weight to the ground. 70 ANATOMY OF VERTEBRATES. In the toes of the fore-foot the last phalanx is retracted on the ulnar side of the second phalanx. The principal elastic ligament arises from the outer side and distal end of the second phalanx, and is inserted into the upper angle of the last phalanx : a second arises from the outer side and proximal end of the second phalanx, and passes obliquely to be inserted at the inner side of the base of the last phalanx : a third arises from the inner side and proximal end of the second phalanx, and is inserted at the same point as the preceding. The tendon of the s flexor profundus 36 perforans' is the antagonist of these ligaments. The toes of the hind-foot are retracted in a different direction, viz. directly upon, and not by the side of, the second phalanx ; and the elastic ligaments are differently disposed. They are two in number, arise from the sides of the second phalanx, and converge to Elastic ligaments of Liou-s daw. ^e inserted at the superior angle of the last phalanx. In fig. 36, a is the pair of elastic ligaments ; b, the tendon which pulls out and works the claw; c, inelastic ligament continued from the 6 extensor ' tendon, which is mainly inserted into the second phalanx. 1 The main purport of the modifications of the motory system in Quadrumana is to make them climbers. By the developement and direction of the hallux the hind-foot is converted into a hand, with unusual power of prehension, especially in the Gorilla ; the joint of this hand is so modified as to give it a free motion excentric to the axis of the leg, whereby its outer edge is applied to the ground ; the whole hind-limb is shortened, disproportion- ately so in the best climbers (vol. ii. fig. 180), in which also the hind-limb may be unfettered, for its acts of manipulation, by the absence of the ( ligamentum teres ' of the hip-joint (Pithecus). The length of the iliac bones relates to elongation of the muscles for rotating the hind-limb and hand more quickly and through greater spaces. Correlatively, the scapular arch approximates to the condition of the pelvic one by the extension of complete clavicles to the manubrium, and the head of the humerus is re- ceived into a deeper and more secure socket than in Bimana. This is well exemplified in the long-armed Gibbons, which enjoy the peculiar mode of locomotion called ' brachiation.' The body is set into pendulous vibration by the action and reaction of the 1 The dissections of the Lion's foot showing the above-tlescrihed modiiications of the elastic ligaments are Nos. 287A and 288A, Physiol. Series, vol. i. xx. LOCOMOTION OF MAMMALIA. 71 muscles of one arm and of the trunk, the force finally attained and the swing being such as to propel the animal some distance through the air ; a bough is seized by the opposite out-stretched arm, and the momentum is applied in aid of a repetition of the action to gain a longer launch. I have myself witnessed, in the London Zoological Gardens, an aerial leap of upwards of fifteen feet so effected by the long arms of a captive Hylobat. M. Duvaucel, observing them in their native forests, testifies to their passing through a distance of forty feet from bough to bough. Mr. Martin, when curator of the Zoological Society's Museum, watching the same female Hylobates agilis which had been the .subject of my own study of the brachiating mode of motion, states that, ( a live bird being set at liberty in her pre- sence, she marked its night, made a long swing to a distant branch, caught the bird with one hand in her passage, and at- tained the branch with her other hand, her aim both at the bird and the branch being as successful as if one object only had gained her attention.' * In most of the Platyrhine monkeys the tail is prehensile, and becomes, in Ateles more especially, a fifth independent organ of grasping. In ordinary progression on the ground the Quadrumana move as quadrupeds ; but the higher tailless Catarrhines (Apes), in- stead of setting the palm or outer margin of the fore-hands, like the inferior families, to the ground, apply the back of the second phalanges of the flexed fingers, the skin covering which has a broad and thick callosity, whence these apes are sometimes called collectively, f knuckle-walkers.' The longer-armed kinds, in slow movement, support the body upon the knuckles, as upon a pair of crutches, and swing the hind-limbs forward between them. In more rapid movement they sway the trunk and hind-limbs in a sort of sidelong sweep, progressing by a kind of shambling amble. The tracks of the Gorilla show this to be o the habitual mode of progression along the ground. 2 Station or motion on the lower limbs only is shown to be difficult by its awkwardness and the shortness of time during which it can be maintained. The walk is a waddle from side to side, the huge superincumbent body being balanced by swinging movements of the long arms, or by clasping the hands behind the head. When so pursued as to be driven to stand at bay, the Gorilla, like the plantigrade Bear, raises himself on the hind-hands, so as to have his powerful arms and fists free for the combat. 1 XLVIII". - xili". p. 532. 72 ANATOMY OF VERTEBRATES. 37 The Bimana are as expressly adapted to station and movement on the ground as are the Quadru- inana to climbing in the forest. There is no known connecting link between the lowest variety of Man and the highest species of Ape. No animal is served by arms, at once so large and variously flexible and applica- ble as Man ; in none are the termi- nal divisions of the limb so distinct in their power and adaptability. 1 The mechanism of the vertebral column and limbs which makes Man a f plantigrade biped,' and the only one in the Animal Kingdom, is as perfect in the Mincopie, 2 Australian, or Boschisman, as in the most advanced member of the white race. The locomotive frame of any variety would equally serve as the subject of such elaborate analyses of the mechanical condi- tions of ( standing,' ' walking,' ' run- ning,' ( leaping,' &c. as have been given by Borelli, 3 Barthez, 4 Rou- lin, 5 Gerdy, 6 and W. & E. Weber, 7 to whose works, and especially the latter, the reader is referred for this interesting branch of Animal Mechanics. LX1V. 4 XIV. - XXXVII". XV. 6 XVI". 3 cxxxr 7 XII". Figure 37 exemplifies a Man stooping with a load, and sustained in that position by the glutei, f, the quadriceps feraoris, y, and the gastrocnemii, /. If the weight r be 120 Ibs., that of the bearer 150 Ibs., and if the line r s be the direction of the force of gravity cutting the femur and tibia in c and x, the centre of gravity of the Man being at b, and the common centre of gravity of the Man and his load at a, then the weight of the Man from the head to b will be = 'I Ibs. = 75 Ibs., and that of the section b to c, by supposition, = 47 ; therefore the weight of the arc a b c = 75 + 47 = 122, also by supposition the section c v x = 20, and consequently the whole arc a b v x 142 ; the distances of the directions of the muscles from the axes of the joints to the distances of the line of gravity arc, according to Borelli, in the following ratio, ^ the distance/ b is to the distance m b as 1 is to 8 ; ^ o v is to t v as 1 to 6 ; \ k d is to p d as 1 to 3 ; and t v to b m as 3 to 4 ; hence he derived certain proportions, from which he estimated that the extensor muscles of the leg, to sustain this weight, exerted a force = 6032 Ibs., being more then fifty times the weight. MYELON IN MAMMALIA. CHAPTER XXVIII. NERVOUS SYSTEM OF MAMMALIA. 203. Myelon. - The myelon in Mammals, as in Birds, quits, in the course of develope- meiit, the hinder part of the neural canal, mov- ing and concentrating forwards, and leavino- *- J o ' O the concomitaiitly elongated roots of the nerves, between their places of exit at the intervertebral foramina and their places of attachment to the myelon, as an indication of the primitive extent of the nervous axis. It is remarkable that the Monotrematous order, so restricted in its representative genera, should present the two extremes of this deve- Ippemental difference in the length of the myelon. The Ornithorhynchus hardly departs from the condition of the lizard, the myelon extending into the sacrum, and having the intravertebral nerve-roots limited to the short canal of the caudal region ; whilst in the Echid- na, fig. 38, the myelon moves forward to the middle of the dorsal region, d, where it ends in a point, and leaves all the canal behind occupied by the elongated nerve-roots and shrunken emptied myelonal sheath, answering to the ' caucla ecjuina ' and ( filum terminale ' of anthropotomy, but of extraordinary length. In the Ornithorhynchus the myelon fills closely the neural canal : it is thickest at its commencement and at the lower two-thirds of the cervical region ; it is more slender in the back, especially near the loins ; it is slightly enlarged in the lumbar region, and gradually terminates in a point at the end of the sacral canal. The short and thick myelon of the Echidna presents the two usual enlarge- Brain and spinal chord, Echidna, half nat. size. 74 ANATOMY OF VERTEBIIATES. 39 merits, giving origins respectively to the nerves of the pectoral mid pelvic extremities, the slightly contracted intermediate por- tion being extremely short. In the Marsupialia the myelon usually extends to the sacrum, and presents both brachial and pel- vic enlargements which correspond with the relative size and muscu- larity of the extremities to which they furnish the nerves ; the latter enlargement is consequently most marked in the Kangaroo, fig. 39, but does not exhibit the rhomboid al sinus of this part in Birds. The disposition of the layer of grey matter enveloping the central me- dullary tract in each lateral moiety of the chord is shown in the three situations marked i, 2, and 3 ; the superior expansion and com- plexity of the grey matter in the anterior columns of the pelvic en- largement, 3, accords with the pre- dominance of the locomotive over the sensory functions in the long and strong saltatory legs of the Kangaroo. In the Lissencephala we have again examples of the concentra- tive protraction of the myelon into the dorsal region, as e.g. in some Cheiroptera and in the Hedgehog. From the coincidence of the condition of the myelon with the tegumentary covering in Erinaceus and Echidna, we are led to ask, whether the shortness of the solid chord, and the great length of the suc- ceeding nerves within the neural canal, have any physiological relation with the habit, common to both the placental and mono- trematous hedgehogs, of rolling the body into a ball when torpid or asleep, or when the tegumentary armour is employed in self- defence. In the bat it would seem to be concomitant with the reduced size and function of the pelvic limbs : but, in the Noctules ( Vespertilio noctula), the myelon extends to the lumbar vertebra. The anterior enlargement is the chief one in Cheiroptera, and is close Myelencephalon, Macropus. MYELON IN MAMMALIA. 75 to the medulla oblongata, as it is likewise in the Cetacea. In most Rodentia the myelon terminates in the lumbar region, but in the rabbit it extends a little way into the sacrum. In the mouse the relative proportion of the myelon to the brain is as 22 to 100. In the Cetacea and Sirenia, the myelon presents only the anterior enlargement, which is very near the brain, and is remark- able for the close aggregation of the origins of the nerves from that part. The myelon is closely invested by the dura mater, which is directly perforated by the nerves, and the sheath terminates at the pointed end of the myelon, not being continued as such, over the c cauda equina.' The myelon is small in proportion to the size of the body, shows the central canal, and, Hunter remarks, ' is more fibrous than in other animals ; when an attempt is made to break it longitudinally, it tears with a fibrous ap- pearance, but transversely it breaks irregularly.' * In the Elephant the dura mater surrounds the myelon less closely than in the Cetacea, and the roots of the nerves have a longer course within the sheath. In the Giraffe 2 I found the myelon closely invested by the dura mater, which was thinner on the dorsal than on the ventral side : it is chiefly remarkable for the length of the cervical portion, which from the corpora pyra- midalia to the pectoral or brachial enlargement measured four feet three inches. The elongation of this part during foetal de- velopement proceeding by uniform interstitial addition, the roots of the nerves become equally separated from each other ; and, as the lowest filament of one root was not further removed from the hio-hest of the next below, than this from the succeedino; filament O J CD of the same root, such filaments were extended over an unusual space of the myelon ; the root of the third cervical coming from a tract of not less than six inches in length : the contrast between the cervical myelon of the Porpoise and Giraffe in this respect is striking. o With the singular exceptions of the Echidna, Hedgehog, and certain bats, the mass of the myelon bears a direct ratio to that of the body throughout the Mammalian series, and its structure is essentially the same. In the adult human male it a little exceeds an ounce in weight ; its tissue is firmer than that of the O brain. As in all Vertebrates, the ventral and dorsal surfaces are respectively divided into equal moieties by a longitudinal fissure, of which the dorsal is deepest, and, in the Mammalia, closest. In Man, the interfissural plate of pia mater can be shown to be a fold in the ventral (anterior) fissure, fig. 40, a, but is confluent as a 1 xciv. p. 374. 2 xcvn'. 76 ANATOMY OF VERTEBRATES. single delicate layer of vascular tissue in the dorsal (posterior) one, ib. c. A layer of white iieurine accompanies the ventral fold, which, when withdrawn, shows the fissure to be closed by such layer, perforated by numerous holes for capillaries : its fibres are trans- verse and form the ( white myelonal commissure.' The depth of the ventral fissure is greatest at the pectoral enlargement of the myelon, and gradually diminishes towards the ' cauda equina.' The deeper dorsal fissure penetrates fully one-half of the dorso- ventral diameter of the myelon through the greater part of its course, but becomes shallower in the lumbar region : it is bounded by a layer of grey neurine, connecting the same tissue in each lateral moiety of the myelon,, which layer forms the ( grey mye- lonal commissure.' In the developemeiit of the myelon, as of the encephalon, the central part contains a fluid which is reduced by the endogenous grow 7 th of neurine, on ap- proaching maturity ; it re- mains in the myelon, as its e canal,' which is obvious in the cold-blooded Verte- brates, 1 and is exposed, in birds, as the ' ventricle of the pelvic enlargement,' as it is in the ' fourth ventricle ' of all Vertebrates, where it bears the name of ' calamus scriptorius ' in anthropoto- my. The myelonal canal is more obvious in lower mam- ancl fourth cervical nerves. Magnified ten diameters- mals 2 than in Man, aild in Z Transverse section of the human myelon, close to the third XVIII". the foetus than in the adult ; in whom, whilst unobliterated, it is surrounded, like the more obvious myelonal canal in Reptiles, by the grey commissural neurine. The canal is lined by ciliate cells. 3 The lateral columns of this tissue, united by the commissure, are thicker but less peri- pherally extended in the ventral, y, than in the dorsal, h, portions of the myelon. In transverse section the grey neurine resem- bles a comma, the concavity of which is directed outward, the head, fig. 40, g, is surrounded by the peripheral white neurine, and the tail, ib. h, i, is produced to the issue of the dorsal (posterior) nerve-roots, ib. k. The proportions of the grey and 1 vol. i. pp. 272, 296. 2 xx. vol. iii. p. 43, no. 1362. 3 xvni". MYELON IN MAMMALIA. 77 white neurine vary in different parts of the myelon. In fig. 41, i is a section at the fore (upper) part of the pectoral enlargement, the head of the comma is small, the tail narrow : in the middle of the enlargement, section 2. the head is larger, . * i with more distinct processes, the tail is thicker. In the dorsal region, sections 3, the grey matter is more reduced than in the neck. In the lum- bar region, sections 4, it again expands, the head shows the stellar character, is fenced off from the ventral periphery by a smaller extent of white neurine ; the tail is thicker, but here becomes shorter and seems not to reach the dorsal surface. Near the termination of the myelon the comma-shape is lost, and the grey neurine reduced to a subcylindrical tract, slightly notched laterally and surrounded, save at the commissure, by the white neurine. Of this tissue the largest proportion exists in the cervical part of the myelon and its enlarge- ment, where the small columns called ( posterior pyramids ' are continued from the dorsal part of the medulla oblongata, contracting to a point, near the end of the brachial enlargements, and there allowing the proper dorsal (posterior) columns of the myelon to come into contact at the posterior fissure. The difference in the proportions of white and grey neurine in the ventral and dorsal tracts of the myelon coin- cides with the different nervous endowments of the pectoral and pelvic limbs : in the former volition and sensation are greatest ; in the latter reflex actions with diminished sensibility : the exercise of the arms and hands induces more calls upon cerebral action, that of the legs and feet operates more exclusively through physical changes of the lumbar part of the mye- lon itself: hence, therefore, the need of a greater proportion of the reproductive or grey tissue. Numerous multi-caudate vesicles are present in the grey neurine, and linear tracts are continued from the major part of its periphery, as seen in transverse section, towards that of the myelon, accompanied by capillary vessels which enter the pia mater. The proportion of the neural canal to the myelon varies in Transverse sections of the human Myelon. A. Anterior or ' ve ntra\. P. Posterior or ' dorsal.' 78 ANATOMY OF VERTEBRATES. different mammals: it is greatest in the Cetacea, Sirenia and Seal-tribe, the space between the myelon and neural arches being occupied by blood vessels, which, in those aquatic orders, are chiefly arterial plexuses. In land-mammals and Man the veins pre- Communication of the ' perineurar sinus with the veins of vertebral centrum, vii". Transverse section of dorsal vertebra and contents of its neural canal, xix". dominate, having more or less of the character of sinuses, as shown in the section of the lumbar vertebra, fig. 42, where the communi- cation of the f perineural ' veins, d, with those of the tissue of the vertebral centrum, is shown. But the most constant fluid exter- nal to the myelon is that which has been called 6 cerebro-spinal.' In the dorsal region of the neural canal, in Man, the position of this fluid is shown in fig. 43, where c is the myelon, with its pia mater and arachnoid, in the dorsal or posterior septum, n the nerve-roots, and s s the sub- or ent-arachnoid space. The use of the uniform support and defence afforded by the interposition of this fluid between the myelon and the hard walls of the neural canal is obvious. 1 The arachnoid is disposed about the myelon, as about the brain, after the manner of the serous membranes ; it consists of an exterior or ( parietal layer ' reflected upon the myelon to form the internal or ( myelonal ' layer. If a section be made through a pair of nerve-roots, those e.g. of the fifth cervical, fig. 44, the arachnoid is seen to be continued as a loose sheath, about the inter-neural part of the root, n n, and is reflected so as to form small culs-de-sac, at the orifices of emero-eiice. O In Man the myelon is loosely invested by the ' dura mater,' to which it is attached by In which (he effects of the removal of this fluid in the Dog are described. 44 Transverse section of the myelon and its membranes across the roots of the fifth cervical nerves. 1 XIX". ENCEPHALON IN MAMMALIA. 79 46 processes of the arachnoid called f ligamentum denticulatum,' and the nerve-roots. 204. Encephalon, its primary divisions. The encephalon, or brain, of Mammals, like that of lower Vertebrates, Tur- tle, fig. 45 (vol. i., Shark, fig. 187, and Lepidosiren, fig. 186), presents four primary Se "- Brain of a Turtle (Chelone), side view. merits or divisions, indicated by as many superincumbent, origi- nally vesicular, masses, or pairs of masses ; but consisting, not only of those, but of tracts of the myelencephalic columns from which those masses are successively developed. The hindmost division, or 6 epencephalon,' fig. 46, c, con- sists of the enlarging parts of the myelencephalic columns, a, called f medulla oblongata,' of the superincumbent mass, c, originally a pair in the human foetus (fig. 47, c), called ( cere- bellum,' and of a transverse commissure of that body, called 6 tuber annulare ' or ( pons varolii,' p ; the three parts, so named in anthropotomy, are subordinate elements of one and the same pri- mary division of the encephalon. 1 The next division includes the parts of the myelencephalic columns which support, and from which are developed, the optic lobes, o : it is the 'mesen- cephalon,' figs. 45, 46 and 47, o. With the columnar elements v j^^^/ K are the parts Called the ( fillet,' Brain of human foetus, at four months, side view. and ' processus a cerebello ad testes ' in anthropotomy, including the 6 third ventricle ' and its prolongations into the vascular appendages 1 The severance of the 'pons,' and raising it, in association with parts of another segment, to the rank of a distinct primary division as ' mesocephalon,' and the sever- ance of the ' medulla oblongata' from the cerebellum, as a co-equal division, called ' metencephalon,' indicate the warping of the judgment through habitual contem- plation of the characteristically modified and developed parts of the human brain. P Brain of Opossum > side view. 80 ANATOMY OF VERTEBRATES. called ( pineal ' and ( pituitary ' h, glands : a second pair of gangli- onic masses are developed in Mammalia behind the optic lobes, o, and received from the old anthropotomists the name of ( testes,' the more constant and important pair being the f nates,' and the whole, from their arrested condition in Man, forming the ' corpora ( quadrigemina ' or ( bigemina.' The third primary division of the brain includes the ( crura cerebri ' with the reinforcing or recruiting ganglions called ( thalami optici ' and ' corpora striata,' and the superincumbent masses called ( cerebral hemispheres : ' it is the e prosencephalon,' figs. 46 and 47, P. The foremost primary division of the brain includes the anterior termination of the columnar tracts, called ' crura rhinencephali,' and the appended vesicular mass, called ( olfactory lobe ; ' it is the 6 rhinencephalon,' ib. R. The nature and value of this division are masked, in Man, by the arrest of its developement and the contrast of the excessive expansion of the vesicular part of the antecedent division. Accordingly the ( crura rhinencephali ' are termed ( olfactory nerve ' with its ( roots,' and the primary vesicle is the ' bulb of the olfactory nerve,' of anthropotomy. Each primary encephalic division has its cavity or cavities called ' ventricles.' The epencephalic prolongation of the mye- lonal canal is the ( fourth ventricle :' its continuation into the primary vesicle is the ( cerebellar ventricle :' it is persistent in fishes (vol. i. p. 275, fig. 178, c\ reptiles (ib. p. 295, fig. 193), and birds (vol. ii. p. 120, fig, 45), but is obliterated in Mammals where the cerebellum is solid. The ' myelonal canal ' passes for- ward as the ' third ventricle,' and ' iter ' or communicating canal between that and the ' fourth.' Its continuation into the optic lobes, retained in oviparous Vertebrates (vol. i. p. 278, fig. 182, h, b, p. 279, fig. 183, d, p. 295, fig. 193, 3, vol. ii. p. 120, fig. 45, o,) is obliterated by growth of neurine in Mammals ; as is also its ascending canal to the ' pineal appendage ; ' the descending one to the ( hypophysis ' is retained as the ' infundibulum.' Each cerebral hemisphere begins in Mammals, as in lower Vertebrates, as a bladder with a thin wall of brain-substance, the cavity including, potentially, all the anthropotomical 'horns,' ' fore,' 6 aft,' and 'under,' of the 'lateral ventricle,' which are subsequently meted out by endogenous growths of grey and white neurine, in size and shape according to the group or genus. In most Mammals which derive so important a share of their ideas through the olfactory sense, the ' lateral ventricle ' is con- MACROMYELON OF MAMMALIA. 81 tinned into the ' rhinencephalon,' as shown in fig. 46, d. So that all the essential parts of a primary encephalic division, viz. the columnar as ( cms rhinencephali,' the superimposed mass, and the cavity exemplifying the nature of the olfactory bulb as a c primary vesicle ' of the brain, are present. 205. Macromyelon.- -The epencephalon consists of the ma- cromyelon and cerebellum. The term ( macromyelon ' is not exactly the equivalent of the ( medulla oblongata ' of anthropo- tomy, the authorities in that department of anatomy having ap- plied the phrase in different senses. With Willis, 1 it included the part of the brain beneath the cerebellum and cerebral hemispheres, * all that substance,' e.g., which reaches from the cavity of the callous body and conjuncture in the basis of the head to the hole at the hinder part where the same substance, being further con- tinued, ends in the f spinal marrow.' With Vieussens, 2 the ( oblong marrow ' included the columns of the neural axis between the 4 spinal marrow ' and the ' cerebral hemispheres,' with the ( crura cerebri ' and their ganglionic enlargements, called ' optic thalami,' and ' corpora striata.' Winslow 3 defines the ' medulla oblongata ' as the medullary basis common to both cerebrum and cerebellum. Haller 4 restricts the 'medulla oblongata' to the intracranial myelonal columns, as far as the ( pons varolii.' Rolando 5 prefers the older view of its extent. Chaussier, 6 ao*ain, distinguishes 7 O O the portions of the intracranial columns crossed by the transverse commissural fibres of the cerebellum as a primary division of the brain, under the name ' mesocephale ; ' and this term has been extended by Todd 7 to include the f corpora quadrigemina ' with the f processus cerebelli ad testes,' and part of the floor of the fourth ventricle. But the developement of the human brain and its several stages, represented by the conditions at which it is arrested in lower vertebrates, show that the transverse commissural fibres which cross or decussate with the intracranial myelonal columns, whether under the name of ' pons,' or ( trapezoid bodies,' or ' arciform fibres,' are subordinate adjuncts to other parts, chiefly the cere- bellum ; while the distinct and superimposed masses called ( cor- pora quadrigemina ' include the true correlatives of the cerebrum and cerebellum, as primary vesicles of the brain. By ( macromyelon,' therefore, I signify the intracranial prolon- gations of the myelonal columns as far forward as their emergence from the ' pons,' or cerebellar commissure : in this tract they are 1 xxi". p. 5. 2 xxir'. 3 xxiii". 4 xxnii". 3 i.". 6 xxvi". r xxvii". p. 084. VOL. III. G 8-2 ANATOMY OF VERTEBRATES. 48 reinforced by masses of grey neurine, and the transverse commis- sural fibres are so intermixed with the longitudinal ones as to compel their being combined in description as in delineation, figs. 48, 56. But, before quitting the Mammalian class, the reduction of the * pons,' concomitaiitly with that of the side-lobes of the cerebellum, as in figs. 51 and 53, is such as significantly to testify against its title to be regarded as a primary division of the brain ; and in birds a ' tuber annulare ' or ( pons varolii,' ceases to appear upon the under surface of the myelencephalous tract above defined. From this tract the cerebral nerves, from the fifth to the hypoglossal or ninth inclusive, arise. In advancing to the formation of the macromyelon growing central tracts of the myelonal columns come to the peri- phery, and push aside the medial tracts on both the ventral and dorsal surfaces. On the former, fig. 48, they decussate, as they appear, at d, and, with a con- tiguous portion of the anterior myelonal columns, b, expand to form the s prepyramidal bodies,' p. The rest of the anterior columns, b, with the contiguous antero-lateral co- lumn, in their course along the macromyelon, are associated with a mass of grey matter oc- casioning a swelling out of the surface, called the ( olivary bodies,' ib. o. A thin layer of superficial fibres which, in lower Mammals with non-prominent ( olives ' pass outward, as a ' trapezoid layer,' in Man curve round the exterior of the olivary prominences, and constitute the ' arci- form fibres,' ib. A. The transverse fibres defining anteriorly the f prepyramids ' and c olives ' increase in mass, from the lowest Mammals ( Orni- tliorhynchus, fig. 51, c, Didelphys, fig. 53, b), to Man, fig. 48, a. As they arch over the fore part of those macromyelonal tracts they have been called ' pons ;' but their true position is that of an inverted or suspended bridge : their developement is in the ratio of that of the side-lobes of the cerebellum. On the posterior or dorsal surface of the myelon the deep- Macrcmiyelon, anterior or ventral aspect. Man, nat. size. MACROMYELON OF MAMMALIA. 83 49 X Macromyelon, posterior or dorsal aspect, with section of cerebellum. Infant, nat. size. seated tracts become superficial at a greater distance from the skull than on the ventral surface, and do not decussate ; they ex- pand as they enter the macromyelon, and form the ' post-pyra- midal bodies,' fig. 49, Y. The posterior myelonal columns which thev / push aside, diverge as they are continued into the macromyelon, and combine with the con- tiguous lateral columns to form the post-resti- form tracts, x. In ad- vance of the post- pyramids, still deeper columns of the myelon come into view, as the ' teretial tracts,' ib. A, F, bounding the sides of the fissure, called 'calamus scriptorius,' at the floor of the expanded macro - myelonal canal called f fourth ventricle.' This is over-arched by the cerebellum, here bisected, and one half reflected at R ; the pe'duncle or ' crus ' of the opposite half being shown at u. The thin layer roofing the ventricle anterior to the crus is called ( valve of Vieussens,' B. Sections of the macromyelon, as at fig. 50, show the form of the grey matter, called ' corpus dentatum,' of the olives, o o, and the relative position of the en- larging columns. Those on each side the fissure A, are the prepyramids ; those on each side the fissure P, are the post-pyramids ; the lateral or restiform tracts intervene between them and the olivary tracts, o. In the Monotremes the macromyelon is large in proportion to the rest of the brain, but the ' pons ' bears relation to the cerebellum in its smallness. The prepyramids, figs. 51 and 52, , are long, narrow, flat, and contract as they Transverse sections of 1,1 n i i the macromyelon, at the approach the pons, especially in the Ormtho- parts marked x and Y i i ,1 i r> r -i r> /* s\ ? fig. 49. Man, nat. size rhyncnus; the olives, fig. 51, , fig. 52, b, are also long and flat, but expand as they approach the pons, and are crossed, before reaching it, by the ' trapezoid ' homologues of the ( arciform ' fibres in Man. The distinction between the olivary and pre-restiform tracts is less marked. The grey matter G 2 84 ANATOMY OF VERTEBRATES. is small in the olivary tracts, and does not form a 'corpus denta- (11111." The pons is Hat, it forms a narrow transverse band in the Side view and base of brain, Ornithorliynchus. Base of brain, Echidna. 53 Ornithorliynchus, fig. 51, c ; these fibres cover a greater antero- posterior extent of the macromyelon in the Echidna, and give the pons a triangular form. In the Opossum the pons, fig. 53, b, is reduced almost to the proportions of that in the Ornithorliynchus ; the prepyramidal, d, and olivary tracts are similar, and the latter are crossed by as well- marked a trapezoid arrangement of trans- verse fibres, c. The prepyramidal tracts come to the sur- face at a greater distance from the pons, in most Mammals, than in Man, and thus resemble more the postpyramidal tracts ; this character is shown in the Horse, fig. 54, Dolphin, fig. 60, b, and Baboon, fig. 62. In the anthropoid Apes, the proportions of the prepyramids (fig. 112, Orang) approach those in Man, and the arciform disposition of the superficial layer of crossing fibres begins to prevail, and to allow the olives, which are likewise here more prominent, to come into view. Although the olives are less prominent in Delphinus than in the Apes, they are equally uncovered by the trapezoid fibres : and show internally the arrangement B:ise of brain, Didelpliys. MACEOMYELON OF MAMMALIA. 85 of grey matter called ( corpus dentatum.' The pons, fig. 60, 5, c, by its prominence and antero-posterior extent, corresponds with the great lateral developement of the cerebellum, e. When the prepyramids, fig. 55, /?, are divaricated in the human macromyelon, the median fissure, which is wider and shallower than 55 al Base of the Brain, Postpontal part of Macromyelon, anterior or ventral aspect. Man, xxxiti". that, c, below the decussation, shows the same cribriform cha- racter of its f floor,' formed by the penetrating vessels from the fold of pia mater which lined it. A further extent of divarication shows transverse fibres uniting the halves of this part of the macromyelon, and decussating with longitudinal fibres, as in fig. 56. The section of the prepyramid on each side of a, fig. 57, shows its triangular figure and the restriction of grey matter to the ' nuclei,' /*, s ; they are mainly composed of white longi- tudinal fibres which enter the pons above its lower or peripheral transverse fibres, and interlace with the fibres of a higher plane : at the entry each pyramid is constricted, as at fig. 56, p, but soon expands. The proportion of the decussating and non-decussating tracts of the prepyramidal columns is shown in fig. 56, where p is part of the right prepyramid cut across near the pons and reflected to show the decussating fasciculus, d, and the non-decus- sating fasciculus, n, continued through the pons, P: the decus- 86 ANATOMY OF VERTEBRATES. sating fasciculus of the left prepyramid is shown at d f . The fibres of the outer white neurine of the olives are longitudinal, and are continued forward above the pens, as shown at f, fig. 66. The nucleus of grey matter sinks deep into the macromyelon, as shown in the sections, figs. 50, o and 57, y ; its section in any direction presents the undulated course of the white capsule suggesting the anthropotomical term 4 corpus dentatum.' The lateral or restiform columns, diverging, as in fig. 49, x, are mainly continued into the cerebellum, of which they form the hinder or f in- ferior peduncle,' fig. 66, r. Recruit- ing grey neurine is developed in their interior. The post-pyramidal columns, contracting as they diverge and ascend, are closely applied to the restiform tracts, but are continued, as the ( fasciculi graciles,' into the crura cerebri. Stilling l has enriched anatomy following magnified view Dissection of macromyelon, seen obUaiiely from the right side. Man, xxxiii". of a transverse section of the macromyelon, one half of which shows the structures as seen by transmitted light, fig. 57. The anterior or ventral fissure, , is here seen to be much deeper than the opposite one, b, represented by the ( calamus scriptorius.' The septum or raphe, c, of the lateral moieties is a compact white neurine ; d, v, are the prepyramidal columns, of which r is the large nucleus, s s the smaller nuclei ; the roots of the hypo- glossal nerve, /, run along the interspace between the pyramids and olives. Of the latter the nucleus is shown at g^ with its plicated capsule of white neurine ; a small mass of grey substance is situated near the olivary one at u ; x indicates grey matter and % gelatinous matter, near the roots of the vagal nerves, k k. The nucleus of the vagus is h, with the root of which nerve is also connected the white longitudinal fibres, m. Whether g be ex- clusively related to the hypoglossal, or is the place of origin (part of the larger root) of the trigeminal, is undetermined ; n is the f soft column,' o the wedge-like column ; f is the nucleus of the restiform body. The transverse or arciform fibres covering this 1 XVIll". MACROMYELON OF MAMMALIA. 87 w. lateral column are marked p, those continued over the olives, and those over the prepyramids, v ; they form the trapezium in lower Mammals. The nucleus in the trapezium, on each side of the raphe, so closely resembles, at a higher section, the olivary body, that it has 57 \v Transverse section of the macromyelon through the lower third of the olivary hodies. Magnified tea diameter*. been termed the ' upper olive ' ; it makes its appearance near where the lower olives first diminish in size. In the Sheep it appears as a group of large stellate multipolar cells, and these cells are more numerous in the Rodents, and still more so in the Cat. In the Rabbit the upper olivary body is convoluted in three or four turns ; in the Mouse it consists of a wavy mass of large and numerous cells ; its structure is especially distinct in the Cat. The f post-pyramidal ' and ( restiform ' nuclei are present in all Mammals. The olivary bodies consist of lavers of small cells / / penetrated by the arciform filaments, by which they are connected with each other and with the raphe ; they are not absent in the Sheep. The transverse section of the human medulla oblongata in the region of the first cervical nerve is more circular, less 88 ANATOMY OF VERTEBRATES. elliptical, than in the Sheep and most lower Mammals. The restiform and postpyramidal nuclei are relatively larger, but the Quad nim ana and Caruivora approach the human structure in this particular; the Cat, e.g., shows an intermediate condition be- tween those in Ruminantia and Bimana. 1 In comparing the macromyelon of the Mammal (fig. 50) and Fish (vol. i. fig. 172) the usual course of structural differentiation seems to be reversed ; a greater number of longitudinal tracts are definable in that of the Sturgeon or Shark than in that of Man. But the superior character is more seeming than real ; the super- addition of ascending fibres in the higher Vertebrate tends to obliterate the boundary lines and seems to blend tracts the i funicular ' and post-pyramidal, e. g. in the Mammal, which are distinguishable in the Fish. 206. Cerebellum. The posterior and restiform columns, pushed aside by the postpyramidal and teretial tracts in ap- proaching the macromyelon, diverge and expand into a fibrous stem, which, arching over the fourth ventricle, developes the central transversely folded lobe, answering to the cerebellum of the Shark (vol. i. fig. 187, c) and Bird, and expands into lateral lobes 58 Vertical section of the median lobe of Cerebellum and Macromyelon. characteristic of the Mammalian class. The myelonal tracts, which in describing the brain from behind forward may be said to enter into the formation of the cerebellum, fig. 66, r, leave it, after some expenditure and exchange of substance, as ' departing ' 1 The progress of chemistry has lent new and valuable aids to the unravelling of the minute, but physiologically most interesting, structures of the myelon and macro- myelon. A solution of chromic acid is one of the best for preliminary immersion of slices of their tissues for a few weeks ; these, if afterwards put into alcohol, are hardened, but become less brittle than if kept longer in the acid. CEREBELLUM OF MAMMALIA. 89 restiform tracts, ib. t, continued into the basis of the mesence- phalon, forming also those called f processus cerebelli ad testes,' united above by the thin layer of medullary matter called ' valve of Vieussens,' fig. 49, B. The progressive increase of the lateral lobes is attended by corresponding developement of the system of transverse or arciform fibres constituting the ' pons varolii,' which, entering the cerebellum at the ' infero-lateral ' or ' sernilunar fissure,' fig. 64, h, i, interblend with the longitudinal ( entering ' and 'departing' columns, and constitute the commissural part of these lobes. In Anthropotomy the part where the formative and commissural tracts join on entering the cerebellum are collectively called its ' cruSj'the tracts being its constituent ( peduncles ; ' thus the enter- ing or posterior and restiform tracts, which are the ' homotypes ' of the ' crura cerebri,' are termed the ' inferior or posterior peduncles,' or ' processus ad medullam oblongatam,' fig. 66, r ; the emerging restiform tracts, called ' processus ad cerebrum,' and ' processus ad testes,' are the ' superior or anterior peduncles,' ib. t ; whilst the entering fasciculi of the ' pontal or varolian com- missure' are the 'middle peduncles' or 'processus ad pontem,' fig. 64, ?'. 'These latter are porportionally least in the lowest, and largest in the highest, species of Mammals. In all, the formative columns on entering the white axis receive grey or ' recruiting ' matter for the developement of accessory fibres, relating in size and com- plexity to the increase of the cerebellum, and chiefly of its lateral lobes. In the Monotremes, figs. 51 and 52, the 'pontal' or cerebellar commissure is a thin layer of transverse fibres of small antero-posterior extent ; the true character of the real ' crura cerebelli,' or formative fasciculi, is here well exemplified. The cerebellum, fig. 38, b (Echidna), consists mainly of the median lobe, which being transversely folded presents in vertical sec- tion that arrangement of grey and white matter called ' arbor vitas.' In the Marsupial Order, the cerebellum presents close-set, sub- parallel, transverse convolutions ; few in the climbing Koalas and Opossums, fig. 46, c, more numerous in the locomotive Kanga- roos : it is remarkable, as in Monotremes, for the large propor- tional size of the median or vermiform lobe as compared with the lateral lobes, especially in the carnivorous and insectivorous Marsupials, where this condition is associated with a corresponding diminution of their commissural band as shown in the view of the base of the brain of an Opossum, fig. 53, b. In the Kangaroos, ANATOMY OF VERTEBRATES. Perameles, Phalangers, and Koala, the hemispheres or lateral lobes of the cerebellum are characterised by a small subspherical lateral process or appendage, , Didelphys, and fig. 75, B, Pliascolomys, in the Marsupial order ; by fig. 79, Lepus, and fig. 80, 8, 9, Cavia, in the Rodentia ; and by fig. 67, Talpa, in the Insecti- vora. Both Z?/- and Liss-enccphala manifest their inferior posi- tion in the present class, and affinity to oviparous Vertebrates, by the larger proportion of the mesencephalon (fig. 46, o) to the pros- enccphulon, than in Gyrcncephala. In most Marsupials (Dasy- urus, fig. 72 ; Didelphys , fig. 73), in many Rodents (fig. 81, Lepus ; fig. 80, Castor), in all Insectivores (fig. 76, Rliynchocyon), and in Bats, the bigeminal bodies are more or less exposed between the cere- brum and cerebellum. As in Amblyopsis (vol. i. p. 278, fig. 175), so in Talpa, the optic lobes, fig. 67, c, do not show a reduction of bulk commensurate with that of the visual organ ; yet there is a de- gree of such relationship in Mammals. Thus the Ungulates which have large eyes have the optic lobes or nates, fig. 68, a, proportionally larger than they are in a Carnivorous quadruped with a similar-sized brain. In both the ' testes,' ib. b, are broader, but in Felis they also rise higher ; whilst in Un- gulates, and especially Ruminants, the 6 nates ' show the greater vertical developement. 1 In all Carnivores the ( testes' have a minor antero-posterior extent than the ' nates.' The white bands or tracts ( f brachia ' in an- thropotomy ), extending along the outer sides of the bigeminal bodies o to the thalami and com- mencement of the optic tracts, fig. 68, d, are prominent in the higher Quadrumana and in Man. In most Gyren- cephala the white fibres continued from the optic lobes develope an oblong nodule, ib. e, also containing grey matter (' corpus geniculatum ' of anthro- potomy), which in the human brain is divided into an external and internal portion. The f crura ccrebri ' formed by the pre- and post-pyramidal 1 This difference I exemplified in the preparations, nos. 1326 A and 1826B, xx. vol. iii. p. 30. Mcsenceplialon, upper view, Horse. PROSENCEPHALON OF MAMMALS. 99 and ' teretial ' tracts, expand in passing beneath the bigeminal bodies, and receive accessions from grey matter continuous with that of the macromyelon, but so dark as to have received the name ( locus niger ' when exposed in section. They are divided by the third ventricle, and swell out respectively at their upper part, through the superaddition of formative neuriiie, into the bodies called ' thalami optici,' fig. 68, c, figs. 71 and 75, t. The free surface is white, but the grey matter constitutes their chief bulk, and is partially divided by the longitudinal fibres into an outer and an inner portion : from the latter the soft commissure is continued. The optic tracts, fig. 68, d, commencing at the optic lobes and geniculate bodies, bend round the outer and back part of the ( thalami,' from which they derive accessory filaments to form the optic nerve. In connection with the mesencephalon must be noted the tract of white fibres continued from the fornix, on each side the third ventricle anterior to the soft commissure, to a nodule, conspicuous in Gyrencephala behind the infundibulum, and forming a pair (' corpora albicantia' in anthropotomy) in Apes, fig. 112, and Man. 208. Prosencephalon. As the 'crura cerebri' enter the pros- encephalou, they are augmented by further accessions of formative neurine in masses which in the human brain have received the names ' nucleus tremreformis,' ( nucleus lenticularis,' and ( nucleus caudatus.' The latter projects into the prosencephalic ventricle, as the ' corpus striatum,' figs. 70, s, 75, r. But this name extends or applies also to the deeper-seated grey masses, w r hich are so in- terblended with the diverging white fibres as, in section, to give alternate white and grey strias. The accession of white fibres from these formative nidi, diverging to form the basis of the cerebral hemispheres, causes the form expressed by the term 6 fibrous cone,' fig. 66, c. The grey matter again appears as a thin superficial covering or ( cortex ' of the expansion of the white fibres : and this grey matter contains cells similar to those in the corpus striatum. In most Ly- and Liss-encephala, and in a few of the smallest kinds of Gyrcncepliala, the prosencephalic vesicles retain the out- ward uniformity of surface which they have in birds and reptiles : unlike those of the mes- and ep-encephalon, they are so little united together that they are called and seem to form distinct ( hemispheres.' These are connected together in all Mammals as in Birds by the cord-like fasciculus of transverse fibres, figs. 69 and 73, c, called e anterior commissure.' But the main dis- tinction lies in the superaddition to the ( diverging ' or ' crural ' H 2 100 ANATOMY OF VERTEBRATES. fibres of other t commissural ' tracts either ( longitudinal.' con- O * necting parts of the same hemisphere, or ' transverse,' and bringing a greater proportion of the two hemispheres into mutual com- munication. But there are steps in this differentiation. Eacli hemisphere of the cerebrum begins as a vesicle of neurine, the cavity of which receives the growth from the ' crura ' forming the ' corpus striatum.' This, in Birds, mainly fills the ( ven- tricle ' or remnant of the primitive cavity of the sac. But, in Mammals, the w r all of the vesicle is augmented bv folds, of which CJ * the first and most constant is pushed from the mesial or inner side of the ventricle into its cavity, giving rise to the convexity, figs. 70, 71, h, fig. 75, n, representing the part called ( hippo- campus ' in anthropotomy, The ( fissure upon which the hippo- campus is folded ' 1 is numbered 4 in the ' Table of Cerebral Fissures,' p. 136, as in fig. 69, et seq. In Lyencephala it extends from the fore part of the inner sur- face of the hemisphere backward and downward in a curve with the concavity toward the centre or ' nucleus cerebri,' fig. 69, b. It is not, however, a mere doubling of the wall of the hemispheral vesicle ; longitudinal fibres are de- veloped therein for commissural office ; they cause a definite production of the lower part of the fold within the ven- tricular cavity called hippocampal band (t&nia hippocampi}, or, because in Man it is plaited, ' corpus frmbriatum : ' its im,er surface of hemisphere, vertical m f er ior hinder termination is in the section of brain, Ormthorhynchus. ' pes hippocampi ; ' its upper or anterior one becomes the ( posterior pillar ' of the fornix. ( Fornix ' is the anthropotomical term for the anteriorly continued and transversely connected longitudinal fibres of the hippocamp : the ' posterior pillars,' fig. 69, a, one from each hemisphere, converge as they advance, are united by a commissure of their own, ib. o, beyond which some fibres pass forward and radiate upon the inner surface of the fore part of the hemisphere ; while others bend down, as the f anterior pillars ' of the fornix, pass between the anterior commissure, ib. c, and the nucleus cerebri, b, and terminate in the mammillary body already mentioned. Delicate fibres, running on the inner surface of the hemisphere at right angles to the line of the hippocampal fissure, are con- tinued into the ventricle, where they cover the longitudinal fibres 1 So defined in i.xx'. p. 90 (1837) PROSENCEPHALON OF MAMMALS. 101 developed in the hippocampal fold,, and which form the main part of the hippocamp and its anterior extension. 1 This fold and its concomitantly developed longitudinal and transverse or arched fibres, constitute a great and abrupt dis- tinction and rise in structure in the Mammalian brain as com- pared with the Avian one, and indicate that birds are an offshoot from the lower Ovipara, forming a branch apart. 2 In Ornithorhynchus the postero-inferior parts of the hemispheres are brought into connection with the antero-internal parts by the longitudinal fibres, while the antero-internal parts of the hemispheres are connected with each other through the transverse fibres at the approximated anterior ends of the folds, where the stratum connecting those ends together, and radiating the fibres upon the inner surface of the anterior lobes of the hemispheres, and over the inner wall of the ventricle, is thickest. 3 The greater part of the hemispheral cavity or ventricle is overarched in Lyenccphala by the inner leaf of the hippocam- pal fold, and its developements called ' trenia hippocampi ' and 6 fornix.' The transverse fibres connecting the taenia hippo- campi and terminating that body anteriorly in Lyencephala, are carried, in the ascending Mammalian series, by the growth of the hemispheres anterior to them, as it were by a movement of rotation, from before upward and backward, until, in Man, they become the ' psalterial fibres ' which connect the posterior ( genu ' of the corpus callosum with the ( trenia hippocampi,' these being compared to the ' frame ' and the transverse fibres to the 6 strings ' of the harp, by the old anthropotomists. The super- addition of cerebral matter above and anterior to c, figs. 69, 73, is associated with transverse commissural fasciculi, progressively added, from behind forward, and now overarching the lateral ven- tricles, and fulfilling all the functions, relations, and definitions of the anthropotomical 'corpus callosum,' figs. 78, /, and 123, c. Its hind part is embraced by the ( callosal convolution,' ib. o. 4 1 These fibres are shown at x, fig. 4, pi. vii. LXX'., which gives a view of the hippo- campal fold from the ventricular or 'lateral' side, as ' part of a thin stratum of medul- lary fibres arching over the hippocampus major, and continued therefrom into the internal wall of the ventricle,' p. 95. 2 If we could examine the brains of Dinosauria or Dicynodontia, the actual gap in the series of cerebral structures might be better filled. 3 From this point in the lowest (Lyencephalous) mammals, as in the embryo of the highest, the growth of the great supraventricular body of transverse commissural fibres forming the ' corpus callosum ' begins : ' Anterior fibres of the " tasnia hippo- campi v continued into the anterior lobes of the hemispheres.' LXX'. p. 95, pi. vi. figs. 4 and 6, o'; and pi. vii. fig. 4, x. 4 The part marked B in the Echidna has become the part marked N in Man. Pis. xxxvi. and xxxviii. of XLIII". 102 ANATOMY OF VERTEBRATES. 70 Lateral ventricle, Echidna. Such urc the essential characters of the Mammalian ( prosen-- cephalon.' The chief modifications of the Mammalian brain, as above characterised, will next be noticed in the different leading groups of the class. A. Lyencephala. In the Ornithorhynchus, the brain, figs. 52 and 69, is to the weight of the body as 1 to 130 ; the hemispheres arc triangu- lar, depressed, the broader posterior part over- lapping the optic lobes, and reaching to the cerebellum. With the exception of the hippo- campal fissure, fig. 69, 4, and the depression lodging the rhinencephalic crus, the surface is unbroken or smooth, with a few vascular im- pressions diverging from the fore part. The medulla oblongata is broad and depressed ; the corpora pyramidalia, fig. 5 1 , a, are in very low relief ; the corpora olivaria, a, expand as they advance ; they are crossed anteriorly by the ' corpora trapezoidea,' b, which are large ; the ' pons,' c, is narrow : anterior to it is a large ganglionic body, c', from which issues the husje trigeminal nerve, 5. The longitudinal groove be- o o * o o 71 tween the optic lobes is shallow ; it is wanting in the small and IOAV ( testes.' The hippocampus is the chief prominence within the ventricle of the hemisphere ; the corpus striatum is long and narrow. The brain of the Echidna, fig. 71, is relatively larger than in the Ornithorhynchus y and the exposed outer surface of the hemispheres is extended by con- volutions. The cerebral hemi- spheric cavity is mainly occupied in both Monotremes by the ' hip- pocamp,' fig. 70, h, which con- stitutes a great part of its floor as well as inner Avail. This, with much of the hippocamp, is removed in fig. 71, to show the proportions of the 'corpus stria- turn,' 5, and to bring into view the thalami, t ; these are divided from the ' nates,' r, by a linear groove ; the ( testes,' s, are half the size of the f nates,' and the median longitudinal groove, which is shallow between the nates, is not continued further liralu and lateral ventricle, hippocampus removed Echidua. PROSENCEPHALON OF MAMMALS. 103 back. 1 Like the water-shrews, the Ornithorliynchus has a smooth cerebrum; the JEchichia, like the Great Ant-eaters and the Sloths, has a convoluted one. Besides the long and deep ( hip- pocampal fold,' the fore part of the mesial surface shows a beginning of the supercallosal one ; behind which it is also notched vertically by the mesial ends of the upper transverse folds, 2 fig. 71. Of these, three nearly parallel ones extend across the broad posterior part of the upper surface of each hemisphere, their outer ends inclined forward ; anterior to them is a larger convolution bent upon itself so as to form the inner boundary of the anterior half of the upper surface. In the angle of the above are two oblique folds inclining ( mesiad ' toward the contracted fore part of the hemisphere. The base of the brain, fig. 52, shows a few short foldings of the surface of the great natiform protuberances, b'. The principal folds sink about a line's depth into the substance of the cerebrum. The rhineiice- phalon is enormous, ib. R. Some of the fibres of the great anterior commissure bend forward, and are continued into each of its crura. The outer part of the crus, ib. i , continued from that of the prosencephalon, emerges from the fore margin of the natiform protuberance, from which it has a reinforcement of fibres ; the inner division, tumid with added grey neurine, ib. i b, is also very broad. The prosencephalic cavity or ' ventricle ' is con- tinued into the rhinencephalon, and is exposed in fig. 52, by re- moval of the thin floor which rests upon the large 6 cribriform plate.' The ( pineal ' and pituitary (ib. p) appendages of the prosencephalon offer no monotrematous characters. There is not that difference of size between the Ornitho- rliynchus and Echidna which would lead us to connect therewith the convolution of the hemispheres in the latter animal ; what is known of their habits suggests no superiority of psychical power and resource in the land- over the water-monotrematous Insectivore. Increased extent of the walls of the hemisphere in no 1 My observations on this state of the ' corpora quadrigemina ' in Monotremes accord with those of Laurent and Eydoux on the Echidna, and of Meckel on the Ornithorhynchus. ' En comparant les tubercules quadrijumeaux de 1'Echidne a ceux de 1'Ornithorhynque, nous avons facilement constate ce que 1'a deja ete par Meckel pour ce dernier, c'est-a-dire qu'on ne peut pas distinguer les tubercules posterieurs des anterieurs, et que ce que Meckel a remarque chez 1'Ornithorhynque et exprim6 en ces termes : " Eminentia quadrigemina magna, posterior tamen vere percipienda, ut fere bigemina esset," est encore plus prononce dans les tubercules du cerveau de 1'Echidne, qui sont reellement bijumeaux simplement.' LVII". p. 164. - Well given in LVII". pi. ix. fig. 4 : omitted ill the diagram of a similar section in XLIII". pi. xxxvii. fig. 7. 104 ANATOMY OE VERTEBRATES. degree influences the developement of a supraventricular trans- verse commissure ; the seeming small one exposed at o, fig. 7 1 , is hippoc'ampal or psalterial. This low phase of Mammalian brain- growth is essentially related to the common monotrematous con- ditions of generation. The brain bears a small proportion to the body in the Marsupial order; in the Ursine Dasyure, fig. 72, it is as 1 to 520; in the Wombat, as 1 to 614; in the great Kangaroo, as 1 to 800. In smaller Kangaroos the disproportion is less ; thus in the Tree- kangaroo (Dendrolagus inustus) I found it as 1 to 250. The brain is relatively largest in the smaller species of Petaurists and Phalangers. The cerebral hemispheres do not extend over the cerebellum in any of the species, and in some, as the Dasyures and Opossums, they leave the optic lobes exposed. In the Phalangers and Petau- rists, the Opossums, Perameles, the insectivorous Phascogales, and the smaller Dasyures, the exposed surface of the cerebral hemispheres is unconvoluted. In the Dasyurus ur sinus, fig. 72, b, this surface is broken by a few slight indentations, two of which may indicate the beginnings of the ( medi-lateral ' longitudinal folds. In the Wombat an ectorhinal fissure bounds the outer side of 72 the olfactory tract at the base of the brain ; ! from the anterior moiety of this fissure three or four smaller ones curve up- ward upon the sides of the hemispheres, one of which answers to the ' fissura Syl- vii,' 2 but is less defined than in the Kan- garoo. On the upper surface a short transverse fissure marks off the outer part of the anterior lobe of the cerebrum, and behind this each hemisphere exhibits a few detached shallow fissures. The American Opossums show a range in size from that of a mouse to that of a cat, and the Australian Dasyures rise from the same diminutive extreme (Antechinus pusillus] to the size of the wolf ( Tliyla- cinus). But the cerebral hemispheres are as smooth in Didel- pliys Virginiana* as in D. (Philander, Microdelphys) murina\ and the great Ursine Dasyure, fig. 72, shows but a few short and shallow indentations of the exposed cerebral surface. 4 Thylacinus 'd Brain of Dasyurus ursinus. . i.xx' pi. v, fig. 8. 2 Ib. fig. 3. 8 Ib. fig. 6. 1 Ib. fig. 5. PKOSENCEPHALON OF MAMMALS. 105 73 B Didelphys Virginian;!. has the anterior apex of the hemisphere marked off by a deeper transverse fissure, extending to the inner surface. In the Her- bivorous Marsupials the fissures are more definite, deeper, and rather more numerous in the larger (Macropus major, fig. 74) than in -the smaller species (Hypsiprymnus). All Marsupials have the hippocampal fissure, fig. 46, 4, fig. 73, z, coextensive with the antero-posterior range of the prosencephalic cavity, and arching over all the commissural apparatus of the hemispheres. The concomitant extent of the convolution (hippocampus major) is shown in LXX'. pi. vii. figs. 3 (JDidelpliys) and 4 (Macropus), in the exposure of the ventricle from the outer side. In Didelphys, fig. 73, the surface of the hemisphere above the fissure is feebly impressed by blood-vessels ; in Tltylacinus there is a short fissure above the back part of the hippocampal one ; in Phascolomys and Macropus there is also an anterior one which bends or bifurcates at its fore part. 1 These fissures mark the level of the roof of the lateral ventricle ; the surface below forming the thin mesial o wall of the cavity, fig. 75, q, which in the higher Pla- centals is defined, as the ' sep- tum lucidum,' by a corpus callosum from the part above, On the upper surface of the hemisphere, in Macropus ma- jor, a longitudinal part of the fissure, fig. 74, s, marks off a medial convolution, /, at the anterior half, and occasion- ally it is prolonged backward by the fissure, 10, as in the left hemisphere of fig. 74. But there is continued from 8, in both hemispheres, a fissure extending outward, which bounds behind the part of the hemisphere impressed by the ( sylvian fissure,' 5. The 74 1-2 Brain of Macropus major. 1 LXX'. pi. vi. figs. 4 and 6, The Aye-aye agrees with the Lemurs and Aye-aye. all Quadrumaiia in this respect ; the homology of b, fig. Ill, with the basirhinal fold, figs. 52, U ' , 82, k, in Ly- and Liss-encephala, is masked by such interruption of the fissure, 2, in Quadrumana. In Lemur proper the lateral fissure (between I and c/, fig. 116) is shorter than in Chironujs and is not distinct from the supersyl- ..vian : in some species it bends outward more abruptly, in so far marking more plainly the coronal fissure, 12, as in higher Quadru- mana, and indicating a longer anterior lobe than in Chiromys : a frontal fissure, 14"', appears there. In the main we recognise in the cerebrum of Chiromys and Lemur, as in that of Carnivora, the primary division of the upper mass of the hemisphere into sub- parallel folds, medial, /, medilateral or supersylvian, n, and sylvian, e ; but, shorter and more bent as they recede from the middle line ; with indications of a longer anterior lobe or tract. The hippocampal fissure is prolonged into a f post-hippocampal,' fig. 110, 4', as in higher Quadrumana. In the diminutive Platyrhine (Midas, GeofFr., figs. 109, 116) the smoothness of the upper surface of the hemisphere is broken only by the extension thereon of the sylvian fissure, 5. In the next stage ( CaUithrix) a ' postsylvian fissure,' ib. 9, is added, and the hemisphere may also show a longitudinal fissure, fig. 116, 8, 12, curving, like the supersylvian, over the end of the sylvian, n, and postsylvian, 9, fissures ; but which, in relation to tH inter- hemispheral fissure, corresponds rather with the lateral fig. 89, n, of Carnivora : the large anterior tract may show a short frontal fissure, fig. 104, H'". In all the small Platyrhines (Midas, Calli- 1 cir. This has also the character of the ' supcrcallosal,' 7', fig. 117. 126 ANATOMY OF VERTEBEATES. Ill thriz, fig. 109) the sylvian fissure, 5, and fold, e, are directed more obliquely from above and behind, downward and forward, than in the Aye-aye, ib., and most Lemuridaj : this character appears to be due to the preponderating growth of the frontal lobes, and becomes more marked as the Quadrumana rise in the scale. AVe next find that each hemisphere is divided into an anterior, middle, and posterior tract or region by two deep and extensive fissures, 12 and 13, Macacus, fig. 109, and Cebus, fig. 116, which, from their respective correspondence in position with the coronal and lambdoidal sutures, bear the same names. In Cebus the sylvian fissure, fig. 116, 5, is overarched by a subangular one defining the fold, g ; from the angle a fissure, 13, extends to the inter- hemispheral one, and is continued deeply down the inner or mesial surface. Out- wardly the lambdoidal fissure, 13, defines and undermines a posterior part of the hemi- sphere, by raising w^hich the continuation of the postsylvian fold, jf, may be traced beneath it. The chief difference between the cata- rhine and lemurine hemispheres, at the inner surface, is the superaddition and interposition of the entolambdoidal fissure, is', between the post-hippocampal, 4', and marginal or super-callosal, 7',fig. 117; the entolambdoidal being sometimes continued into the post- hippocampal fissure, as in fig. 118, is' 4'. The almost transverse fissure, fig. 116, 12, di- vides the larore anterior from the middle lobes. CJ In the latter, however, may be recognised the short tract, I, w, combining the ( medial ' and ' medilateral ' folds, but more transversely disposed than in Carni- vora ; pushed out, as it were, by the backward growth of the anterior lobe. Secondary fissures there indicate frontal, n, mid- frontal, n" ', and superfrontal, n f , folds. One or two longitudinal occipital fissures mark out corresponding folds, q" ', q" f . The ecto- rhinal fissure, fig. 111,2, sinking into the sylvian one, 5, may have a continuation in the anteropostcrior fissure, ib. 2', which divides the ' natiform protuberance' into a medial or basirhinal, b, and a lateral moiety, f . In most Catarhines the coronal fissure, 12, figs. 114, 116, extends, from within, more obliquely forward and outward; the homologues of the platyrhine fissures and folds are clearly seen, as marked by the figures and letters in Macacus and Cebus, Under surface of cerebral hemi- sphere, Mitcacus. PROSENCEPHALON OF MAMMALS. 127 112 fig. 116. Secondary fissures subdivide the orbital as well as the frontal and falcial surfaces of the anterior lobe : the surface resting on the orbital plate of the frontal bone, in the Orang's brain, fig. 112, shows the following con- volutions : ( postorbital,' o, mid- orbital, o', entorbital, o", ect- orbital, o' f , and antorbital, o*. That which lies external to the rhinal fissure or depression is not subdivided into ectorhinal and entorbital folds as in Man, fig. 120, d, o". Similar secondary chinks furrow the occipital lobe, on the tentorial surface of which the tentorial fold, fig. Ill, r, the entotentorial, r', and ecto- tentorial, r" , are now defined by the fisSUreS, 18, 18', IS''. These Base of the I,., Orang-utan. folds are more or less continuous with the basirhinal, b, and sub- sylvian, f, tracts. The increasing number of secondary fissures ..and the greater depth and more winding course of the pri- mary ones mainly characterise the brain in the Orang (vol. ii. fig. 148) and Chimpanzee, fig. 114. The tract between the interhemispheral and supersylvian fissures is subdivided into medial, /, medilateral, m, and supersylvian, g, folds, fig. 116, Chimpanzee : we have evidently here the corresponding parts of the hemispheres that form these folds, or parts of them, in Carnivora. D. Archencephala. The same principle carried abruptly to an extremely greater degree, as in figs. 115, 116, Homo, associated (as compared with Gorilla, e. g.,) with a greater proportional bulk of the brain to the body, and with a still greater proportional size of the cerebrum to the rest of the brain, characterise the Archencepha- lous subclass, from the lowest varieties (Australian, Boschisman, Hottentot) to the highest. These proportions have thoroughly stood the severest tests, as where the diminutive female in such varieties has been selected to exemplify the brain-characters, with a view of reducing the chasm between the gyr- and arch- encephalous brains to a minimum. Before entering into the details of the complex convolutioual surface of the human cerebrum, I may premise some recapitu- latory remarks. 128 ANATOMY OF VERTEBRATES. c We are guided to the homologous parts of the cerebral hemi- spheres throughout their range of dev elopement in the Mammalian class, in a great measure, by their relations to other parts of the bruin. The portions more immediately surrounding the cerebral crura, 1 those which overarch the corpora striata and thalami and overlie the olfactory crura, or at least their beginnings, can hardly be doubted to be corresponding parts in all Mammals. The inferior prominences behind the " crura rhinencephali," forming the " protuberantias natiformes" of some anthropotomists (Z/ basi- rhinal fold), the inverted hippocampal fold, its labia and fissure, are plainly determinable throughout the class, as is also the pylvian fissure, 5, somewhat less constant, dividing the part of the hemisphere terminated by f, figs. 113 and 115, and sometimes called (i inferior lobe," from the part which is in front of it : the superaddcd cerebral substance to the above more constant parts of the hemispheres is that which, in Man, advances, overlaps, and extends beyond the olfactory lobe, and that which extends backward in like relation to the cerebellum. ( If one can predicate homology of any folds or fissures of the cerebral superficies, throughout the Mammalian class, it must be at the above-defined middle part of the more developed hemispheres, and especially at those fissures, viz. 2, ectorhinal, 4, hippocampal, 5, sylvian, 7, callosal, 7' ', supercallosal, that are the most constant throughout the series. The upper surface of the hemispheres, as we have seen, is subject to different ways of folding : in Echidna the plaits go across, in Fells along it, while in Bos and Slmia they run askew, yet contrariwise ; in one from behind forward and inward, in the other forward and out- ward. It may seem, to some, that each leading division of Gyrcncepliala should have its own system of nomenclature and symbolism of brain-folds that homologous convolutions can only be satisfactorily determined within the limits of such groups as Unfjidata, Unguiculata, Quadrumana. In a degree this is true ; the grounds of homology are such in regard to some folds (& and 7') as to leave room for difference of choice ; but there are others that have a surer basis for homologising. Take, for example, the " sylvian fissure," 5 : the fold e, that immediately overarches and forms it, is determinable : one part of the fold forms the anterior, the other the posterior, lip of the fissure : they are united or continuous by the overarching part in most Unyuiculates and Ungulates. The homology of the sylvian fissure and fold is not 1 Subsequently defined as ' prosencephalic.' PROSENCEPHALON OF MAMMALS. 129 cbscured by the minor intersylvian convolutions, which are ex- posed in the Sheep and Elephant, and are concealed in higher Quadrumana and Man, where they constitute the " gyri breves " of Arnold ; l nor is that of the anterior lip by the interruption of the ectosylvian fissure, s', in the Cat, fig. 91, whereby the sylvian is divided into parallel vertical folds, which, w T ith the intervening sylvian fissure, are overarched by the higher supersylvian fissure, ib. 8. In Quadrumana the posterior part of the supersylvian fissure, fig. 109, 8, sometimes runs into one, 9, behind and parallel with the sylvian, 5. In Stenops the detached " post-sylvian," 9, is short and straight, as in the Cat. 6 In the Marmozets (Midas, Geof. Hapale, Bl. Jacclius vulgar is} the sole superficial fissure on the exposed surface of the hemi- sphere is the sylvian, figs. 109, 116, 5, and this determines the con- tiguous part of the hemisphere, e, to be the homologue of the sylvian fold. When the postsylvian fissure appears, as in CaUitlirix, fig. 109, 9, the postsylvian fold, /, is defined : it is certain that we now have the homologues of the folds so named and numbered in Unsmiculates, ficrs. 90-92 ; and the advantage O J O ' O of their determination would be lost were we to apply new names to these folds and fissures as if they were distinct and superadded parts in the quadrumanous and bimanous brains. The next fissure which appears, in the Quadrumana., answers to that marked n, 8, in Putorius, fig. 87, which is longitudinal and bends more or less outward anteriorly : it divides, in fig. 116, Callitkrix, 8, the cerebral surface above the sylvian and postsylvian fissures lengthwise, into two pretty equal tracts, and tends to mark off an anterior part or lobe of the hemisphere. ' Proceeding with the more typical Quadrumana, we find that the progressive expansion of the cerebrum, which has carried it backward over the cerebellum, and augmented the outward and downward extension of the part behind the sylvian fissure, has also added so much to the anterior lobes as seems to have pushed backward the rest of the hemisphere, and gives the sylvian, e, and postsylvian, f } folds a more oblique direction from above, downward and forward, than in most low r er Unauiculates. In the Otter, indeed, and Lion, the sylvian and presylvian fissures are similarly oblique : but the posterior part of the sylvian fold does not project outward so far beyond the anterior part as in Quadrumana : this development, together with the interruption of the supersylvian fissure, and the extension of secondary fissures at right angles and anterior to the sylvian fissure, tend O O v IX' VOL. III. K 130 ANATOMY OF VERTEBRATES. to mark the homology of the forepart of the sylvian fold in Quadrumana. Its upper part is now defined from the forepart or " anterior lobe " of the brain, by the fissure 12, figs. 109, 116, which, instead of being continued with or from the longitudinal one, as in Lemur, fig. 116, 8, extends from without, obliquely inward and backward, to or near to the interhemispheral fissure. It is that which, from being first well defined by the Italian anatomist } in the human brain, has been called " fissura Rolandi," but which I term " coronal," or " coronal part " of the medilateral fissure, in Ferines, figs. 88-92, 12.' In the side view of the human hemisphere, fig. 115, the fissures are indicated as follows: 2, ectorhinal, external to the cms rhinencephali, it is longer and more conspicuous in the lower Mammals, fig. 107, 2, 5, sylvian, 8, supersylvian, 9, postsylvian, 9', subsylvian, 12, coronal, 1.3, lambdoidal, 14, frontal (or post- frontal), u 7 , superfrontal, u", midfrontal, 14"', subfrontal, 14 X , ectofrontal, 17, occipital (or superoccipital), 17', exoccipital, 17'", ectoccipital. The folds or convolutions are : - - d, ectorhinal, e, sylvian, /, postsylvian, f, subsylvian, g, supersylvian, /, medial, m, medilateral (/ and m, as in Quadrumana, are less distinct from each other, as well as shorter and more oblique, than in Garni- vord), n, frontal (or postfrontal) n f , superfrontal, n" ', midfrontal, ft" 7 , subfrontal, n* , ectofrontal,^, lambdoidal, q, superoccipital, , lambdoidal, q, occipital, q", suroccipital, q"' ', suboccipital. The primary fissures on the internal (mesial) surface of the hemisphere, fig. 118, are 4, hippocampal, with its long bifurcate ir Vertical section, brain of Baboon. posterior extension, 4', 7, callosal, 7 X , supercallosal, 6, marginal, 1 13 7 3 entolambdoidal, here continued into the posthippocampal ; the supercallosal fissure, 7', bifurcates anteriorly, as inPapio, fig. 117, /' and Pithecus (vol. ii. fig. 149). The surface applied to the fore part of the falx is impressed by falcial, 1.3, and subfalcial, \z>' ', 1 This is seldom so distinct or continuous as in the larger ungulates. K 2 132 ANATOMY OF VEBTEBRATES. fissures, more or less parallel with ?'. The principal folds defined by the above fissures are : a', posthippocampal, k, callosal, //, supercallosal, //, marginal, h', postmarginal, t, falcial, t', subfalcial (which is the inner surface of c, entorhinal), ;/, entolambdoidal, .s-, septal. Anthropotomists have primarily divided the hemispheric masses 118 Vertical section, half nat. size, Human Brain. XL". into groups of convolutions or ' lobes:' some into three, viz., the 6 anterior,' e middle,' and ( posterior ' lobes ; others into five. These latter are termed f central ' (lobus centralis), ' frontal ' (lobus frontalis), ' parietal ' (lobus parietalis), ' temporal ' (lobus temporalis}, ' occipital ' (lobus occipitalis}. The central lobe (' Stammlappen,' Huschke) answers to the f Insel' of Reil, and is not visible outwardly; it includes the ( gyri breves,' and is, by some, held to be peculiar to Quadru- mana and Bimana (but see figs. 117, 11 8, /',/*'). The ( frontal lobe,' fig. 119, r, includes so much of the anterior lobe as lies in advance of the ( frontal fold,' n, n, and is subdivided above into the superfrontal, n' 9 midfrontal, n" ' , subfrontal, n f " ', ectofrontal, ?i x , and ' prefrontal,' % x x , folds : it is an artificial division of the part, most naturally defined, both in Quadrumana and Man, by the coronal fissure, 12, from the rest of the hemisphere. PEOSENCEPHALON OF MAMMALS. 133 The f parietal lobe,' P, includes the frontal fold, ?i, n, the anterior and superior parts of the sylvian, e, and supersylvian, y, folds, with the medial, /, and medilateral, m, folds. The ( temporal lobe,' T, in- 119 eludes the posterior part of the sylvian fold, the postsyl- vian, and subsylvian folds, fig. 115, f,f, and also part of the supersylvian fold, g. The l occipital lobe,' o, is a more natural division, includ- ing all the part of the hemi- sphere which lies behind the lambdoidal fissure, is. The anterior lobe has three surfaces, one applied to the calvarial part of the frontal bone, another to the orbital plate, a third to the falx. Each of these are impressed by secondary fissures, which I have called ' frontal,' ( or- bital,' and ( falcial,' accord- ingly. The frontal fissures mainly affect a longitudinal direction, but run behind into a transverse one. This is the * frontal,' or ( postfrontal,' fig. 119, u ; it is more or less extensive and parallel with the coronal fissure, ib. 12. The Constant OI tlie lOngltU- superior surface of the right hemisphere of the adult fisSlireS pretty equally human brain, two-thirds nat. size. bisects the frontal surface; it is the ( midfrontal ' fissure, fig. 116, 14"; the fissure above or internal to it is the ( superfrontal,' u', that beneath or external is the ( subfrontal,' fig. 115, 14 /X/ ; beneath this again and upon the outer and back part of the frontal lobe is a deep and constant longitudinal fissure, usually bifurcate, the ectofrontal, ib. 14 X . The fissures on the orbital surface present much analogy to the frontal ones. The posterior one is transverse and usually curved with the convexity forward ; it is the orbital or postorbital, fig. 120, 16 ; the most constant of the longitudinal fissures which 134 ANATOMY OF VERTEBRATES. 120 extend forward from the orbital one, I call ( midorbital,' ib. 1 6' ; that to the inner side is the entorbital, IG"; that to the outer side, the ectorbital, IG'" ; a transverse fissure anterior to these is the antorbital one, u x . The ccto- and ento-rhinal fis- sures, 2, 3, distinct posteriorly, run into each other where they form the groove lodging the slender ' crus rhinencephali ' of the human brain. The cerebral folds thus marked out arc the entorhinal, c (which is the un- der surface of the subfalcial, fig. 118, t') 9 the ectorhinal, d, which, in Ly- and Liss-ence- phala, Unyulata, and most Car- niuora, is continued backward, uninterruptedly, into the basi- rhinal tract, b ; external to d, fig. 120, are the postorbital, o, midorbital, o', entorbital, o", ectorbital, o f " ', antorbital, o x . The postorbital tract passes backward into ' Reil's Island.' The ectorbital, 0"' menyes into * * o the ectofrontal. rc x , fio*. 119, of ** * O ? which it may be called the un- der surface : attention has been called to the coincidence of loss or defect of speech with lesion in that fold or locality of the brain. 1 The tracts connecting some of the folds of which the homology with those of lower mammals is determinable, are noted, in anthropotomy, as ( annectant gyri ' (' plis de passage,' Lix"). On the falcial surface of the frontal lobe the most constant fissures are two that aifect a longitudinal course ; the upper one, which seems to be a continuation of the ( marginal ' fissure, is the * falcial,' fig. 118, 15 ; the parallel one below is the i subfalcial,' is'. ^The posterior lobe of the hemisphere, marked off by the lamb- doidal fissure, 13, has three principal surfaces : one applied to the superoccipital plate, one applied to the falx, and one resting on the tentofium. 1 LXXH" and LXXUI". Under surface of hemisphere, human cerebrum. PPvOSENCEPHALON OF MAMMALS. 135 121 On the occipital surface are several but irregular fissures, which, from their position, may be termed mid-, super-, ent-, and post-occipital; they define, more plainly in Quadrumana than in Man, the lambdoidal, fig. 119, p, suroccipital, q", midocci- pital, q f , suboccipital, q"' ', and postoccipital, q*, folds. On the tentorial surface they affect a longitudinal wavy course, and are commonly three rn number; of these, the middle one is the e tentorial' fissure, fig. 120, is, the inner one the ( entotentorial,' ib. is', the outer one the ' ectotentorial,' is". On the surface next the falx, or septum dividing the hemispheres, fig. 121, the fissures have a radiating tendency from the anterior angle outward : the most constant and important of these, in Man, has already received the name of ' posthippocampal,' being a con- tinuation of that deep fissure the corre- sponding fold of which partly protrudes into the posterior horn of the ventricle, as the ' hippocampus minor ;' the rest I called ( septal ' fissures, reserving the term f falcial ' to those on the corre- sponding surface of the anterior cerebral lobe. The fissure above the ' posthippocampal ' is the ' septal ' fissure, 19; that beneath the posthippocampal is the ( subseptal,' i^' ; the fissure between the septal and entolambdoidal, is', fis- sures is the superseptal, 19'; their outer ends are frequently lost in a fissure following more or less extensively or interruptedly the posterior contour of the posterior lobe; this is the postseptal fis- sure, i'/"; it is peculiar to Man. The folds so defined on the sep- tal surface are : the entolambdoidal, p' 9 superseptal, s' ', septal, s, posthippocampal, a', subseptal, s" ', and postseptal, s'". The human brain, in its development, passes through stages in some degree like those which are permanent in and characteristic of the Quadrumana, in respect to its cerebral folds and fissures ; but it early manifests its distinctive archencephalous proportions, fig. 109, Foetus. About the twentieth week the fissures begin to ap- pear upon the upper surface of the hemispheres, fig. 116, three months' Foatus. After the ( hippocampal ' and 4 callosal ' have cleft the inner surface, and the ( ectorhinal ' and ( sylvian ' the under sur- face, the entolambdoidal ascends upon the mesial side of the upper surface (fig. 116, 13); the postsylvian, 9, appears; then a faint trace of the longitudinal fissure, fis;. 116, 14', indicative of the ~ ' O ' J midfrontal and ectofrontal tracts. The ( coronal,' fig. 113, 12, is Inner or septal surface of posterior lobe, human cerebrum. J36 ANATOMY OF VERTEBRATES. speedily followed by the f postsylvian ' 9. A more or less inter- rupted fissure divides lengthwise the sylvian or supersylvian fold, ib. g, from the median, /, and medilateral, m, tracts. The lamb- doidal fissure, 13, extends toward the outer part of the hemisphere : the pre-coronal tract of brain is fissured into subdivisions, chiefly longitudinal : the foetal brain, at seven months, figs. 1 13, 1 16, resem- bles, in superficial cerebral marking, that of the latisternal apes,ib., Chimpanzee, but is broader anteriorly, deeper and longer behind. In the foregoing summary we have seen that the fissures which break the surface of the mammalian brain are of different kinds, degrees, and values. Some, in the course of development and elevation of the primary masses, divide one from the other ; as the cerebrum from the optic and olfactory lobes, the cerebrum from the cerebellum, and this from the macromyelon. Some subdivide primary masses into symmetrical halves, as e.g., the inter-hemispheral fissure, the inter-olfactory fissure, and the shal- lower indent between the mammalian optic lobes or ' nates.' One or two fissures of the cerebrum make folds that project into the hemispheral cavity or ventricle, e. g. the hippocampal and, in Man, the posthippocampal : most are confined to its crust or wall, and of these, as I showed in 1833, some, from their relative con- stancy, depth, and symmetry, may be termed * primary,' while others are of ( secondary ' or inferior rank. The following are those which are noted by figures in the illus- trations of the present work :- CEREBRAL FISSURES, in the order mainly of their constancy in the Mammalia. Figures. 1. Interhemispheral. 2. Ectorhinal. 2'. Basirhinal. 3. Entorhinal. 4. Hippocampal. 4'. Posthippocampal. 5. Sylvian. 6. Marginal. 6'. Post marginal. 6". Prcmarginal. 7. Callosal. 7'. Supercallosal. 8. Supersylvian. 8'. Ectosylvian 9. Postsylvian. Figures. 9'. Subsylvian. 10. Medilateral. 1 1 . Lateral. 1 2. Coronal. 13. Lambdoidal. 13'. Entolambdoidal. 14. Frontal or Postfrontal. 14'. Superfrontal. 14". Midfrontal. 14'". Subfrontal. 14 X . Ectofrontal. 1.5. Falcial. 15'. Subfalcial. 16. Orbital or Postorbital. 16'. Midorbital. Figures. 1 6". Entorbital. 16'". Ectorbital. Antorbital. Occipital orMidoccipital. Superoccipifal. Entoccipital. Ectoccipital. Postoccipital. Tentorial. Entotentorial. Ectotentorial. Septal. Supcrseptal. Subseptal. Postseptal. 16* 17. 17'. 17". 17'" 17 X . 18. 18'. 18". 19. 19'. 19". 19'" The following are the cerebral folds which are indicated by letters in the illustrations of the present work, with the synonyms of original labourers in this field of anatomy :- PROSENCEPHALON OF MAMMALS. 137 GRATIOTLE. LIX". Partie anterieure du grand marginal. Orbital interne. Pli parietal ascendant. Pli temporo-sphenoidal. d d o N3 8 f 1 ^3 i-H P. H ' S . "^ c5 c3 r^ i ' jj Lobule quadrilaterale. Pli du corps calleux. Deuxienie pli parietal ascendant, et Stage superieur du grand marginal, ib. Premier pli parietal ascendant. Frontal superieur. Frontal moyen. Frontal inferieur. Orbital posterieur. ib. inoyen. ib. intenie. ib. exterue. Premier pli de passage externe, ou Stage superieur du lobe occipital. Pli interne du lobe occipital. Pli superieur du lobe occipital. Occipital moyen, et second pli de passage ext. Occipital inferieur, ct troisieme pli de pus- sage externe. Pli temporal inferieur. Pli temporal moyen anterieur. Pli temporal inferieur. Lobule occipital, ib. Pli temporal moyen anterieur. *c3 '> M 03 g a a (H bo d 2 LEUKKT. XL". Lobe d'Hfppocampe. in. P. Troisieme circonvolution postei'ieure. Crochet. *t* * Circonvolution d'enceinte de la scissure de Sylvius : its hind part is (in Man) . . i. P. Premiere circonvolution superieure. ii. P. Seconde circonvolution postirieure. in. P. Troisieme circonvolution posterieure. *** A. Partie interne de la troisieme circonvolu- tion anteiieure. I. Circonvolution interne qui se contourne sur le corps calleux. Circonvolution de I'ourlet, Foville. s' (and part of) circonvolution transverse medio-parietale. ib. s Premiere circonvolution supCrieure . in. A. Troisieme circonvolution anterieure. ii. A. Seconde circonvolution anterieure . I. A. Premiere circonvolution anterieure . f-t -t-> c/] a . . . . c "p m o o 1 ... 3 o J-. . .0 . I-H . - 1 , ^ CO r Q\ SH c3 . . > "T 1 b O> >> CJO .^3 DO "i o "^ . "3 2 . * cristato : gyrus fornicatus, Arnol< B.H S ^ ' ' ' S 3| 1 .2 | g 3,93 3 X " M |gh. s 1 .'5 ^ *~^ ^^ 'i-H 1 <3 O O ra tn Ili.i -i ...1 11 III L * fl a ^ 0> ^ .... C o a, i-4 to 'r cs'Co.s S 2 I ;i o Si I c2 Sg -g-3 o ' '45^ c3 >> c3 L ? uJ rb Cu p .0 O 5o ii ^ | -| fi o g Supersylvian . h Marginal Ou ( |"3 |l k f Supercallosal ."os ,2 n Frontal (or post-fi n' Snperfrontal n" Midfrontal . n f " Subfrontal . n* Ectof rental, r I _. Cg r* _ 2 fto ri -C-S SHO-^IS -3 S^S.S Ii It'll aslls Is I'll"! w S P ^ ^> =-

^ > - 1 ^ "rf '-2 ^ "S '? '2 3 3 '> % 1 -^ '3 IIHlll ||| * ^ ^ ^ -. ^ s q" Suroccipital q'" Suboccipital q* Postoccipital r Tentorial r Entotentoria] r" Ectotentorial s Septal . s' Superseptal s" Subseptal a/11 T5,N, J.-1 138 ANATOMY OF VERTEBRATES. Each hemisphere is a bag of neurine folded or laid upon its expanding stem, the hollow of the bag being the ventricle. This, in the embryo, is capacious and simple, the wall being very thin. It becomes thickened in different degrees at different places, most so at the upper and outer sides. The wall, thus thickened, pro- trudes at certain parts into the cavity, dividing and shaping it into parts or recesses which Anthropotomy calls ( horns,' from their curvature in Man. In lower Mammals the primitive cavity com- monly retains more of the general shape of the hemisphere, and in most Quadrumana, the lower more especially, the part accom- panying the broad supracerebellar expansion of the hemisphere is of corresponding capacity. The Orang, among Apes, still shows the primitive character of this part of the ventricle : in the Chimpanzee and Gorilla the growing walls reduce and begin to shape it as a f horn,' showing also a beginning of a protu- berance within it. In Archencephala the moulding of the ' pos- terior horn ' is completed by the predominance of the internally protruding wall ( : partie enroulee,' Leuret), to which, now, the term ( hippocampus minor,' or ' pes hippocampi minor,' rightly applies. 1 The fibres of the stem, augmented in number at each accumulation of grey reuniting matter, diverge into and form the main part of the wall in greatest proportion in the Lyen- cepliala. The stem or ' crus ' is formed by the prepyramidal tracts, fig. 66, ]), the olivary tracts f, the teretial and postpyramidal tracts, fig. 49, Y, and so much of the cerebellar tracts, fig. 66, t, as may not have been expended in the formation of the ( nates,' b, ( testes,' n, ( geniculate bodies,' y, and their common basis. Thus the crus or stem of the hemisphere includes tracts of the myelon, connected respectively with the sensory and motory roots of the nerves. The part of the ' crus proseiicephali,' below or in front of the ( locus niger,' consists of white fibres in a coarsely ( fasciculate ' arrangement, fig. 123, d: the part above, derived from the tere- tial, postpyramidal, and cerebellar tracts, is softer, with mixed grey matter, and forms the f tegmentum,' ib. c. The fasciculate fibres, after passing through and being reinforced by the grey matter of the striated body, diverge in curves, fig. 66, c, fig. 122, s, 1 The judicious and painstaking anatomist GRATIOLET seems to have foreseen some late misconceptions of the nature of the hind part of the primitive ventricular cavity in the Quadrumanous brain, in the following note : ' Toutefois, il ne peut etre considere comme un signe A' elevation, car il est beaucoup plus grand en egard a la partie enroulee du ventricule dans les singes, ou son developpement est enorme, que dans I'homme, ou la partie enroulee 1'emporte evidemment sur lui. Cette remarque,' he justly adds, ' est d'une haute importance.' XL", vol. ii. p. 75. PROSENCEPHALON OF MAMMALS. 139 of which many bend downward and outward, suggesting the term ( fibrous ' or e radiated ' cone ; in Man they are traceable chiefly in the sylvian, postsylvian, entosylvian, supersylvian, medilateral, medial, and marginal folds, and into the major part of those of the anterior lobe, fig. 122, a. The tegmental or posterior fibres are, in Man, more directly connected with the transversely arched 122 Dissection of cerebrum and cerebellum, from the outer side, xxxiii". fibres of the great commissure : others, diverging to the posterior lobes, e, b, become connected or continuous with the longitudinal commissural system of the fornix. Figure 123 is a dissection of the inner surface of the hemisphere, c is the section of the corpus callosum, the fibres of which diverge upon the roof of the ventricle, intersecting the radiating fibres, fig. 122, s, and passing into all the folds, which are thus brought into communication with those of the opposite hemisphere. The fibres of the f callosal ' fold, fig. 123, o, o, are chiefly longitudinal, are continued behind, into those of the hippocampus, and in front into those extending from the fornix upon the falcial surface of the anterior lobe : externally 140 ANATOMY OF VERTEBRATES. they form the ( superior longitudinal commissure,' fig. 122, o ; and fibres are traceable from both extremities to the ( perforated space,' figs. 82, 120, x. The dissection, fig. 122, shows also the longitu- dinal fibres extending from the anterior to the inferior and poste- rior lobes, and forming the e external longitudinal commissure,' c, above which are seen part of the radiating fibres, s, interlacing with those of the corpus callosum, c ; which is overarched by the outer- most of the superior longitudinal commissural fibres, o. Above Dissection of the left hemisphere of the brain, from the inner side, xxxni". these are shown the fibres which mainly form the convolutions, but which include not only the ( radiating ' fibres, but those of the f transversely commissural' and 'longitudinally commissural 'kinds: they terminate in or blend with the grey matter which forms the outer crust of the hemisphere. In a section of this substance in a recent brain, a white line is seen to separate it into two layers, as in fig. 124. More closely scrutinised, the following strata have been defined from the surface downward : a thin superficial white layer, a thick reddish grey layer, the intermediate white layer, a thicker grey layer, a third thin white layer, and the deepest grey layer receiving the radiating fibres of the white or medullary cere- bral neurine. 1 1 In the contemporary Reports of my Hunterian Course of Lectures, 1842, the chief conclusions of the comparative anatomy of the superficial grey substance in PKOSENCEPHALON OF MAMMALS. 141 124 Section of grey and white neurine of prosencephalic convolutions. Man. The anterior commissure --the most constant of the trans- verse system is relatively largest in Lyencepliala., figs. 69, 73, c. In the human brain a similar transverse section of it shows its insignificant dimensions, fig. 123, a. Traced trans- versely, in them, it passes, as in a special canal, across the lower part of the corpora striata, bends backward, and expands as it radiates into the middle of each hemi- sphere. It indicates the small part of the human cerebrum which is homolo- gous with the main part of that of birds and marsupials. But the increase of the mammalian over the avian brain begets the added structures for asso- o ciation of added parts, already de- scribed. In Man, each anterior pillar of the fornix, after leaving the ' tha- lamus,' descends and is bent upon itself before ascending, the bend projecting at the base of the brain, behind the ( infundibulum,' as the ' corpus albi- cans,' or e mammillare,' fig. 128, m. In the Lissencephala, where a corpus callosmn is first esta- blished, it might seem, in a dissection from below, that the outer fibres of the ' radiating cone ' curved over the lateral ventricle, and were constricted lengthwise as they ran into each other across the interhemispheral fissure, as in the dissection of the Beaver's brain, fig. 78 : but it is deceptive. There is no actual continuity of any of the ascending radiating fibres of the crus cerebri with those which spread out in transverse curves from the corpus callosum. The two systems are everywhere closely inter- laced; but the fibrous character of the commissural series is lost, mammalian brains was summarised by the Eeporter for the ' Medical Times/ as fol- lows : 'A symmetrical arrangement, more or less regular or complex, can always be traced between the foldings of the two hemispheres, and the more regular in propor- tion to the simplicity of the convolutions : the foldings of the cerebral substance iollow likewise, both in the embryonic development of a complex brain, and in the progressive permanent stages presented by the mammalian series, a regular determi- nate law: some convolutions being more constant than others, and these being trace- able through the greatest number of brains, and recognisable even in the human brain, where, at first sight, they are obscured by so many accessory convolutions.' ' The Lecturer then demonstrated, in a considerable number of prepared brains of different animals, and in a large series of diagrams, in which the corresponding con- volutions in the brains of different animals were marked by the same colours, the facts establishing this important generalisation.' The Medical Times, Nov. 12, 1842, vol. vii. p. 101. Report of 13th Lecture, delivered May 16th, 1842. 142 ANATOMY OF VERTEBRATES. under the microscope, before it quits the ventricular wall to descend, -with the radiating fibres, into the crus. From this stage in the mammalian series the great transverse commissure grows with the growth and complexity of the hemisphere. It consists mainly of white or fibrous neurine, but some grey matter ( f nucleus lcnticularis')is superadded to the inferior fibres external to the radiated cone, and between this and the ' island of Keil ' there is also a thin layer of grey neurine (' nucleus tamire- formis '). Always maintaining its closest connection with the part of the fornix called e lyra,' or hippocampal commissure, whence its development began, the increasing body of transverse fibres extends forward and upward, with a bend or ( genu,' fig. 123, C, O, corresponding in extent with elevation and expansion of the front lobes of the cerebrum. In Man its narrow anterior beginnino; is O o connected by the ( lamina cinerea ' with the optic commissure, receives a small part of the grey substance of the thalamus, and sends off two bands, called ' peduncles of the corpus callosum,' which, diverging, pass backward across the ( perforated space ' to the lower part of the sylvian fold. The corpus callosum, expand- ing as it rises, bends backward, and presents on its upper surface a medial longitudinal groove, called ( raphe,' bounded laterally by the white f strire longitudinales : ' it terminates behind in a slightly down-bent, thickened, free border or ' pad.' Some way in advance of this the attachment of the under surface of the corpus callosum to the fornix begins, and, as the hemispheres increase in the pla- cental series, so does the extent of the filmy inner walls of the lateral ventricles (' septum lucidum,' Anthro.,fig. 123, b) between the body of the fornix and the great superadded transverse com- missure, the fibres of which extend over the roof of those ventricles. The most intelligible illustrations of the comparative anatomy of this interesting part of the cerebral structure is obtained by dis- secting and exposing the lateral ventricle from the outer side, as in the views of the brains of the Opossum, Kangaroo, and Ass, showing the relative proportions of the hippocampus, and of the part of the inner wall distinct therefrom, called ' septum lucidum,' in LXX', pi. vii. In fig. 5, the vascular fold of pia mater called ( choroid plexus ' is shown passing beneath the fore part of the f taenia hippocampi ' through the canal of communication between the lateral ventricles, in both marsupial and placental brains. The supraventricular neurine, being folded upon its stem, the cavity is a reflection of the external surface, and is lined by a continuation of the pia mater, although the fissure by which it SIZE OF BRAIN IN MAMMALIA. 143 enters the ' ventricle ' becomes contracted to a very small extent of the base exterior to the cms. From this point begins the fold extending, as ' choroid plexus,' from one ventricle to the other by the fissure called e foramen Monroianum ' in Anthropotomy. On the interior surface of the hemisphere the pia mater is reduced to an epithelium, the cells of which are less flat in the lateral ven- tricles than in that continuation therefrom called ' third ventricle.' The part of the interhemispheral fissure overarched by the great transverse commissure is the ' fifth ventricle. ' For other dif- ferentiated and definite parts in the archencephalous brain the subjects of the ( bizarre ' nomenclature of Anthropotomy reference may be made to the minute and exact monographs which have been published on that part of the human structure. 209. Size of Brain.- -The brain grows more rapidly than the body, and is larger in proportion thereto at birth than at full growth. But there is a difference in this respect in different Mammalian orders. The brain of the new-born Marsupial is less developed relatively than in higher Mammals, and grows more gradually or equally with the subsequent growth of the body. 1 So, in the degree in which a species retains the immature character of dwarfishness, the brain is relatively larger to the body : it is as 1 to 25 in the pygmy Petaurist, but is as 1 to 800 in the Great Kangaroo ; it is as 1 to 20 in the Harvest Mouse, but is as 1 to 300 in the Capybara ; it is as 1 to 60 in the little two-toed Ant-eater, and is as 1 to 500 in the Great Ant-eater. The brain weighs 6 grains in the Harvest Mouse (Mus messorius), and the same in the Common Mouse (Mus musculus)', but the weight of the Harvest Mouse is 112 grains, whilst that of the Common Mouse is 327 grains. The brain of a Porpoise, 4 feet long, may weigh 1 Ib. avoird. ; that of a Whale (Bal&nopterci) 100 feet in length does not exceed 4 Ibs. avoird. 2 In Artiodactyles the brain of a pygmy Chevrotain ( Tragulus pygm&us) is to the body as 1 to 80; in the Giraffe 3 it is as 1 to 800. In Perissodactyles the brain of the Hyrax is as 1 to 95, whilst that of the Indian Rhinoceros is as 1 to 764. 4 The brain of the Elephant may be three times heavier than that of the Rhinoceros, but a full-grown male would probably weigh down four Rhinoceroses. In Car- nivora the brain of the Weasel is to the body as 1 to 90 ; in the Grisly Bear it is as 1 to 500 ; in Quadrumana the brain of the 1 LXXV', p. 347, pi. vii. figs. 9-12. 2 SCORESBY, in a Balcena mysticetus of 65 feet in length, found the weight of the brain to be 3 Ibs. 12 oz. 8 xcvii-. 4 v". 144 ANATOMY OF VERTEBRATES. Midas Marmoset is to the body as 1 to 20 ; in the Gorilla it is as 1 to 200. But such ratios do not show the grade of cerebral organisation in the Mammalian class: that in the Kangaroo is higher than that in the Bird, though the brain of a Sparrow be much larger in proportional size to the body : and the Kangaroo's brain is superior in superficial folding and extent of grey cerebral surface to that of the Petaurist. The brain of the Elephant bears a less proportion to the body than that of Opossums, Mice, and proboscidian Shrews, but it is more complex in structure, more convolute in surface, and with proportions of pros- to mes-encephalon much more nearly those in the human brain. The like remark applies to all the other instances above cited. The weight of the brain, without its membranes, in a full- grown male Gorilla is 15 oz. avoird. I estimate that of the entire body as being nearly 200 Ibs. : in the relatively larger brains of the small species of Quadrumana the convolutions are feAver, or may be absent, as in Midas. In Man alone is a bulk of body, greater than in any Quadru- mana save Gorilla, associated with a large size as well as with the highest stage of complexity of the cerebral organ. This is, perhaps, the most notable and significant fact in Comparative Anatomy. The weight of the brain in the adult male averages about 49 oz. avoird., and ranges from about 35 oz. to 65 oz. In the adult female the weight of the brain averages about 43 oz. and a half, and ranges from 32 to 54 oz. The mean difference is thus about five ounces and a quarter. The brain has advanced to near its term of size at about ten years, but it does not usu- ally obtain its full development till between twenty and thirty years of age, and undergoes a slight decline in weight in advanced life. 1 The brain, without dura mater, of an Australian female, of 5 feet 3 inches high, weighed 32 oz. ; that of a Bushwoman, 5 feet high, is estimated, in Lin", 2 at 30*75 oz. In European females the brain has been found as low in size ; but the requisite observations to determine the range and the average of cerebral development have hitherto been made only on Europeans. 3 The weight of the brain of the male Hottentot. 3 Ibs. 2 oz. avoird., c3 " dissected by WYMAN/ encourages the expectation of analogous 1 If the capacity of a cranium in cubic inches be ascertained, a fair and instructive notion of the weight of the brain may be obtained by estimating that of a cubic inch of it at 259-57 grains. 2 LVJII '. 3 XLIX", L", LXI". 4 LYIII". MEMBRANES OF BRAIN IN MAMMALIA. 145 results. The human brain is exceeded in weight by that of the Elephant and the Whale, but is absolutely heavier than in all other animals. In the proportionate size of the cerebrum to the cerebellum the human brain surpasses that of all Mammalia : it is as 8 to 1. The brain in some individuals distinguished for intellectual power has been found of unusual size, and remarkable for the number and depth of the cerebral convolutions : the brain of Cuvier weighed upwards of 64 oz. The superficies of the cerebrum of the mathematician Gauss was estimated by "Wagner at 341 square inches, while that of an ordinary wage-man was 291 inches. We know not the size of brain in the Melanian inventor of the ' throwing-stick,' or of that of the deductive observer of the pro- perties of the broken branch bent at the angle of the ( boomerang.' Such benefactors of their race were, perhaps, as superior to ordi- nary Australians in cerebral development, as the analogous rare exceptions in intellectual power have been found to be among Europeans. l 210. Membranes of the Brain. The encephalon, like the myelon, is immediately invested by an areolo-vascular tunic called ' pia mater : ' it adheres to and follows all the foldings of the surface, is continued into the ventricles, and there forms processes called f velum interpositum' and ' choroid plexus.' It is the area on which the vessels undergo the requisite degree of diminution for penetrating the cerebral substance ; and, when with- drawn, the proportion of such vessels pulled out of that substance gives the flocculent appearance of the inner surface of the mem- brane which Anthropotomy calls ( tomentum cerebri.' The movements of the brain are served by a delicate serous sac, called the ( arachnoid.' The outermost membrane, called 6 dura mater,' adheres to the inner surface of the cranium, and consists of a dense inelastic fibrous tissue. It sends a process or duplicature inwards between the cerebrum and cerebellum called ( tentorium,' and a second between the cerebral hemi- spheres called ( falx.' In the Ornithorhynchus a bony plate extends from the cranium into the falx (vol. ii. p. 323, fig. 204, B). A ridge of bone extends a short way into the ten- torium in some marsupials : it is thin in Kangaroos and Phal angers, thick in Thylacines, but of less extent here than in the Wolf, (vol. ii. p. 504). In the Cachalot a bony plate projects from the 1 Tables of size and weight of Mammalian brains will be found in xn, XLI xii". VOL. III. L XXXIl" 14G ANATOMY OF VERTEBRATES. superoccipital into the back part of the falx 1 : the tentorium re- ceives a bony plate in many Delphini. 2 In Seals both the tento- rium and hind part of the falx are ossified, and a thick ridge enters the fore and under part of the falx between the rhinencc- phalic fossa). The tentorium is ossified in the Carnivora to the extent, and in the families, noted in vol. ii., where the conditions of such bony plate are discussed at p. 506. 3 A short tentorial ridge projects anterior to the cerebellar fossa of the petrosal in Lemur macaco.* The tentorial margin of the petrosal is slightly produced in Cebus, and to a greater extent in Aides. In other Quadrumana, as in Man, the sole ossification co-extended with any part of the dura mater is that called * crista galli ' in Anthropo- tomy. An unossified process from the middle of the posterior border of the tentorium, extending from the internal occipital crest, projects into the notch between the hemispheres of the human cerebellum, and is termed ' falx minor ' and f falx cerebelli.' 211. Nerves of Mammals. The olfactory nerves are absent in all the Cetacea save those with baleen, in which they are few and small; they are present in all other Mammals, and are sent oft in greater number from their cerebral centre the rhinencephalon than in lower Vertebrate classes. 5 The Ornithorhynchus is the 1 XLIV. p. 442. Ib. No. 2500, p. 453. 3 A more extensive scries of comparisons of the interior of the skull has tended to rectify the physiological view entertained at the period of the publication of the posthumous edition of the ' Lcgons d' Anatomic Comparee,' of Cuvier, vol. ii. p. 290 ; vol. iii. p. 155. 4 XLIV. p. 722. 5 Anthropotomists still describe the connections and course of the ' crnra rhinen- cephali ' as the origins of the olfactory nerve ; although they recognise that, ' unlike other nerves, a large proportion of grey matter is mixed with the white fibres,' &c. (LXII". vol. ii. p. 583, 186G), and might rectify the notion by many weightier anatomical conditions. Some even maintain the view by such remarks as the following : ' As it is known that in the first development of the ear the peripheral part or vestibular expanse, as well as the rest of the acoustic nerve, is originally formed by the extension of a hollow vesicle from the first or hindmost foetal encephalic compartment, so in the case of the crus cercbri, although the peripheral or distributed part (crus rhinencephali or olfactory nerve) is of separate origin from the hemispheric bulb, this latter part is comparable in its origin with the acoustic vesicle.' I have paraphrased the argument of the editors of LXII" (vol. ii. p. 584), to show that development, as a vesicle in connection with nervous centres, is no ground of homology or homotypy. Whenever a false homology has to be maintained, the earliest and obscurest phenomena of embryonal development are usually resorted to in support of such view. The terminal expansion of the acoustic nerve is in an organ Avhich begins as 'a follicle or hollow vesicle;' the terminal expansion of the optic nerve is also in a vesicle; arid the true olfactory nerves expand terminally on what began as a follicle or vesicle, which form is retained, little altered, in Fishes. The vascular pituitary membrane supporting that expansion is the homotype of the choroid supporting the retina. No doubt the cerebellum is at first a vesicle, as is the optic lobe, and the hemisphere, and the olfactory lobe ; and each may claim to be regarded as the NERVES OF MAMMALIA. 1-17 sole known instance of the olfactory nerve quitting the skull by a single foramen, as in Birds and Lizards (/. e. one from each rhiii- encephalon). In the Echidna the contrast in the vast number of nerves and the concomitant extent of the f cribriform plate ' is extraordinary. Those from the grey tract proceed to ' Jacob- son's organ.' The number of olfactory nerves and extent of the pituitary surface on which they spread is very great in Marsupials. In the Insectivora the Hedgehog is most remarkable in this respect. Both Herbivorous and Carnivorous Gyrencephala have numerous olfactory nerves : some of the Phocidce show this character in excess. The number of the olfactory nerves decreases, with the diminished size of the rhineucephalon, in Quadrumana, up to Man, where they seldom exceed twenty in number, and are least in proportion to the size of the body. They become flattened and expanded where they spread upon the vascular pituitary mem- brane. The optic nerves are smallest in the Moles ( Talpa), largest in the Giraife. They arise from the bigeminal bodies, chiefly from the nates and optic thalami, in Lyencephala and in some Lissence- phala, to which origin are superadded in other Lissencephala and in Gyr- and Archencephala, fibres from the corpora geniculata, along the tract marked d, fig. 68. In the groups in which the eyes are relatively largest, Unyulata and Rodentia, e. y., the larger proportional size of the homologue of the optic lobes, fig. 68, , is significant of its important relationship with the origin of the nerves of vision : the ( thalami ' do not show the like increase ; their larger size in Quadrumana and Bimana relates more to their function as recruiting ganglia of the prosencephalon. The optic nerves, never- theless, seem to be derived more wholly from the ' thalami ' in Man than in most lower Mam- mals, whence the Anthropoto- mical name of those parts. This character is shown in the foetal brain at the fourth month, fig. 125, where c shows the optic tract quitting the thalamus, e the OptlC lobe, J 3 haS not yet origin of optic nerves. Fcetal brain at four months. undergone its subdivision into ( nates and testes.' The liberated nerves bend downward and homotype of the eye-ball, on the ground taken, in LXII" for viewing the olfactory bulbs as nerves, and not as encephalic lobes. The grand old anatomists had truer views of these ' processes of the brain,' as on some other points, than their successor? L 2 14S ANATOMY OF VERTEBRATES. 126 a - Optic cliiasma ; Man. ecu. 127 forward,, converging and meeting beneath the brain at their con- fluence, called ' cliiasma opticum,' a, b. The fasciculi of primitive fibres arc here arranged as shown in fig. 126. The outer ones, b, pass onward to form the outer side of the nerve a, the middle fasciculi cross the cliiasma obliquely, and, after decussating the corresponding fasciculi of the other tract, contribute to the formation of the opposite nerve : the inner fasciculi curve across the back part of the cliiasma, and are continuous with the corresponding fasciculi of the opposite tract, being strictly ( commissural : ' a similar arrangement prevails with a few fasciculi at the fore part of the cliiasma. The hinder commissure is more common, and appears as a little trenial border of the cliiasma, in some Mammals, down to the rodents. Pathology gives evidence of a partial decussation, in some instances, as in the preparation, fig. 127 ; in which the right optic nerve, a, was atrophied ; the left one, by healthy ; with a partially wasted left optic tract, c, while the right, d, retained more of its normal size. 1 The Mammalian chiasma ceases to show the laminated arrangement (vol. ii. p. 122, fig. 47) common in Birds and Reptiles. The nerve, beyond the chiasma, has a strong iieu- rilemma, which sends processes from its inner surface : in some, e. g. Cetacea, converging as lon- gitudinal septa from the circumference to the centre of the nerve ; in most forming longitudinal canals for the neurine, and giving it the character of a cylindrical aggregate of tubes. This is enclosed in a sheath of dura mater, extending to the sclerotic, into which it is partly continued, where the nerve pierces that coat of the eye-ball. Another peculiarity is seen in the small artery running along the centre of the nerve, and ramifying upon its terminal expansion as the f arteria centralis retinas.' Atrophied right optic nerve and tract ; Human, ecu. 1 There have been cases, however, where the tract of the same side as the atrophied nerve showed more wasting than that of the opposite side. NERVES OF MAMMALIA. 14D In some Marsupials the optic nerve grooves the orbito-sphenoid, escaping by a cleft continuous with the fissura lacera anterior 1 : in higher Mammals the nerve escapes by a special ' foramen opticum.' The extra-cranial parts of the nerves are remarkably long in Whales, 2 and in all Cetacea they diverge from the chiasma 1-28 Base of human brain, with origins of nerves ; half natural size. at a wide angle, fig. 60, 2, 2. This becomes less open as the Mammals rise to Man, fio\ 128, b. ? ^5 3 The oculo-motor or 'third' nerve, fig. 60, 3; fig. 128, c, and 1 XLIV. pp. 323, 329. 2 xoiv. p. 387. ]50 ANATOMY OF VERTEBRATES. the * fourth,' fig. 128, c/, have the same origin, distribution, and connections with the sympathetic, as in Man. The branch of the ' third ' nerve, which runs along the lower part of the eye-ball, between the 'inferior' and ' external' rectus muscles, and supplies the ' obliquus inferior,' is connected, usually by a short thick cord, with a ' lenticular ganglion ; ' but this is not so well defined in some Mammals, and the ciliary nerves are usually feAver than in Man. The ( fourth ' nerve supplies the ' obliquus superior ' muscle. In the Sheep this nerve receives some branches from the ophthalmic division of the ( fifth ' nerve. Besides the ( rectus ex- ternus,' the sixth nerve, fig. 128, f, in most Mammals, supplies an additional muscle, the ( retractor oculi.' The ( fifth ' or ( tri- geminal' nerve, fig. 128, e, e', is commonly the largest of the cerebral nerves, and resembles the myelonal nerves, fig. 136, in having a gaiiglionic, fig. 230, 9, 10, and a non-ganglionic, ib. n, portion, the latter being ( motorj,' supplying muscles, the former distributed to sensitive and secerning surfaces. This distinc- tion is better marked in Mammals than in Birds and Reptiles : like which, however, the ganglion is single, not divided, as in most Fishes (vol. i. figs. 201, 202). The size of the 'fifth' nerve relates to the perfection or sensitiveness and application of those surfaces, not to the proportion of the facial to the cranial part of the head. Thus we find the fifth or trigeminal nerve of largest relative size in the Ornithorhynchus paradoxus, which uses, like the duck, its beak as a tactile instrument in the detec- tion of its food. Emerging from the ganglion, fig. 51, o ', anterior to the pons, ib. c, it soon divides into three branches, the first and second appearing as one. The first and smallest division divides into two equal branches : the superior or ethmoidal branch enters the nose, combines, in part, with the olfactory, for the service of the pituitary membrane ; but mainly emerges from the nasal cavity, supplies the skin at the upper part of the face, and, by a branch continued from between the nasal and premaxillary bones, is distributed to the nostrils and contiguous integument. The second division of the fifth is two lines broad and one line and a half thick : after emerging by the foramen rotundum, the chief part of it passes through the ant-orbital canal, and divides into two branches, distributed, the one to the nasal or upper parietes of the face, the other to the lateral or labial integuments. The palatine branch divides into a posterior smaller nerve, which passes through the posterior palatine foramen : the anterior and larger branch emerges from the anterior palatine canal, and supplies Jacobson's organ at the floor of the nose and the palatine membrane. NERVES OF MAMMALIA. 151 The third division of the fifth is broader but thinner than the second ; it leaves the cranium by the foramen ovale, and is distri- buted as usual, mainly to the sensitive labial integument of the lower jaw, fig. 3, , a : its non-ganglionic part goes to the mandu- catory muscles. In the Echidna the triffeminal is of smaller size, and its first O ' and second divisions are much less in proportion to the third, which supplies, from its ganglionic part, the sensitive and secreting surface of the long tongue. This size of the lingual branch of the trigemmal is still more marked in the Pangolins and Ant- o o eaters, especially in Myrmecopliagajubata. A distinct gustatory nerve, communicating with a motory ( facial ' nerve by a ' chorda tympani,' is a mammalian characteristic of the trigeminal. In the Hedgehog the nasal branch is the largest of the first division : after dismissing a few ciliary nerves it quits the orbit and enters its special canal at the fore part of the large cribriform plate, and divides on entering the nasal cavity into the external and septal branches, the latter being the largest, and richly spread upon the pituitary membrane of the septum and inferior turbinal. The 129 Lower jaw of the Porcupine (Ilystrix uristata). bulbs of the vibrissre in the Hedgehog and other Insectivora use a large proportion of the facial branches of the maxillary and man- dibular divisions of the fifth. In Rodents the dental branches of these divisions are large, and especially the nerves sent therefrom to the active and persistent pulps of the scalpriform incisors ; and they show, especially in the mandible, a recurrent course, as I found in the dissection of the Porcupine, fig. 129, *L l The nasal and labial nerves are large in Moles and Shrews, especially the long-snouted kind {Rhynchocyori). But the chief peculiarity of 1 xx. vol. i. p. 103, prep. no. 357B. 152 ANATOMY OF VERTEBRATES. the triovniinal in Talphlcc. is the share which the ophthalmic divi- sion of the 4 fifth ' takes in the function of the reduced eye-ball, as ]1>0 a warner of light. In fig. 130, a is the trige- ininal, b the ganglionic part, c the third or mandibular division, f the second or maxillary division, d the first or ophthalmic division, of which the branch going to the eye, e, is large, while that going to the nose, g, is small, reversing the proportions in the Hedgehog. In many Lisse?icephala the part to which the root of the trigeminal can be traced makes a small prominence on each side the fore end of the ' calamus scriptorius.' In the Elephant the superorbital and superficial nasal branches of the ( first ' division, but more especially the ' facial ' branch of the ( second ' division, which emerges from the antorbital foramen, present a large size in relation to the proboscis. The size of that foramen is not, however, always indicative of that of the nerve. In many Rodentia a part of the masseter traverses, with the antorbital nerve, the foramen in question, which is, then, enormous, as in figs. 234, 238, 241, v (vol. ii. p. 377). The dentary branch of the maxillary exceeds that of the mandibular division of the fifth in the Elephant, to meet the demands of the persistent matrix of the tusk. But this difference in the size of the nerves supplying the upper and lower jaws is maximised in the Balcenidce, in relation to the active and extensive growth of baleen in the upper jaw, and the absence of teeth or their substitutes in the lower jaw. The palatine nerves supplying the baleen-pulps are as thick as the finger in Balana mysticctus. In the Porpoise (Phoccsna) an orbital branch joins a plexus near the fore part of the orifice of the eye-lids, sent off from the ( seventh ' or facial nerve, from which union branches pass to the muscles and membrane of the blow-hole. The maxillary brunch sends off a ( subcutaneus mala?,' which combines with the facial nerves to supply the inferior palpebral muscle, and spread upon the hind part of the palpebral opening. There are five or six antorbital branches which run forward between the maxillary periosteum and the superincumbent muscular and tegumentary layer, emerging to spread upon the latter where it forms the upper lip or margin of the mouth, and also sending a recurrent branch to the blow-hole. A large branch of the maxillary passes Trigcmin.nl nr-rve of Jlole. LX1U". NERVES OF MAMMALIA. 153 through the foramen near the upper opening of the nasal passao-e, and ramifies upon the plicated membranes of the blow-hole. The dental nerves are large from both maxillary and mandibular divisions of the fifth : the gustatory branch is, relatively, small ; and sends off a filamentary ' chorda tympani,' which may be traced to the trunk of the facial, and is connected, in its course, with the carotid plexus of the sympathetic. In Ruminantia the first division of the ( fifth ' subdivides into frontal and nasal : the latter supplies the upper part of the septum and the superior turbinal, and sends a few branches to the fore part of the nose, which meet these filaments reflected from the second division of the fifth. The branches to the lacrymal and harderian glands, to the eyelids, and the larger one which passes out of the orbit to the integuments of the temple, and which chiefly supplies the horn-core, or the growing antler, may be traced back distinctly to the Gasserian ganglion. The second division of the fifth, escaping by the foramen ro- tundum, sends antorbital branches to supply the upper lip, the nostril, and the pituitary membrane at the lower part of the nose. It also sends off the lateral nasal, receiving the ( vidian ' nerve, and supplying the inferior turbinal : lastly, the ( palatine ' and upper dental nerves. The ganglionic part of the third division gives off the ' buccal nerve,' connected with an ' otic ganglion,' supplying the superficial muscles and skin behind the angle of the mouth, and communicating with branches of the 6 seventh ' or facial nerve ; the large branch dividing into the inferior dental and gustatory nerves, the latter receiving the e chorda tympani : ' lastly, the external auricular, passing behind the mandibular ramus, joining the middle branch of the ( seventh,' and supplying the muscles of the ear, but mainly distributed to its sensitive surface. 1 The non-ganglionic part of the fifth supplies the temporal, masseter, and pterygoid muscles, also the mylohyoid and anterior part of the occipito-hyoid or digastric : the part going to the otic ganglion is continued therefrom to the internal pterygoid and to the muscles of the soft palate. A ganglion called ( submaxillary ' and situated near the deeper part of the gland so named, is connected by filaments with the gusta- tory nerve. In Swan's dissection of the cerebral nerves of the jaguar he found the superior nasal sending a branch to join the one from the lenticular ganglion to form ciliary nerves, and then pass forward to send one branch into the nose and another to the skin 1 See dissection of the trigeminal of Bos. in LIV, \>l. xxxii. fig. 3. 1.74 ANATOMY OF VERTEBRATES, 131 :ii the inner angle of the eye. The naso-palatine received the vidiaii nerve, and the { spheno-palatine ' ganglionic enlargement was conspicuous at the junction. 1 The largest portion of the maxillo- dental nerve supplied the great canine tooth. The gustatory nerve gave a branch to the lining membrane of the mouth and passed forward dividing into branches which communicated with the 6 ninth ' in their course to the surface of the tongue. Such Quadrumana as have been dissected with this view show all the main characters, connections, and accessory ganglions, of the fifth, which are so fully described in late works on the anatomy of Man. The apparent origin or place of emergence of the fifth nerve is at the middle ' crus ' of the cerebellum, fig. 128, . SWAN also ?hows it in the calf, pi. xxxvi. fig. 3, 11. ALCOCK found the spheno-palatine ganglion in a rabbit, dog and horse, as well as in ihe eat and cow. CCYIII. p. 28G. Macromyelon and origin of thttmi nerve, Man; natural size, ocvui. NERVES OF MAMMALIA. 155 olfactory : ( the other nerves of this part, derived from other origins, only conveying common sensation.' ' It is upon this principle the fifth pair of nerves may be supposed to supply the eye and nose in common with other parts, and upon the same principle it is more than probable, that every nerve so affected as to communicate sensation, in whatever part of the nerve the im- pression is made, always gives the same sensation as if affected at the common seat of sensation of that particular nerve,' ib. p. 190. 1 The nerve which is homologous with the e ramus opercularis sen facialis,' and some other branches of the non-ganglionic part of the ' fifth,' in Fishes (vol. i. p. 303), is more distinct in its origin, at least its apparent one, in Mammals, and is reckoned in Anthropotomy as a separate cerebral nerve, under the name of 6 facial,' or as a part, e portio dura,' of the ( seventh pair,' with which it has less real relation or connection than with the fifth. It is essentially the complementary proportion of the motory or non-ganglionic part of that great myelonal nerve of the head. In fig. 131 is shown the point, behind the olivary tract, where the facial, 16, diverges from the smaller portion of the motor division accompanying the sensory division of the trigeminal : its angle of divergence is wide, and its place of emergence is behind the c pons,' close to that of the acoustic nerve, fig. 128, y. It enters, therewith, the internal auditory foramen, leaves the acoustic to enter its own canal in the petrosal, called ( aqueduct of Fallopius ' in Anthropotomy, passes downward behind the tympanic bone (as in Birds), and emerges by a foramen called ( stylo-mastoid.' The facial nerve supplies the muscles of the mouth, nose, eyelids, ear-conchs, and the cutaneous muscles of the head and beginning of the neck. In the Porpoise, the facial nerve, on quitting the petrosal, gives small branches to the cutaneous muscular layer of the ear-opening and parts behind, communicating; with filaments of the cervical nerves : a branch o ramifies on the mylohyoid muscle. From the trunk of the facial a slender nerve passes to above the mandibular joint, then bends forward, enters into, and receives a filament from, a sympathetic plexus, and quits it to join the third division of the fifth : this answers to the f chorda tympani.' The trunk of the facial is, 1 One of the observations and experiments on which Hunter founded this conclu- sion, is given, in Latin, by Sir C. Bell, in his original Essay, LXIV", p. 11 (1811). So, also, Sir Charles writes: ' The key to the natural system of the nerves will be found in the simple proposit'on, that each filament or tract of nervous matter has its pecu- l ; ar endowments independently of the others which are bound up along with it, and that it continues to have the same endowment throughout its whole length.' LXV", p. 70. 156 ANATOMY OF VERTEBRATES. then, continued forward, superficially, along the slender jugal bone, toward the eye-opening, supplies the ' angularis oculi pos- ticus,' and the muscles of the under eyelid : in advance of this it supplies the ( angularis oculi externus,' and forms a large plexus, in connection with branches of the trigeminal. From the plexus pass filaments to the muscles of the blow-hole and its plicated sacs. In Mammals with a well developed parotid the facial traverses that gland; it divides there into three principal branches in the Calf 1 and Dog; 2 whilst in the Hog, the trunk is continued forward to near the fore part of the masseter, before dividing into maxillary and mandibular portions, and the auriculo-palpebral branches come off more separately from the long trunk. In Quadrumana, as in Man, the chief branching of the trunk takes place at the hind margin of the masseter after the post-auricular nerve is sent off: from the upper of the main divisions pass the nerves to the temple and eyelids as well as to the nose and upper lip. A slight enlargement of the facial near its entry into the e fallopian aqueduct '- -its petrosal canal is called f geniculate a-ano-lion ' which receives a petrosal branch of the vidian nerve, and one from the superficial petrosal which unites the otic gan- glion with the tympanic nerve. Prior to the ganglion the facial is connected by one or two filaments with the acoustic nerve : be- yond the ganglion it receives a petrosal filament of the sympathetic. The ' chorda tympani,' fig. 259, c, leaves the trunk of the facial before it quits its canal, enters the tympanum, crossing the tym- panic bone and the ear-drum, behind the handle of the malleus, b, to emerge by an aperture at the inner end of the ' glaserian fissure:' then passing downward and forward it joins the gusta- tory. In the Horse and Calf I traced, in 1836, 3 the superficial petrosal branch, or backward continuation of the vidian nerve, fig. 132, li, into the seventh, penetrating its sheath, but remaining distinct, and separating into many filaments, ib. b, with which filaments of the seventh nerve, ib. b, k,f, are blended, and a ganglion formed, ib. ^7, by the superaddition of grey matter ; the chorda tympani, ib. m, is here continued partly from this ganglion, partly from the seventh or portio dura, ib. 6. I did not at that time distinguish the fasciculus, b, called ( portio intermedia ' of the facial from the main trunk, a. The chief point, however, as to the ( chorda tympani' not being a branch of that main trunk 1 LIV. pi. xxx. fig. 3. 2 Ib. fig. 2. 3 In reference to the expression of Hunter, relative to the chorda tympani, ' I am almost certain it is not a branch of the seventh pair of nerves, but the last described branch from the fifth pair.' xciv. (1837) p. 194, and ' Note a.' NERVES OF MAMMALIA. 157 liiagraui of the ' portio intermedia,' with the ganglionic origin of the ' chorda tympaui.' LXXII". of the facial, receives corroboration from the special researches of Morganti l into this intricate and difficult part of neurotomy. In the subjoined diagram of the 132 result of his dissections, fig. 132, the portio intermedia, b, is separated from the vestibular division of the acoustic c, and from the main trunk of the facial , with both of which it lies in close contact. The filament d connects b with c, and receives one from the latter. Two filaments e connect the ( intermediate ' with the main portion of the facial, a. The intermediate portion is resolved into filaments, b, before joining the ganglion, y, the nature of the f grey or ash-coloured tissue ' of which has been established by the microscopic demonstration of the ( ganglion-corpuscles ' (LXVI", p. 549). With this ganglion are connected the superficial petrosal branch of the vidian, h, from the spheno-palatine ganglion, and the smaller 133 nerve, i, from the f otic ganglion : ' filaments k, /, from the facial, , and the chorda tympani, m. Morganti, however, traces a filament n to that nerve directly from the facial. In the Sheep, fig. 133, the ' portio inter- media ' b, is more closely connected, by d, with the acoustic nerve, c ; and sends a shorter and thicker division to the ( geniculate ' ganglion c/, by which it is more directly continued into the ' vidian ' branch e ; the ' chorda tympani,' f, being continued mainly from the ganglion, but also, in a smaller degree from the facial, a. The branch from the ' portio intermedia,' b, I described as the ' vidian ' crossing the ' portio dura,' a. The acoustic nerve, fig. 131, is, rises from the floor of the fourth ventricle, chiefly in connection with grey matter consti- tutino' the ' acoustic nucleus.' The nerve consists of an anterior o and posterior portion the course of which is more oblique in Man than in most Mammals owing to the great thickness of the cere- bellar crus, ib. 7. In the Cat the posterior root is very large, is a thickened band of fibre from the fusiform cells of the posterior portion of the nucleus; the band passes along the floor of the Relations of the chorda tympani and vidian nerve to tho 'seventh' nerve Sheep, magnified two dia meters. LXVI". LXX". 168 ANATOMY OF VERTEBRATES. fourth ventricle, joining fasciculi from the cerebellar cms and those of the anterior root. This ' consists of two portions, of which the chief penetrates the medulla beneath the restiform body and enters both parts of the acoustic nucleus : the other portion runs backward along the upper border of the restiform body, which it accompanies over the superior peduncle to the inferior vermiform process of the cerebellum.' 1 The ( flocculus,' fig. 64, ?z, with which the acoustic nucleus is connected, is large in the Cat, the Aye-aye, the timid Rodents, and all the small Mammals with acute hearing ; it is relatively small in the Sheep and most Ungulates. The acoustic nerve quits its origin in contact with the facial, fig. 128,^7, a small artery to the labyrinth runs between them: it takes a short course to the ( meatus internus,' longer in Cetacea than in other Mammals, receives a filament or two from the intermediate part of the facial, figs. 132, 133, d, on entering the meatus, and then divides. The part penetrating the fore half of the cribriform plate supplies the cochlea ; its large size is a mam- malian characteristic, and is most remarkable in the Cetacea : the posterior division, answering to the main part of the acoustic in lower Vertebrates, is spent upon the vestibule and semicircular canals. The eighth cerebral nerve, in anthropotomical enumeration, includes the three nerves called f glosso-pharyngeal,' ' vagal,' fig. 128, h, and ' spinal accessory/ ib. /. The roots of the glosso- pharyngeal are traceable to a nucleus of grey matter at n, fig, 57. The vagal nuclei, ib. h, are forward (in Man upward) extensions of the grey or vesicular myelonal columns from which the spinal accessory rises : they lie on each side of the hypoglossal nuclei, ib. g, on the floor of the fourth ventricle, but are united by the commissure forming the roof of the central canal before this opens into the ventricle : higher up the vagal roots penetrate the ' caput cornu,' like the posterior or dorsal myelonal roots. There is a partial decussation at the raphe. Both glosso-pharyngeal and vagal nerves emerge at the angle between the olivary and restiform tracts of the macromyelon, k, k, fig. 57, and are soon joined by the aggregate of the roots of the ( spinal accessory : ' these, commencing at about the fifth cer- vical, advance, between the dorsal roots of the cervical nerves and the ligamentum denticulatum, gathering successive slender accessions, all of which, originating as above defined, emerge at the dorsal border of the restiform tract. The glosso-pharyngeal is relatively smaller in Mammals than 1 xx". NERVES OF MAMMALIA. 159 134 in Birds (vol. ii. p. 124), is mainly distributed to the back part of the tongue and to the pharynx in all Mammals ; passing thence to the ' flocculus ' in its way to the jugular foramen, it retains its proper fibrous sheath, and usually presents the two enlargements called 'jugular' and ' petrous ' ganglions, before emerging from the skull. From the petrous ganglion a filament enters the tympanum, where it joins a plexus from the sympathetic, and supplies the membrane continued into the eustachian tube. The pharyngeal branches are joined by filaments from the vagus and sympathetic to form the pharyngeal plexus. Filaments are sent to the tonsils and fore part of the epiglottis ; those to the tongue supply the muscles at its base and the mucous membrane covering the base and sides of the tongue, some filaments terminating in the fossulate papilla?. In the Porpoise the glosso-pharyngeal divides at its exit from the skull into a smaller and larger branch. The former is dis- tributed to the sphincter of the lower or palatal part of the nasal canal, and unites there in a plexiform way with a branch of the vagus. The larger division supplies the palate and base of the tongue, and the muscles between the pyramidal larynx and the hyoid. Some filaments pass to the anterior ganglion of the sympathetic. The glosso-pharyngeal is fi- gured, in LIV. pi. xxxi. fig. 2, 9, and pi. xxxii. fig. 3, 22 (Uos), showing its communications with the e vagus ' and sympa- thetic ; also ib. ib. fig. 3, 1.3 (Felis) showing connections with the gustatory branch of /?, the trigeminal. In fig. 134, from the human subject, the emergence of the glosso-pha- ryngeal, 4, from the post-pyra- midal, c, and post-myelonal, y, tracts is shown at 2 : the petro- sal o*ano'lion and connecting o o o filaments with that of the upper vagal ganglion at 8 and 10 : 7 is the auricular branch of the vagus, 9 the 'ramus anastomo- ticus ' of Jacobson, 13 the trunk of the glosso-pharyngeal. The vagus, fig. 134, 3, or ' pueumogastric ' from the important Origins and connections of the constituents of the ' eighth' or pneumogastric nerve, Man. LXVII". ICO ANATOMY OF VERTEBRATES. organs the lungs and stomach which it supplies, sends branches ^^ ^5 * J- also to the larynx, trachea, and heart. As in other Vertebrates, it has the longest course, widest distribution, and most numerous connections, of any of the cerebral nerves; but is noted, in Mam- mals, by receiving the accessory nerve, ib. 5, 11,12, from a greater extent of the myelon : the recurrent branches of the vagus are more exclusively distributed to the trachea and larynx, and send a smaller supply of nerves to the rcsophagus than in Birds or Reptiles. From the remarkable length of the neck of the Giraffe, the condition of the recurrent nerves attracted my attention in dis- secting that animal : they were readily distinguishable at the upper third of the trachea, but when sought for at their usual origin, this was less obvious. Each nerve was not due. as in the & ~ ' short-necked Mammals, to a single branch given off from the vagus, continued of uniform diameter round the contiguous great vessel and throughout their recurrent course, but it received several small filaments derived from the trunk of the vagus at o different parts of its course along the neck. 1 Branches of the superior laryngeal nerve directly perforated, as in some other quadrupeds and in the Porpoise, the thyroid cartilage, and were joined, in a greater proportion than in Man, by branches of the recurrent, before distribution to the laryngeal muscles, of which, however, the crico-thyroid owes its supply chiefly to the upper laryngeal and the rest to the recurrents. In Quadrumana, as in Man, the internal laryngeal perforates the thyrohyoid membrane at the interval between the hyoid bone and thyroid cartilage. The upper laryngeal is proportionally larger in the Orang, Chimpanzee, and Gorilla, and mainly supplies the capacious laryngeal sac in those apes. In the Porpoise the left recurrent winds round the end of the arch of the aorta, near the remains of the ductus arteriosus ; the right recurrent winds round the subclavian immediately before the origin of the posterior thoracic : both recurrents send filaments to the oesophageal plexus from the sympathetic on their forward course to the larynx. After the origin of the recurrents, the vagal trunk sends off the cardiac branch, which, unitino- with c5 sympathetic filaments, forms the plexus supplying the heart. Next are sent off the nerves to the bronchial plexuses ; finally the vagal trunks pass with the rcsophagus through the diaphragm, the left on the ventral, the right on the dorsal side, and combine 1 xcvn'. NERVES OF MAMMALIA. 161 with branches from the sympathetic to supply the complex stomach and the numerous spleens. Most Mammals exhibit the grey enlargement of the vagus after its exit from the jugular foramen, but less distinctly divided into an upper, fig. 134, 6, and lower, ib. is, ganglion, than in Man. The principal branches e.g. 7, auricular; 10, interganglionic; 15, pharyngeal, deriving one filament, 16, from the vagus, the other, 17, from the ( spinal accessory ; ' 19, 20, superior laryngeal, the re- current, cardiac, pulmonary, oesophageal, and gastric are the same as in Man, likewise their connections with contiguous o nerves, and especially, as by the l filaments,' 21, 22, with the upper sympathetic ganglion. The spinal accessory, besides its portion, ib. 11, blending with the trunk of the vagus, distributes branches to the trapezius, masto-humeralis, and sterno-maxillaris, in Ungulates ; to the cleido-cucullaris and cleido-mastoideus, in Carnivores ; and to the trapezius and sternomastoid in Quadrumanes and Man. The condition of existence of a spinal accessory is not the extension of muscles from the skull to the thorax for the acts of respiration, but the general homology of the scapular arch as the haemal one of the occiput : accordingly the nerve is found in all Vertebrates ! ; and only when the development of the appendage of that arch calls for its displacement, and attracts for the manifold motive and sensitive requirements of the limb, successive nerve-bundles from the part of the myeloii co-elongating with the neck, are the root-filaments of the ' accessory ' drawn down beyond their normal, intercranial, place of origin, as at 5, 5, fig. 134. The macromyelonal, by some called ( respiratory,' centres, to which the origins of the several divisions of the ' eighth pair ' have been traced, are connected by means of longitudinal fasciculi and cell-columns, continuous with those in the cervico-dorsal regions of the myelon, with the trigeminal nerves, and with both anterior (lower and middle roots of the ' accessory') and posterior cornua of the myelonal grey matter, fig. 40, g, h : thus minis- tering to a series of motions, both direct and reflex, of high importance. The roots of the ninth or hypoglossal nerve may be traced to groups of nerve-cells in front of the central canal, ib. b, just above the upper cervical nerves, apparently a continuation of the cell-columns from which the ventral or motor roots of the spinal nerves arise : some of the roots decussate at the raphe, but most 1 For the homologue of this nerve, see, in Fishes, vol. i. p. 307 ; in lieptilcs, ib. p. 313 ; in Birds, vol. ii. p. 125. VOL. III. M 1G2 ANATOMY OF VERTEBBATES. of them sink deep into the nucleus. They are connected with each other, with the roots of the vagus, and with those of the spinal accessory by means of large multipolar cells. In the Giraffe the lower roots emerge, like a small ( accessory,' from the cervical part of the myelon. The main roots of each hypoglossal quit the macromyelon, be- tween the prcpyramid and olive, figs. 81, 82, 9, usually in two bundles, which escape, in many Marsupials, by two precondyloid foramina : but in most Mammals the bundles, perforating sepa- rately the dura-mater, pass out by a single precondyloid foramen, and then unite. The nerve is closely connected with the vagus, and contiguous cervical ganglion of the sympathetic, passes between the carotid and jugular, then forward between the basi- hyal and hyoglossus, and is continued into the substance of the geniohyoglossus beneath the tongue to its tip. In the Porpoise a small branch of the ( ninth ' is distributed to the sphincter muscle of the posterior nostril, before the supply to the muscles of the hyoid and tongue is sent off from the main part of the nerve-trunk, which is relatively small in Delphinidcs. In the Giraffe the motor nerve of the tongue is larger in proportion to the body than in the Ox : it is largest in the Pangolins and Anteaters, in relation to the great length of the tongue, and frequency and extent of its muscular motions. As the size of the ( ninth ' governs that of its special outlet from the skull, the precondyloid foramen indicates that the great ex- tinct tree-uprooting Sloths (Mylodon, Megatherium} applied a long flexible prehensile tongue to the plucking off the branches of their prostrated aliment, in a greater degree, even, than is now witnessed in the Giraffe. 1 Among the connections of the ninth are some with branches of the superior laryngeal to the sterno-hyoid and sterno-thyroid, associating the movements of the tongue with those of the larynx. 2 In Quadrumana the cervical branch assumes more the characters of the ( descendens noiii ' of Anthropotomy, and supplies the additional differentiated muscles of the hyoid. The ninth, like the ' accessory,' is essentially a motor nerve, and I have not seen a distinct ganglionic or dorsal root in any Mammal. The last, lowest, or hindmost, of the motory nerves of the head is that which supplies the muscles of the occipital or fourth haemal, or scapular, arch; and the origins of which, fig. 134, 5, 5, in the course of growth of the neck and cervical part of the 1 For the light which may be derived from both nervous and arterial foramina in the interpretation of fossil bones, see xcv', pp. 37, 57, pis. vi. vii. xvi. fig. 2, c. 2 A good view of the distribution of the ' ninth' in the Jaguar is given in LIV, pi. xxxi. fig. 3, 19, NERVES OF MAMMALIA. 163 myelon are drawn down beyond the cranium. In the Vertebrates, retaining the typical connections of the arch, the homologue of the s spinal accessory ' retains its cranial place of origin, as well as the connections with the ganglionic or sensory part of the nerve. The next cranio-motory nerve, in advance, is that which supplies the muscles of the parietal or third haemal, or hyoidean, arch. Both ninth and spinal accessory have their ganglionic or sensory complement in the f vagus : ' and, with reference to the place of origin of that nerve, it may be remembered that both heart and breathing organs belong to the head in Fishes, The second, or frontal, or mandibular, haemal arch has its gan- glionic nerves from the third division of the fifth, its non-o-anglionic 7 C3 C5 by that part of the trigeminal supplemented by certain branches of the e facial.' The rest of the facial represents the motory por- tion, as the first and second divisions of the ganglionic part of the fifth are the sensory portions of the nerve of the nasal or maxillary haiinal arch and its clothing. The ( sixth,' ( fourth,' and ( third ' are parts of the cranial motory nerve-system applied to a special organ of sense. The myelonal nerves indicate the segments of the axis enclosed in their protecting vertebral rings : both segments and nerve- pairs being called into being according to the requirements of the trunk and limbs of the species. The head-segments and trunk-segments directly succeed each other in Protopteri and Teleostomi (vol. i. pp. 7, 14) ; but in Mammals, as in other air- breathing Vertebrates, neck-segments and nerves are interposed ; and, as the scapular appendage becomes developed into a jointed limb, requiring a more backward position, through its size, or one of more freedom for the exercise of various movements, it attracts, as it were, the requisite nerve-force from the successive points or segments of the myelon, and chiefly from a post-cranial or cer- vical portion. The development of nerves, as of vessels, is not primary and independent, but secondary and subordinate to the parts needing them. If the appendage of a haemal arch retain its archetypal simplicity, as in Protopterus (vol. i. p. 163, fig. 101), one pair of nerves serves it : if it grows to a maximum of size and number of digital divisions, it may attract its nerve-supply from fifty successive segments of the myelon (LIY. pi. xi. Raia batis). In Mammals eight or nine segments succeeding the encephalon minister nervous power to the scapular arch and its appendage, the latter chiefly drawing upon the last three, four, or five pairs, which are proportionally large. M 2 164 ANATOMY OF VERTEBRATES. Because the neural arch and corresponding muscular segment have conditioned the beginning of the corresponding pair of spinal nerves, it does not follow that the specially enlarged and endowed appendage of such segment is arche typically an aggre- gate of as many appendages as the nerve-pairs from which it has attracted branches in the course of its growth and development. But, on this assumption have rested the conclusions that the scapula was an aggregate of all the cervical pleurapophyses, and that the humcrus was the coalescence of the five diverging appendages retaining their primitive and typical freedom in the five digits : and,, by parity of reasoning, the scapula of the Skate should be an aggregate of more than fifty pleurapophyses, &c. I assume that anatomists are agreed that the bone, vol. i. fig. 101, B, 51, is the homologue of 51, in fig. 101, A: that the scapula of the Amphiuma answers to the bone so called in other Reptiles and in Birds : and that the occipitally attached scapula of the Lepidosiren is the homologue of the similarly named and con- nected bone in other Fishes. But the long cylindrical rib-like ' scapula ' of the Lepidosiren is one element, and the diverging segmented appendage of the scapular arch manifests the like essential unity. Now, the bifurcation of the distal segment of the homologous diverging appendage in Amphiuma does not make the unsplit part (fig. 101, B. 53) an aggregate of two appendages, nor its scapula, ib. si, an aggregate of two ribs. And the same may be predicated of five or any greater number of radiated divisions of the terminal part of the scapular appendage. But the pectoral fin of the Skate is the pectoral filament of the Mud- fish, the fore-leg of the Quadruped, the wing of the Bird, the arm and hand of Man : i. e. they are homologous parts though with a supply of muscles, nerves, and vessels, according to their respec- tive sizes, shapes, and uses. Say that the appendage in Lepidosiren, fig. 101, A, 53-57, is a dermal development, and that the humcrus, radius, &c. in its higher homologues, are skin-bones, and not parts of the endo-skeleton : it does not follow that the scapular arch, ib. 51, 52, is, also, part of the dermo-skeleton. What, then, is it? This question I propounded, in 1846, l in reference to all the parts of the vertebrate skeleton of which anatomists were at one in respect to their special homology : it applies to the basi- occipital (vol. i. fig. 77, i) and other elements of the occiput of the Fish, as well as to the scapular arch therewith connected. What is the basioccipital ? Anatomists are agreed that the ' basilar process of the occipital bone' (Anthropotomy) is its homologue: in 1 LXXIV, p. 276. NERVES OF MAMMALIA. 165 other words, that the same bone or osseous element may be pointed out from the Cod-fish up to Man. But at this point the above question may be met by the averment, that it need not be asked : that there is no ground for homological generalisation higher than the special one. Such anatomists rest on the step beyond which Cuvier refused to pass. With him parts were homologous because they served similar purposes, or were under like teleo- logical conditions of existence. Neither the final nor the me- chanical causes of separate basi-, ex-, and super-occipitals, of basi- and ali-sphenoids, parietals, &c. in the skull of the foetal Bird or Kangaroo, have been explained l ; and as I am unable to conceive of them, and am in 110 wise helped by the averment of inhe- ritance, I retain my conviction that the basilar process of the human occipital bone is the centrum of the hindmost cranial ver- tebra ; having, moreover, traced the scapular arch and appendage to its extreme of simplicity in Protopterus and Lepidosiren, I accept the light which such condition throws upon its general ho- mology, as the hasmal arch of the same (occipital) cranial vertebra. If there be cartilaginous fishes that combine a foetal gristly con- dition of skull with a maximised development of scapular append- age, I conclude that the backward displacement of the sustaining arch, from its type-position, is a consequence of such development, and prefer to allow my reasoning as to the nature of a limb to be guided by the state and conditions of such appendage in the verte- brate series, rather than by the state of the cranium in one part thereof. It is not probable that the pectoral fin of Shark or Skate shows the condition under which the appendage of the scapular arch first appeared in fishes. 2 On laying open the neural canal, and exposing the myelon by slitting up and reflecting the ' dura-mater,' as in fig. 135, the roots of the nerves are seen, which go off in lateral pairs, and escape at the intervals of the vertebras: they are called the ( spinal' or ' myeloual' nerves. One bundle of the radical filaments proceed from the antero-lateral, the other bundle from the postero-lateral 1 Messrs. Seeley and Spencer dispute the priority of such explanation and don't give it. xci" and xcn." 2 Respect for the conductors and editor of LXXV has led me into the above digres- sion; and as they meet what they consider the 'main defect ' (ib. p. 123) of the present work by an ' argumentum ad verecundiam,' I would observe that the individual who first perceives, or discovers, the general homology of the basioccipitil, the scapula, or other part of the hindmost segment of the skull of a cod-fish, puts himself in advance of, and more or less in antagonism with, others. If his perception be true, but not accepted, it is not his fault that ' he be right and everybody else wrong.' -Such a state of things has happened more than once in the history of science, but it is happily transitory; the many moving one-ward, the one onward. 1G6 ANATOMY OF VERTEBRATES. 135 fissure, and between the bundles passes a delicate fold of the arach- noid, which is attached by an angular process, d, to the dura-mater at the interval, usually, of each nerve (p. 7 8), The anterior or ventral and the posterior or dorsal bundles converge, separately per- forate the dura-mater, and unite, at the in- ter vertebral foramen, into a single ( nerve.' In the Elephant the posterior roots come off abruptly in a few, large, and distinct bundles : the anterior roots emerge from a longer extent of their furrow, are nume- rous and small, and form several bundles before passing through the dura-mater. The same characters of the anterior and posterior origins are seen in Cetacea, in which the two roots preserve their distinct course before uniting, after perforating the dura-mater, longer than in other Mam- mals. In the human subject, especially at the cervical part of the myelon, the anterior root, fig. 136, A, is the small- est ; its finer fila- ments form more delicate fasciculi, aggregating into two, before uniting, as a flat band, with the posterior root. Of this the fila- ments, P, are larger, and blend with the cell-substance of a ganglion, G, before uniting with the anterior root to form the nerve-trunk, c. The capital experiment which has immortalised the name of CHARLES BELL was suggested by the above anatomical fact, and I quote his original account of it from the extremely rare little tract, which he printed for private distribution in 18 II. 1 1 LXIV. Portion of myelon, with roots of nerves of one side. Human, natural size. Roots of myelouaJ uerve, magn. NERVES OF MAMMALIA. 167 Believing that he could f trace down the crura of the cerebrum O into the anterior fasciculus of the spinal marrow, and the crura of the cerebellum into the posterior fasciculus, I thought/ he writes, p. 21, ( that here I might have an opportunity of touch- ing the cerebellum, as it were, through the posterior portion of the spinal marrow, and the cerebrum by the anterior portion. To this end I made experiments which, though they were not conclusive, encouraged me in the view I had taken.' ' I found that injury done to the anterior portion of the spinal marrow convulsed the animal more certainly than injury done to the posterior portion, but found it difficult to make the experi- ment without injuring both portions.' ( Kext considering that the spinal nerves have a double root, and being of opinion that the properties of the nerves are derived from their connections with the parts of the brain, I thought that I had an opportunity of putting my opinion to the test of experi- ment, and of proving at the same time that nerves of different endowments were in the same cord, and held together by the same sheath. ' On laying bare the roots of the spinal nerves, I found that I could cut across the posterior fasciculus of nerves, which took its origin from the posterior portion of the spinal marrow, without convulsing the muscles of the back ; but that on touching the anterior fasciculus with the point of the knife, the muscles of the back were immediately convulsed' (ib. p. 22). The ventral as well as the dorsal roots of the spinal nerves are traceable to the contiguous parts of the grey tract, the latter more immediately, as at k, fig. 40. They are severally connected with, but do not constitute, the white columns from which they emerge. Comparative anatomy testifies plainly against the anterior and posterior columns being aggregates and brainward continuations of the motory and sensory roots. Thus, in the instance of such unusual elongating growth of the myelon as takes place in the neck of the foetus of the Giraffe, as many of the roots of a nerve, the origin of which may be so extended by interstitial myelonal increase, incline tailward as head ward (p. 75). And accurate experiment gives the same response, sensation continuing or being heightened in parts supplied by nerves beyond the place of the myelon of which the dorsal or posterior columns have been divided. The most constant anatomical concurrence with sensory func- tion is the ganglion, fig. 136, G, fig. 131, 9. In all Mammals the trunk, fig. 136, C, formed by the union of the two roots soon divides into an anterior and a posterior pri- 168 ANATOMY OF VERTEBRATES. inary set of nerves. The posterior or dorsal are usually the smaller division, and, bending backward, soon subdivide into external and internal branches. The pairs of nerves are classified, according to the regions of the vertebral column where they emerge, into ' cervical,' ' dorsal,' * lumbar,' ' sacral,' 6 caudal,' and offer numerical differences corresponding with those of the verte- bras, in the Mammalian series. Each is anterior to the correspond- ing bony segment, and, for the most part, escapes between that and the segment in advance ; but the notch of the ( conjugational foramen ' is always deepest at the fore part of the neurapophysis answering to the nerve, and is directly perforated thereby in many instances ; as, e. g. that of the atlas by the first cervical in the Tapir, 1 and also that of the axis by the second cervical in the Hyrax. 2 Most of the cervical and the dorsal vertebrae are perforated by their corresponding nerves in the Hog and Pec- cari ; 3 and some dorsals and lumbars are so perforated in most Ruminants. 4 Therefore, I count the ( suboccipital ' nerve as the first cervical one, and reckon the f eighth cervical ' of Anthropo- tomy as the f first dorsal.' Some details of the distribution of the myelonal nerves in Monotremata are given in LXXXI*. In the Cetacea they have been described by Stannius 5 and Swan 6 in Phoc&na communis. In the Porpoise, the first cervical has a distinct posterior root, smaller than the anterior one, but with a small ganglion ; be- yond which the two unite, as usual. The posterior or dorsal branches supply the occipital and contiguous integument, and the tegumentary and other muscles passing to the occiput ; supplying, also, small branches to the f masto-humeralis.' The anterior or ventral branch passes along the scalenus, joins cor- responding branches from the second and third cervicals, and, in combination with the f descendens noni,' supplies the sterno- hyoid and sterno-thyroid muscles. The second and succeeding cervical nerves are larger. A posterior branch of the second perforates the masto-humeralis, and supplies the integument of the neck. Other posterior branches of this and following cer- vicals supply the interspinales, spinalis cervicis, splenius capitis, and the more superficial muscles and integument at the fore and dorsal parts of the trunk : ventral branches go to the scalenus anticus, levator anguli scapula?, and contiguous muscles. The fourth cervical contributes the largest part of the ( phrenic nerve,' but it receives a filament from the third cervical, sometimes from the second ; always from the fifth. The left phrenic passes a 1 XLIV, p. 501. 2 Ib. p. 522. 3 Ib. pp. 543, 563. 4 Ib. p. 579. 5 Lxxvr-. LIT, 2d ed. p. 156. NERVES OF MAMMALIA. 169 short way along the scalenus anticus ; as it sinks deeper, it gives a filament to the pectoralis major, passes over the aortic arch and trunk of the vagus in entering the thorax, passes along the anterior mediastinum, and then along the pericardium to the left side of the diaphragm. The right phrenic crosses the subclavian, or trunk of the brachial artery, in entering the thorax, and supplies the right half of the diaphragm. A small branch of the anterior division of the fifth cervical, a large branch of that of the sixth, a still larger one of the seventh, and a smaller contribution from the first and second dorsal nerves combine to form the axillary plexus, prior to which are sent off nerves to the scalenus anticus, subscapularis, teres major, and latissimus dorsi. From the plexus is continued a branch beneath the triceps, which quickly radiates small filaments, one of the largest of which is continued along between the radius and ulna ; a second branch passes along the inner side of the triceps to the olecranon ; a third branch goes between the hind border of the scapula and the triceps outward and forward, it supplies the infraspinatus and deltoid, and ends in the periosteum and skin at the fore part of the humerus. Many small twigs are sent to the subscapularis muscle. The hindmost and strongest branch goes obliquely outward and backward, giving filaments to the latis- simus dorsi, and bends over the chest to the sternum, along the side of which it distributes itself to the serratus magnus and con- tiguous muscles attached to the ribs ; it answers to the ( external o thoracic nerve.' There are thirteen pairs of dorsal nerves, each dividing into a dorsal and intercostal part. The dorsal division bends over the rib-neck in the anterior vertebras, and over the lengthening diapophysis in the posterior ones, and subdivides into a superficial and deep part ; the latter supplies the spinales, interspinales, and the fascia of the muscles of the back ; the superficial nerves contribute to the longissimus dorsi, and levatores costarum, in their way to the skin of the back and its muscles. The ventral divisions of these nerves are less distinctly subdivided into external and internal fasciculi than in quadru- peds. The first intercostal sends a communicating branch to the axillary plexus, before its normal distribution, as in the other intercostals, to the muscles so called, which are perforated toward the sternum by the branches going to the ventral integument. The nerves answering to lumbar and sacral of Quadrupeds divide into dorsal and ventral fasciculi. The former go to the inter- transversales, spinales, interspinales, sacrolumbalis, and longis- simus dorsi; and to the superincumbent fascia and tegument. There are intercommunicating filaments between the dorsal divi- 170 ANATOMY OF VERTEBRATES. sions of the second, third, and fourth lumbar nerves. Some of the ventral branches pierce the intertransversalis before penetrating the fascia of the psoas, on their way to the oblique and straight abdominal muscles ; but the main proportion is taken by the psoas. Anterior branches from the seventh, eighth, and ninth lumbar nerves diverge from the ordinary course or distribution, and partially unite with a plexus extending to and supplying the muscles which connect the ischial or pelvic bones with the abdo- minal and caudal muscles and those of the attached parts of the sexual organs. The above nerves evidently represent the lumbar plexus developed in Quadrupeds for the hind-limbs, but their chief distribution is as ( pudenda! ' nerves. The anterior or ventral divisions of the caudal nerves mainly combine to form a nerve-trunk on that aspect of the tail, which is resolved into many small parallel transverse branches, from which are supplied the muscles and teguments of that part of the tail. The dorsal divisions are similarly distributed, but only a very small propor- tion goes to the skin. 1 In the Ungulate series the distribution of the spinal nerves has been followed by the hippotomists in the Horse and Cow; by Swan in the Ass ; 2 and I have made observations on that part of the anatomy of the Rhinoceros and Giraffe. Several branches from the superior cervical ganglion of the sympathetic join, in a plexiform manner, the anterior division of the first cervical ; this also receives a filament from the descendens noni, which previously communicates either with the trunk or a filament from the par vagum ; afterwards it joins the pharyngeal plexus, and is distributed to the steruo-hyoid and sterno-thyroid muscles. The nerve given to the serratus magnus proceeds from the sixth cervical with the phrenic ; but the phrenic after- Avards communicates with a branch of the seventh, given to the pectoralis major. The axillary plexus in the Ass, also in the Pig, is formed from the seventh cervical and the first and second dorsal nerves. The superior scapular nerve proceeds chiefly from the seventh cervical ; but in some degree from the first dorsal, and is sent to the supra- and infra-spinati muscles of the scapula. Branches proceeding from all the nerves forming the plexus are given to 1 SWAN well notes the difference between the mode of supply to the natatory tail, i.e. by a few trunks in Cetacea derived from a remotely situated myelon, and that in Fishes, by many nerve-pairs from a contiguous myelon: also the great proportion of motory as compared with sensory filaments ; the tail being not only the main motive instrument in Whales, but capable of ' giving hard blows without feeling much pain.' LIV. p. 165. 2 LIV, 2d ed. pp. 153, et. seq. NERVES OF MAMMALIA. 171 the great pectoral muscle ; a nerve proceeding principally from the last cervical and first dorsal supplies the subscapularis. teres major, and latissimus dorsi, then takes a circumflex course to the deltoid, and external head of the triceps, and finally passes down the limb to the skin. The external branches of the third and fourth dorsal nerves, also, supply the skin ; the internal cutaneous nerve is sent off from the ulnar. The musculo-cutaneous is formed chiefly by the last cervical, and partly by the first dorsal ; it contributes to the formation of the median nerve, then pierces the coraco-brachialis to terminate on the biceps. The median is mainly formed by the first two dorsal nerves ; it sends a branch to the biceps, brachialis internus, and supplies the skin on the posterior and inner part of the fore-leg. After supplying the flexors on the fore-leg, it sends a nerve close to the bone which gives filaments to the periosteum, and passes to a muscle answering to the flexor longus pollicis : it then passes underneath the annular ligament, and sends a large branch obliquely over the flexor tendons to communicate with the ulnar nerve, and descends, giving off branches to the skin at the inner side of the foot, which communicate with the inner portion of the deep palmar branch of the ulnar : it then passes to vascular lamella? attached to the hoof, fig. 17, 17, to terminate on these, on the villous part of the sole and the ligaments of the joints. The ulnar nerve arises from the first and second dorsals ; at the middle of the arm it sends off the internal cutaneous nerve, and at the elbow gives some branches to the short extensor and the elbow joint; it passes down, covered by some fibres of the flexor muscles, and at the wrist sends off the dorsal branch to the skin at the posterior and outer part of the fore-leg ; it passes under- neath and to the inner side of the flexor carpi ulnaris, and then underneath the annular ligament, and gives off the deep palmar nerve : it receives the branch from the median, and descends, o-ivino; branches to the skin and ligaments at the outer side of the O O o foot, after these have communicated with the outer branch of the deep palmar ; it passes into the foot, covered by the vascular lamellae connected with the hoof, and terminates on these, the villous part of the sole and the ligaments of the joint. The deep palmar gives some filaments to the ligaments, and divides into two principal branches, one to pass on the inner side to give filaments to the joints, the periosteum, and ligaments, and com- municate with the branches of the median sent to the skin and ligaments at the inner side of the foot, the other to s;ive filaments O 3 O to the periosteum and ligaments, and communicate with branches 172 ANATOMY OF VERTEBRATES. of the ulnar, having a similar destination on the outer side of the foot. The musculo-spiral nerve arises from the seventh cervical and first and second dorsal nerves : after supplying the heads of the triceps, it passes round the humerus, and gives branches to the two large extensors at the back of the fore-leg, and sends a branch, somewhat expanded, down to the carpal joints, but not swelling into a ganglion, as in Man ; it then pierces the rudiment of the short supinator, to supply a muscle answering to the long supinator on the outer side of the back of the fore-arm. In the Pig, the median in the fore-arm is much larger than the uluar; it receives a small communicating branch from the ulnar near the wrist, and then supplies the inner small toe (zV), both sides of the inner large toe (iii), and the inner side of the next (iv). The ulnar gives off the dorsal branch, and then sends the deep palmar to the interosseous muscles ; it contributes a small branch to the median, and then supplies the outer side of the large toe (iv), and the adjoining small toe (v). The greatest portion of the dor sum of the foot is furnished by the radial branch of the spiral nerve, and the rest by the dorsal branch of the ulnar. In the Ass there are eighteen pairs of dorsal nerves, the anterior or ventral divisions of which pass between the ribs, are distributed to the intercostal and abdominal muscles, the hind- most perforating the psoas muscle. There are five lumbar and six sacral nerves, besides four or five caudal. The third lumbar sends off a branch, which gives a branch to the great psoas muscle, and one to join the fourth for the anterior crural nerve ; it then becomes the external cutaneous nerve to pass on the outer side of the thiffh ; it sends off another laro;e branch O '' O corresponding with the external spermatic, which communicates with a large branch of the third lumbar ganglion of the sympa- thetic, gives a branch to the small psoas muscle, and then passes underneath the lower border of the abdominal muscles, to which it sends a branch, and becomes distributed on the mamma. The anterior crural nerve arises from the third, fourth, and fifth lumbar nerves : the obturator arises from the fourth and fifth lumbar, and first sacral nerves : the sciatic arises from the three first sacrals : the principal part of the third and fourth sacrals, joined by a small branch from the portion of the sciatic arising from the second, give off the internal pudenda! to pass at the side of the arch of the pubes, distribute filaments to the neck of the bladder, and terminate on the clitoris, vagina, and external parts, and the connecting muscle and membrane between these and the mamma. A branch of the external sper- NERVES OF MAMMALIA. 173 matic may be traced downward, and a branch of the internal pudendal upward, towards each other. Another part of the junction of the fourth and fifth, with sometimes a branch from the sixth sacral, joins the hypogastric plexus, and sends branches along the inferior uterine artery to the neck of the uterus and vagina, and is then distributed to the bladder, urethra, vagina, and rectum. The remaining part of the fifth and sixth sacrals forms the beginning of the anterior caudal nerve, to which the anterior trunks of the remaining spinal nerves below it become united ; the posterior trunks of these nerves form the posterior caudal nerve ; both of these are continued to the extremity of the tail, communicating by branches, and supplying one-half of each anterior or posterior surface. 1 The gluteal nerves are sent from the two first sacrals at their junction with the sciatic, and terminate on the glutei and tensor fascia?. A nerve given off from the sciatic supplies the gracilis and gemelli, and is continued down to the quadratus femoris. The anterior crural nerve sup- plies the sartorius, rectus femoris, vasti, and cruraeus. The sa- phenus nerve descends with the vein, giving numerous filaments to the ligaments and skin, and communicating at the side of the foot with the inner branch of the deep plantar nerve, and through this with a branch of the inner plantar, to be distributed on the skin at the side of the foot. The obturator nerve supplies the adductors and the large muscle corresponding with the gracilis. The sciatic nerve gives branches to the semimembrancsus, semitendinosus, and biceps ; it then divides into the posterior tibial and the peroneal, both of which give branches to the biceps. The posterior tibial sends a branch down at the back of the gastrocnemius, and on the outer side of the tendo Achillis to the fascia, on that side of the hock : it then passes between the heads of the gastrocnemius muscle, to which and the large muscle representing the posterior tibial and the flexors of the toes it gives branches ; it descends on the inner side of the tendo Achillis, giving branches to the fascia, &c. on the inner side of the hock, near which it divides into the inner and outer plantar nerves ; the inner sends off a large branch obliquely over the flexor tendon to join the external plantar nerve ; it passes down on the inner side of the tendon, giving branches to the sheath, fascia, and integuments ; near the foot it gives off a large branch, which communicates with the inner branch of the deep plantar nerve, to be distributed on the skin at the inner side of the foot ; it gives branches to the skin of the heel, and then passes down to the hoof, covered by the vascular lamella?, and distributing 1 LIV, p. 160. 174 ANATOMY OF VERTEBRATES. branches to these and the villous stratum of the sole. The external plantar passes between the flexor tendons, and then on the outer side of these, and gives off the deep plantar nerve ; it is continued down on the outer side of the tendon, gives filaments to the sheath and fascia, receives the branch from the inner plantar, and gives off a branch which communicates with the outer branch of the anterior tibial nerve, and is distributed on the side of the foot ; its ultimate distribution resembles that of the posterior tibial. The deep plantar gives filaments to the ligaments, then divides into two branches ; the inner passes down beneath the tendon, then near the edge of the bone to the foot to communicate with a branch of the saphenus nerve, and of the inner plantar, to be dis- tributed on the skin at the inner side of the foot; the outer branch passes near the edge of the bone, gives a branch to the ligaments, and then joins the outer branch of the anterior tibial nerve. The peroneal nerve passes to the outer side of the leg, and gives small branches to the fascia and skin ; it sends the long branch dow r nward which gives filaments to the fascia, and termi- nates in the skin covering the dorsum of the cannon-bone. It gives filaments to the ligaments and fascia on the outer side of the knee-joint, and branches to the peroneal muscle, the extensors of the toes, and the anterior tibial muscle. It gives off the anterior tibial nerve, which passes down the leg between the peroneal and anterior tibial muscles, then between this and the bone along with the anterior tibial artery underneath the annular ligament, where it divides into two branches ; the outer one gives filaments to the joint, and is contained with the anterior tibial artery on the outer side of the cannon-bone, giving filaments to the periosteum, and on the outer side of the foot receiving the outer branch of the deep plantar nerve ; it then becomes connected with a branch of the outer plantar nerve, and is distributed 011 the ligaments and skin on the outer side of the foot ; the inner branch of the anterior tibial passes down on the cannon-bone, gives filaments to the periosteum and fascia, and terminates on the skin at the inner side of the foot. In the Pig, the posterior tibial nerve, having given branches to the muscles of the leg, and sent the branch down at the back of the gastrocnemius muscle to the outer side of the leg, gives filaments to the inner side of the heel, and near the part divides into the inner and outer plantar nerves ; the inner is continued onwards, and supplies the small inner toe (zV), the first large toe (Hi), and the inner side of the next (iv). . The outer plantar nerve passes underneath the flexor tendon, and is continued on- NERVES OF MAMMALIA. 175 ward to divide for the outer side of the second large toe, and the outer small toe ; it sends the deep plantar into the sole to supply the short muscles situated there. The anterior tibial nerve gives branches to the ligaments at the back of the foot, and sends a branch to supply the toe, ii, and the inner side of in ; the rest of it Drives branches to the small muscles on the back of the foot. o and then passes forward to join the branch of the peroneal given to the outer side of Hi, and the inner side of iu l ; the continua- tion of the peroneal after emerging just above the instep supplie the outer side of Hi toe, both sides of iv and v, the branch sent to the outer side of Hi and the inner side of iv receiving a branch of the anterior tibial. In the order Car?iivora, the distribution of the nerves has been described and figured by Swan, in the Fox (LIV, p. 150, pi. 33), and in the Jaguar (ib. p. 161), from which the following account is chiefly abridged. In the Fox the anterior trunk of the first cervi- cal passes forward, and sends up two filaments to the junction of the trunk of the par vagum with the glosso-pharyngeal, the ninth, the* accessory, and the superior cervical ganglion of the sympathe- tic ; it gives branches to the recti antici, and then joins the descen- dens noni, to be distributed to the sterno-hyoid and sterno-thyroid muscles. The posterior trunk supplies the recti capitis postici and obliqui sup. et inf. The anterior trunks of the second and third cervical nerves give branches to the recti capitis antici, then unite to communicate with the accessory, and divide into branches, which are distributed on the cutaneous muscle and skin at the side of the face and neck and external ear. The fourth cervical gives a branch to join the accessory and others to the trapezius, and is then distributed to the cutaneous muscle and skin at the side of the neck. The fifth cervical nerve gives a branch to the acces- sory, and to the trapezius, and then pierces this to terminate on the skin at the lowest part of the neck. The posterior or dorsal division of the second cervical nerve gives branches to the splenius, complexus, and other muscles, close to the posterior part of the spine, and then sends a branch through the complexus towards the occiput, which gives filaments to the muscles inserted into the back of the ear, but is chiefly distributed on the skin of this part, The posterior division of the third cervical is similarly distributed. That of the fourth cervical gives branches to the complexus and other muscles close to the spine, and then terminates on the skin. The posterior divisions of the sixth and seventh also give branches 1 See vol. ii. p. 308, fig. 193, Hippopotamus, which resembles the foot of the Hog. 176 ANATOMY OF VERTEBRATES. to the muscles and skin ; the first dorsal supplies the muscles only. The phrenic nerve is formed by a branch from the fifth and sixth cervicals : it passes over the pericardium to the dia- phragm, and on the right side is placed close to the post-caval vein. In the Jaguar, the phrenic also arises from the fifth and sixth cervicals, and receives a branch from the first thoracic ganglion. The axillary plexus is formed by the last two cervical and first two dorsal nerves. In the Fox the axillary plexus is formed by the sixth and seventh cervical and first and second dorsal nerves, but the greatest part of the sixth, after receiving a branch from the seventh, gives a large branch to the integuments on the anterior part of the shoulder-joint, and then passes to form the superior scapular nerve, and terminates on the supra- and infra-spinate muscles. Branches from the sixth and seventh cervical and first and second dorsals are given to the pectoral muscles ; a branch from the seventh cervical is given to the serratus magnus, and branches from the sixth and seventh go to the subscapularis. The circumflex nerve arises from the union of the sixth and seventh cervical nerves ; it gives branches to the subscapularis and teres major muscles, and then divides and sends a branch to the infra-spinatus muscle and the deltoid, and branches to the integuments on the. outer side of the arm. The internal cutaneous nerve is sent off by the ulnar ; it passes down the arm, and, near the inner condyle of the humerus, divides into branches to be distributed to the skin at the ulnar side of the fore-arm. The smaller internal cutaneous nerve is the external branch of the third dorsal after its egress from between the ribs ; it pierces the broadest muscle of the back, and divides into branches, to be distributed on the skin at the inner and posterior part of the arm. The musculo-cutaneous nerve arises from the seventh cervical with the outer portion of the median, gives a branch to the pectoralis and coraco-brachialis, and then passes off to terminate on the biceps. The seventh cervical, having given off the homologue of the musculo-cutaneous, the remaining part gives off a branch which sends one back to the brachialis internus, behind the tendon of the biceps, and then gives branches to the skin of the fore-arm, in the place of the cutaneous portion of the musculo-cutaneous nerve in Man ; it then joins the branch from the first and second dorsal nerves, about an inch above. the elbow, to form the median nerve, which is small as compared with that in Man. The nerve thus formed passes under the origin of the pronator teres, and gives branches to this, the flexor carpi radialis, and the superficial and deep flexors of the digits ; it then passes, SERVES OF MAMMALIA. 177 by the side of the radial flexor and between the digital flexors. / ^j through the annular ligament ; it is continued in the fore-paw between the tendons of these muscles, at the division of which it sends off branches ; it gives filaments to the skin of the palm, and a branch to the rudimental pollex, 1 another to the inner side of the index (n), and a branch to be joined by one from the deep palmar for the outer side of the index and the inner side of the medius (in) ; another branch also to be joined by a branch from the deep palmar for the outer side of the medius and the inner side of the annularis (iv). The ulnar nerve is formed by the first and second dorsals ; it descends behind the inner condyle of the humerus, covered by thick fascia and by part of the flexor sublimis ; it then passes down the fore-arm between the flexors of the fingers and the ulnar flexor of the wrist. In the fore-arm it is larger than the continuation of the median nerve : it sends a branch to the ulnar side of the superficial and deep flexors of the digits and the ulnar flexor of the wrist : near the hand it sends a branch to the back of this part to communicate with the radial branch of the musculo-spiral nerve, and then proceeds to the outer side of the fifth digit (v) ; it passes deeply, confined by a ligament at its entrance, into the palm, and sends a branch for the inner side of the fifth digit and the outer side of the fourth ; the rest of the nerve, forming the deep palmar, divides into branches, which terminate on the interosseous and other small muscles situated in the palm, and give branches to join those of the median sent to the outer side of the index and the inner side of the medius digit ; also to the oiiter side of this and the inner C5 side of the annularis. The distribution of the median nerve is nearly the same in the Felines, but the trunk traverses the ento- condyloid canal. The musculo-spiral nerve has a slight com- munication with the sixth cervical, but is principally formed from the seventh and first and second dorsals ; it gives branches to the different heads of the triceps muscle, and winds round between the inner and large heads of the triceps to the outside of the arm, and divides into two large branches ; one gives off a cutaneous branch to the outer side of the fore-arm, and then descends in the place of the radial, giving branches to the skin, and dividing to terminate on the skin at the back of the paw and the side of each digit, except the outer side of the fifth, and communicate with the dorsal branch of the ulnar ; the other, in passing to the back of the fore-arm, gives a branch to the long and the short supinator muscles ; it then divides to terminate in the extensor carpi radialis 1 Vol. ii. p. 306, fig. 191, Hycena, i, which also serves to exemplify the homology of the digits of the fore-paw in the Dog and Cat. VOL. III. N 178 ANATOMY OF VERTEBRATES, and the extensor digitorum, whilst a long branch passes on and gives filaments to the extensors of the pollex and to the wrist- joint, but does not terminate on this part in a ganglion, as in Man and Quadrumana. There are thirteen pairs of dorsal nerves, and their principal deviation from those in Man consists in a smaller size, a more direct course, and a less distribution on the abdominal muscles, and by those at the lower part of the thorax being covered by an extension of the origin of the psoas muscle, also in the anterior cutaneous branches supplying the different portions of the elongated mammary glands in the female, as well as the skin. The posterior or dorsal divisions, after supplying the muscles connected with the spine, the sacro-lumbalis and longissi- mus dorsi, send a branch between these and the latissimus clorsi to the skin. The anterior or ventral divisions of the lumbar and sacral nerves supply principally the parts connected with the lower extremity, the bladder and rectum ; the dorsal divisions of the second and third lumbar nerves supply the skin as well as the sacro-lumbalis and other muscles connected with the dorsal parts of the vertebras ; the dorsal divisions of the succeeding lumbar nerves are distributed to the muscles only ; the dorsal divisions of the sacral nerves supply the muscles on that surface of the tail. The nerves are not very different from those in Man, except in their number, and consequently in their conjunction a little higher or lower for forming the nerves of the lower extremity. The anterior divisions of the three first lumbar nerves give fila- ments to the psoas muscle, and then pass forward to terminate in the abdominal muscles and skin. The fourth gives filaments to the psoas and internal iliac muscles, and sends a branch to join one from the third to form the external spermatic on the external iliac artery, which passes through the external abdominal ring to the spermatic chord ; in the female this was distributed on the posterior division of the mammary gland ; it sends off another branch which gives a filament to the external iliac artery, and then joins the sixth ; the rest of the fifth passes down on the exterior of the thigh to the skin, and forms the external cutaneous o nerve. The sixth receives a branch from the fifth, gives fila- ments to the internal iliac muscle ; part of it is then joined by a large branch from the seventh to form the anterior crural nerve ; the other part, after receiving a large and small branch from the seventh, becomes the obturator nerve. The seventh, having given off the preceding branches, joins the first and second sacrals and a branch of the third for forming the sciatic nerve. The NERVES OF MAMMALIA. 179 junction of the first and second sacral gives a branch to the pyri- forin muscle, and a larger one to pass out at the ischiatic notch to supply the gluteal muscles and the tensor fascia?. Some branches derived from the second and third sacral nerves combine with the hypogastric plexus for supplying the bladder and rectum, and others from the pudenda! nerves for the muscles connected with the anus and tail. A branch of the second sacral nerve joins the third for forming the anterior caudal nerve, which receives the anterior trunk of each remaining spinal nerve, and passes deep in the anterior part of each side of the tail, giving off branches into its course ; the posterior or dorsal trunks of the same nerves form a nerve, which also sends off branches to the dorsal muscles and skin of the tail. The anterior crural nerve passes between fibres of the iliac muscle, then under Poupart's ligament at the inner side of the sartorius ; it gives branches to this, to the rectus femoris, the external and internal vasti, and the cruralis, and sends off the saphenus nerve, which descends across the thigh to the inner part of the leg, communicates with a filament from the obturator, and O 7 is continued to the foot, giving filaments in its course to the fascia and skin. The obturator nerve, on emerging from the y O O pelvis, gives branches to the pectineal muscle, the triceps, and gracilis, and sends a branch to communicate with the saphenus nerve ; several fine branches pass down on the inner side of the thigh for the fascia and integuments. The sciatic nerve, O O * on emerging from the pelvis, communicates with the internal pudendal ; it sends a branch to the internal obturator muscle, and one which gives a filament to the upper portion of the gemelli, and then passes behind the tendon of the internal obturator to the lower portion of the gemelli and quadratus muscles. The sciatic passes close to the insertion of the in- ternal obturator muscle, and upon or behind the gemelli and quadrati muscles, then behind the trochauter covered by the origin of the biceps to which it gives a branch : it sends off a large branch w r hich divides into others for the semimembranosus and semitendinosus muscles. About the middle of the thigh it sepa- rates into the posterior tibial and peroneal nerves. The posterior tibial nerve sends off a long slender branch which descends on the posterior part of the gastrocnemius muscle to the outer side of the leg, sends a branch behind the tendo A chillis to the posterior tibial nerve, and is distributed on the skin at the outer side of the leg and heel. It then gives N 2 ISO ANATOMY OF VERTEBRATES. branches to the gastrocnemius, and passes between the heads of this and gives branches to the flexor of the toes, the tibialis posticus and the flexor longus hallucis ; it then passes down the leo; on the inner side of the tendo Achillis, and receives the O ' branch from tlie long slender branch, sent underneath this tendon. It passes behind the inner condyle of the tibia, and divides into the inner and outer plantar nerves : the inner plantar gives a branch to the inner side of the second toe, and then communicates with a branch of the deep plantar, and divides for the outer side of the second and the inner side of the third ; it also communicates with a branch of the deep plantar given to the outer side of the third toe and the inner of the fourth ; the outer plantar nerve passes between the flexor tendons, and sends a nerve to the outer side of the foot and the last toe ; it gives off the deep plantar, which passes underneath the short flexor of the toes, and divides into branches, and gives filaments to each of the small muscles situated in the sole of the foot, and a branch to communicate with one from the inner plantar nerve : it then divides for the outer side of the second toe (the innermost in the Fox and most digitigrades) and the inner side of the third, and one for the outer side of the third and the inner of the fourth, and another for the outer side of the fourth and the inner of the fifth toe. The peroneal nerve gives a small branch to the biceps and filaments to the fascia near the knee ; it then divides the anterior tibial nerve, sends off branches to the anterior tibial muscle, the long extensor of the toes, and the long peroneal, and descends with the anterior tibial artery, beneath the annular ligament, and gives branches to the ligaments of the foot ; it passes on- wards, and is joined by a branch from the continuation or dorsal branch of the peroneal, and divides for the outer side of the second and the inner side of the third toe. The continuation or dorsal branch of the peroneal, gives branches to the short and third peroneal muscles, and passes behind the long peroneal, and emerges between this and the long extensor of the toes ; it passes over the annular ligament, and sends a branch to the outer side of the foot and the fifth toe ; on the back of the foot it sends the branch to join the anterior tibial nerve ; it separates into two branches, the first divides for the outer side of the third and the inner side of the- fourth toes, the other for the outer side of the fourth and the inner side of the fifth or outermost toe. The chief characters of the minutely detailed distribution of the myelonal nerves of Man, in works on his anatomy, are found in most Quadrumana. Mr. Swan has remarked that the saphenus NERVES OF MAMMALIA. 181 nerve is proportionally larger in a Baboon : and he also notices the large size of this nerve in the Jaguar. The nerves of the palm are proportionally smaller in Apes than in Man, and do not terminate in such thick brushes of filaments at the tips of the fingers ; but the branches from the musculo-spiral and ulnar nerves to the back of the hand are larger in proportion than in Man. 1 Many Quadrumaiia have the ganglion on the termination of the spiral nerve at the back of the wrist ; but in the Felidce there is only a slight enlargement at that part of the nerve. 212. Sympathetic system. This, as an addition to the general nervous system, is a speciality of the Vertebrate subkingdom : as such it dawns in Myxinoids, at the confluence and intestinal production of the two vagal trunks, and is differentiated by pro- gressive steps, till it attains the general condition defined in vol. i. p. 318, 57. 2 TVhere it begins in the series there the chief centres are after- wards established, as the semilunar ganglions and solar plexus, so called from the multitudinous rays that diverge therefrom ; they are early and distinctly visible in the mammalian embryo. The ganglions of the sympathetic vary in the proportion of the grey or cellular and filamentary or tubular constituents. The cellular part forms a greater proportion of the semilunar ganglions in Man than in most lower Mammals : and it is greater in Car- nivora than in hoofed quadrupeds. The filaments radiating from the semilunar o-ano-Kons collect themselves into interlaced o o groups named after the viscera they mainly supply, as, the 4 gastric,' ( hepatic,' ' splenic,' ( mesenteric,' ' renal,' t spermatic,' &c. : the chief branches of all these plexuses attach themselves to the arteries of the several organs : in the large gastric plexus of the Ruminants they accompany these to the several divisions of the complex stomach. In the Carnivora branches of the superior mesenteric pass in a more definite form to the aggregate of mesenteric glands at the root of the mesentery. In Perisso- dactyles, in which the cascum and colon are remarkable for size and complexity, the superior mesenteric plexus, supplying these parts of the large as well as the small intestines, is proportionally larger than in other Mammals, especially as compared with the inferior mesenteric plexus in Carnivora and Quadrumana. In 1 LIV. p. 193. Much of the foregoing description is abridged from this rich store- house of Comparative Neurology. 2 This true idea of the series of ganglions and nerves, called 'sympathetic' in Man, once clearly attained, will leave little room for speculations as to whether the ner- vous system of insects answers to the myeleneephalic or sympathetic part, exclusively, of that of Vertebrates, 1S2 ANATOMY OF VERTEBRATES. 137 Re the Baboon the caecum and about one foot of the colon is supplied by the superior mesenteric plexus, and the remaining five feet of the large intestine by the inferior one. In Carnivora this sup- plies about the terminal half of the large intestine. In the baboon Swan noticed a communication between the right phrenic nerve and the semilunar ganglion. 1 The trunk, advancing or ascending from each semilunar gan- glion, is an aggregate of cords (' splanchnic nerve,' Anthropotomy), which, perforating the diaphragm, separate to form communica- tions with a variable number of the thoracic ganglions of the sympathetic. In the baboon Swan traced the origins or con- nections of the right splanchnic nerve with two thoracic ganglia in advance of the left, this extending over the heads of five posterior ribs, and the other over seven, each ex- panding into a small ganglion at the bottom of the chest. In the hedge- hog the splanchnic nerve extends over the heads of the four last ribs, and, receiving filaments from the sympa- thetic, forms a plexus on the sides of the vertebra?, as in the baboon ; but separates from the trunk of the sym- pathetic higher in the chest. In the jaguar this separation occurs a little above the diaphragm : in the hog at the passage through the diaphragm. But ' these variations do not seem to make any difference either in the for- mation of the semilunar ganglion, or the branches preceding from them.' 2 Kolliker has given the subjoined view, fig. 137, of the communication of the splanchnic, Spl, with the myelon by the ' rami communicantes ' Re, ftc, and with the ganglion of the sympathetic, G, from which it derives its grey fibres. From the trunk of the sympathetic TV and the ganglion the nerve s to the intercostal artery is sent off. In Mammals the parts regarded as ( trunks,' or i main chords' 3 of the sympathetic, form a symmetrical pair extending along the sides of the centrums, forward to the basioccipital, and backward 1 LIV. p. 115. 2 Ib. 3 ' Prolongations,' SWAN. LIV. passim. T Sixth thoracic ganglion of sympathetic, RaVibit. Lxxvui". NERVES OF MAMMALIA. 183 Section of sixth intercostal with communicating branch to sympathetic. Rabbit (mag. 60 diam.). LXXVII-. A 139 to the coccyx : anteriorly, or above, they pass to ganglions and plexuses, within, or about, the cranial -,& 7 cavity ; below or behind, they con- verge and unite, generally, in a ter- minal f coccygeal ganglion. In their course the cords cross, ventrally, the issuing trunks of the spinal nerves, with which they are connected by short threads, including grey and white fila- ments, and there usually swelling into ganglions. The grey or gelatinous thread is most probably a contribution from the ganglion to the myelonal nerve, the white thread is sent from the nerve to the sympa- thetic ganglion : it consists of tubular nerve-fibres, and these predominate in the ' rami communicantes ' of the rabbit and cat. 2 Under a power of sixty diam. after addition of dilute solution of soda Drum- mond found such fibres con- tinued mainly from the mye- lonal end or origin, fig. 138, C, of an intercostal nerve, and converging to form the com- municating branch, RC, with the sympathetic ganglion. A few filaments, , , disappear among those of the intercostal nerve rather in the direction of its outward course. Traced tO the Sympathetic gailgllOn, Fourth thoracic ganglion, with course of fibres received ,1 I by the communicating branch, c, from the myelou. iiiey diverge, (Mag 70 diain.) 1 Lxxvii". p. 446. B in fio- ng. 184 ANATOMY OF VERTEBRATES. spreading over its cellular part , and in greater propor- tion at the surfaces a a, cc. Thus, at certain portions of the tongue, three sets Section of cortical layer, upper part of tongue. O f fibl'CS traVCl'SC til 6 SaillC (30 diain.) CCXL. area, in as many distinct directions and at right angles one with the other ; the arrange- ment being so that the crossing of the fibres of any two sets forms 1 a faces emerge ORGAN OF TASTE IN MAMMALIA, 201 a net, the meshes of which in successive layers become canals through which the fibres of the third set pass ; hence in whatever plane they be viewed, two sets are seen, in profile, crossing, and one, in section, perforating ; by which arrangement they mutually support and conduct each other, independently of connective tissue, the dispensing with which allows for the aggregation of so much more muscular tissue in the tongue's substance. In fig. 147, a magnified view is given of a section from the upper surface, a, in fio-. 145 : a are the vertical fibres extending to that surface, be- O O J yond the uppermost transverse fibres, b, and decussating with the longitudinal fibres shown in section at c. This complex arrange- ment becomes simplified toward the apex : the longitudinal fibres first ceasing, next the vertical ones, and the transverse alone being continued to the tip. 1 The skin of the tongue is divided into the papillose, glandular, and smooth, mucous, or faucial areas : the latter, fig. 141, d, has about half an inch of longitudinal extent when not stretched, and answers to the much more considerable tract in the Lion. The glandular area is defined anteriorly by the fossulate papilla, ib. /, here arranged ( en chevron,' four on each side converging toward the backwardly turned point : behind this is sometimes seen a fossa devoid of papilla, the ( foramen caecum ' of Anthropo- tomy. The papillose area extends over the major part of the tongue to its tip and down the sides along part of the under surface ; it is roughened by papillae which extend from the medial groove in oblique series forward and outward, repeating in the main the arrangement of the fossulate or glandular o o papillae. The tongue-skin presents a basal areolar tissue, so dense in the glandular and papillose area? as to resemble the corium : at the faucial area and under surface of the tongue it softens into the character of that of the mucous membrane of the cavity with which it is continuous : where it overlies the muscular part of the tongue, as in fig. 145, a, it is closely adherent thereto, and is thickest at the middle line : peripherally it projects as ' papillae,' sinks into ' fossulaa,' and is inverted to form the ducts or orifices of mucous follicles. The epithelium is scaly, thick and distinguishable into a deep layer adherent to the corium and a superficial layer which readily desquamates. The so-called 1 papillae ' are processes of the corium, rather analogous to the 1 For further and more minute details of this exquisite arrangement of the mus- cular tissue for the functions of the tongue, reference should be made to the admirable article CCXL, in which the accomplished author, HYDE SALTER, first described it. 202 ANATOMY OF VERTEBRATES. 148 villiform ones in the intestinal mucous membrane of some animals (vol. ii. p. 170), and subdividing, as in those, into the ' villi ' or papillae truly answerable to those of the skin ; the tonguc- papilla) or processes differ, therefore, from the true dermal papilla? in standing freely out from the surface of the epithelium, which is moulded upon them, and does not plaster them over to its own level. The so-called lingual papilla are of three kinds, f fossulate' or circumvallate, ' fungiform,' and f conical,' many of the latter bcins; also called ( filiform.' o The fossulate papilla, fig. 148, a, is large, obtuse, subpedun- culate, and arises from a fossa, b, by the thickened and often crenate borders of which, c, it is surrounded. The nerves and vessels enter the papilla at its pedicle ; and the expanded sum- mit subdivides into the secon- dary true papilla), plastered over by the epithelium. The average number of fossulate papillae in Man is eight, arranged as in fig. 14 1,/: there be sometimes ten, rarely more ; often fewer than eight, but not less than four. Their arrangement may vary to that of an almost transverse line. They are supplied by branches of the glossopharyngeal ; are very vascular ; and, from the thinness of the epithelium, appear red when injected. The 'fungiform papillae/ fig. 149, B, are subpedunculate, but 149 Section of fossulate papilla (10 diam). CCXL. Fungiform papillae, cxi". smaller than the fossulate and rounder : they are scattered over the sides and tip of the tongue, and on the dorsum anterior to the fossulate series. They are rather larger than the filiform, and conspicuous by their red colour. They are covered by ORGAN OF TASTE IN MAMMALIA. 20.-J 150 151 secondary papilla?, ib. A, in which the capillaries diverge and divide to form their brush of loops, as in fig. 149, B, receiving each its capillary loop, into the fasciculus of which the branch of the artery a and vein v sub- divides on entering: the O mushroom-like papilla or process. The conical papillje clothe as in a close-set pile the anterior two-thirds of the dorsum : they are longest at the mid-line near the centre of the tongue, small- est near the sides and at the tip. The cone-form, with secondary papillae down its sides,fig. 150, merges into the cylindrical form, fig. 151, with a terminal brush of filaments. The excess of the scaly covering of these, ib. a, b, c, forms the so-called ' fur ' of the tongue, which becomes separated from the deeper layer of epithe- lium, d. In the conical variety, fig. 150, a is the basal mem- brane, b, c, the ' processes,' sub- dividing into secondary or true papillae, e, the deep layer of epithelium, f, the superficial layer, //, the points from which the filamentary prolongations would have projected : these sometimes resemble fine hairs. The function of such filiform papilla? appears to be ' portative ' and ( protective,' that of the coni- cal papillae mainly ( tactile,' that of the fungiform and fossulate ones ( gustative : ' behind the latter are the principal mucous follicles. The so-called gustatory branch of the fifth supplies the fungi- form, conical, and filiform papillae ; the glossopharyngeal serves Filiform papilla. CCXL. 204 ANATOMY OF VEBTEBEATES. tlic fossulate papilla? and the mucous tract behind : the ninth or hypoglossal is expended upon the muscular tissue. 215. Organ of Smell. Most Mammals are remarkable for the degree in which the sense of smell is serviceable. The class is characterised by the extent of the pituitary surface and the size and number of the olfactory nerves; nevertheless, both ex- tremes are therein exemplified, although the family (JDelpMnidoz) in which the organ is wanting is exceptional and maximised development the rule. The progress is not, as with the organ of taste, pari passu with the rise in the class : both Man and monkeys are below most quadrupeds in olfactory endowments. In hoofed ones smell is important in the the discrimination of wholesome from noxious food : taste would be a tedious test, the sapid matter needing to be moved about or masticated, mixed with fluid, and more or less dissolved, before the tongue can exert its gustative power ; but ( smell is done at once.' 1 Most flesh-feeders scent afar their food. In Mammals, as in all air-breathers, the odorous atoms strike upon the olfactory membrane at the entry of the breathing passages, where the atmosphere is filtered, as it were, through the organ of smell before reaching the windpipe ; and most effectively and instructively in the pinnigrade Carnivora. The olfactory organ in Mammals receives its special endowment from nerves which rise in numbers from their proper encephalic centre, fig. 46, 47, R. They pass out by as many holes in the plate of the prefrontal, which is thence called the ( cribriform,' or, from the Greek-root, ' ethmoid:' but the sieve-like structure is a strictly mammalian peculiarity consequent on the multiplicity of olfactory nerves, and is only affected by a single exception in this class, the Ornithorhynchus adhering to the wider Vertebrate rule. The nerves carry out with them, each an investment of the brain-membranes ; the dura mater losing itself in the periosteum, the pia mater in neurilemma, the arachnoid being reflected back. The nerves are grouped in all Mammals into a set for the septum, and a second for the upper or ethmo-turbmals, a third or middle short set being, in some, distinguishable for the labyrinth or roof of the nasal chamber. The branches of the second set, after expanding on the ethmo-turbinal, usually converge to become connected with the lateral nasal branch of the ( fifth.' Their mode of distribution is best seen on the ethmo-turbinal : 1 xx. vol. iii. p. 86. ORGAN OF SMELL IN MAMMALIA. 205 here they divide, subside, expand, and anastomose with each other, forming a reticulate nervous expanse, with long and narrow meshes, and becoming impacted in the central or inner layer of the olfactive membrane. This membrane is continued into the pi- tuitary one, covering the inferior spongy bone or 'maxillo-turbinal' supplied mainly by the fifth. Both tracts, and especially the latter, are richly supplied with arteries opening into numerous large plexiform veins on the peripheral side of the membrane, occasioning or resembling, there, a cavernous structure, and O o- 7 admitting of such change in the quantity of blood therein as must be attended with concomitant degrees of laxity or tension of the scentino- membrane itself. 1 This at the attachment of the tur- o binals is continuous with the lining of the nasal chamber ; which itself becomes modified into the more delicate and still less vas- cular membrane of the contiguous or accessory air-sinuses. The nasal membranes are finally continued at the posterior aperture into the mucous membrane of the fauces and pharynx, and at the anterior one into the integuments of the face. The pigmental layer of the skin is soon lost within the nose, the colour of the pituitary and olfactory membranes being due -to the abundant blood sent to them. Numerous mucous crypts are imbedded in the pituitary part of the nasal membrane. The cavity containing the organ of smell is formed by the prefrontal, vomerine, nasal, sphenoid, pterygoid, palatine, max- illary, and premaxillary bones, and may be continued by exten- sion of air-sinuses into all the bones of the cranium, figs. 1 54 and 157. The cavity is divided by a medial partition of bone and gristle in varying proportions, the bone being contributed by the prefrontals, the vomer, and by ridges of the nasals, palatines, maxillaries, and premaxillaries, with which the vomer may articulate. Each half of the cavity is a passage for the respiratory currents of air, opening anteriorly upon a more or less produced and mobile part called ' nose,' ' snout,' or f proboscis,' and pos- teriorly into a cavity containing the larynx or beginning of the windpipe; sometimes, as in Cetacea and in Marsupials at their mammary stage, containing the larynx exclusively, but commonly communicating also with more or less of the pharynx. In the section of the human skull, fig. 152, the outer wall of the right nasal passage is shown, with the communicating frontal, 3, and sphenoidal, 4, sinuses ; i is the nasal bone, and a the nasal spine 1 Lxxxii--. p 278, and LIV. p. 123. (The second edition of this valuable aud original work, 4to, 1864, is the one cited in the present volume.) 206 ANATOMY OF VERTEBRATES. 152 of the frontal, forming the fore part of the roof, c, the basi- sphenoid, forming its back part ; the ' cribriform plate and spine ' of the prefrontal completing the roof: I is the nasal plate of the maxillary bounding laterally the anterior aperture; d, pterygoid, similarly bounding the posterior aperture : the floor of the passag< is formed by the premaxillary, 7, the maxillary, k, and the pala- tine, G. At the upper part of the outer wall is a thin quadrilateral part of the prefrontal sculp- tured by grooves and aper- tures for the olfactory nerves; the posterior part, f, is a little curved, and leaves a space into which the sphenoi- dal sinus opens. The con- volute, thin, reticulate, bony, and gristly lamina, called 6 superior turbmal,' is here attached, below which is the division of the general pas- sage, called e superior mea- tus.' This is bounded below by a similar longer and larger ( turbmal, ' called ' middle spongy bone' in Anthropo- tomy, but usually less dis- tinct from the upper part of the * ethmo-turbinal ' in lower Mammals. The part of the passage between the middle and lower turbinal is the ( middle meatus,' into which the ' antrum ' or maxillary sinus opens. The lower turbinal is the largest of the three, and longest retains its indi- viduality : below it is the s inferior meatus,' /, into which the lacrymal canal opens. In most lower Mammals there is a turbinal process from the frontal and nasal bones ; which, from its relative position in their horizontally elongated nasal chamber, is called the ( superior spongy bone ' (oberste muschel, Gurlt), by Hippotomists ; it is not the homologue of that so called in Anthropotomy. At the floor of the lower meatus, close to the premaxillo- m axillary ridge supporting the fore part of the septum, is a depression or groove lined by a glandular tract of the pituitary membrane which, in Ungulates, is extended upon a long and narrow gristly sheath at that part, and communicates with the palate by the foramen incisivum. From one to three of the ei)tal branches of the olfactory, traceable from a yellowish grey A icw of the outer wall of the nasal cavity ou the right side. ORGAN OF SMELL IN MAMMALIA. 207 part of the rhiiiencephalon, are continued clown to this tract ; but it is principally supplied, like the lower turbinal, by the naso- palatine nerve. 1 Characteristic of the mammalian organ of smell is the great O a provision made by bony and gristly laminae for the support of the olfactory membranes. The original extent of these primi- tive capsules is augmented, as in a branchial organ, by manifold plicae and processes, usually so curved and contorted as to suggest the resemblance to turbinate univalves. The neurapophyses transmitting the nerves of the nasal segment of the skull are reduced, as has been shown, in Mammals, almost to their essential function ; as such they appear in Celacea (vol. ii. p. 421, fig. 287, H ). So reduced and withdrawn from outward view, they are further masked in the rest of the class by the agglutination thereto, or outgrowth therefrom, of the turbinal olfactory capsules : the whole, as agglomerated in them, receiving the name of ( sieve-bone ' (ethmoid), from the exceptional pecu- liarity of the number of olfactory nerves in the Mammalian class. In fig. 153 is given an oblique view of this complex bone with the anchylosed sphenoid in the Hog. The confluent mesial 153 Osseous parts of olfactory capsules. Hog. laminae of the prefrontals project as ' crista galli ' dividing the rhinencephalic fossae : to the under or outer part of the cribriform or perforated laminre of the neurapophyses the parts of the olfactory capsules called < labyrinths,' q, and ethmoturbinals, .9, are anchylosed : the maxilloturbinals, p, remain longer distinct, and ultimately coalesce with the superior maxillaries. The con- volute plates attached to the roof of the nasal chamber, fig. 157, /;, here called ' naso-turbinals,' are in most quadrupeds added to those shown in figs. 152 and 153. 1 XC", CXJl"', 208 ANATOMY OF VERTEBRATES. In the Ornithorhynchus one olfactory nerve quits each rhincn- cephalon and escapes from the skull by a single foramen at the fore part of the prefrontal plate : it divides on entering the nasal cavity into septal and turbinal branches. The membrane re- ceiving the former is supported wholly on a bony plate : the turbinals are partly bony, and partly gristly : a prenasal ossicle is formed in the forepart of the nasal septum. The olfactory nerves in the Echidna are extremely numerous, and the cribriform plate is large and encroaches upon the fore part of the cranial cavity as a convex protuberance. The ethmo- turbinals are of corresponding size, composed of a series of vertical processes which expand and subdivide as they pass toward the floor of the very long nasal passage. I have shown the lateral expanse of these turbinals by a horizontal section in No. 1707, XLIV. p. 318. The olfactory nerves and the osseous cavities and laminre destined for the protection and support of the pituitary membrane offer a remarkable proportional development in all the Marsupials, and more especially in the Insectivorous and Carnivorous tribes. Certain species of Kangaroo, of the subgenus Osphranter, Gould, remarkable for their acuteness of smell, have the turbinated bones so large that the lateral expansion of the nasal cavity forms a marked feature in the skull. The characters of the osseous parts of the nasal cavity, in this order, are given in vol. ii. p. 348. Through the defective ossification of the palate the convolutions of the inferior turbinals are visible in the dry skull at that part ; e.g. in Perameles layotis (vol. ii. fig. 222) and in Thylacinus. In the latter marsupial the fine lacework perforation of the inferior turbinals is well shown. In the Hare the inferior turbinal is large, longitudinally la- mellate, and shows in well-injected specimens the highest degree of vascularity : the complexity of its medial or septal surface contrasts with the simplicity of that in Felines. The ethmotur- binals are divided into three principal lamellrc : the nasal cavity is long but narrow : the maxillary sinus is small. In the Agoutis the nasal chamber is more expanded : the ethmoturbinals which consist each of four rather short longitudinal lamella, are divided from the maxillo-turbinals by a protuberance from the mesial wall of the large maxillary sinus : there is a small ' Jacobsoii's' process from the premaxillary at the lower and fore part of the nasal cavity. In the Paca ( Ccdogenys) the olfactory cavity ex- tends backwards beneath the rhinencephalic one. In the Porcu- pines through the enormous development of sinuses from the olfactory cavity it extends backward beyond the rhinencephalic ORGAN OF SMELL IN MAMMALIA. 209 one, which it appears to encompass. The latter cavity is defined by a well-marked ridge from the prosencephalic part of the cranium. The vomer is deeply cleft posteriorly, and coalesces with the ethmoturbinals. The fore part of the vomer articulates with the median ascending process of the premaxillary arching over the wide vacuities which lead from the nasal passages to the prepalatine apertures. Besides the maxillary sinuses others are developed in the frontals, squamosals, alisphenoids and orbito- sphenoids, with bony septa converging to the rhinencephalic fossa?. No nasal sinuses or aircells are developed in the skull of the aquatic beavers. In the voles (Arvicola) a canal leads from the crescentic orifice at the fore part of the antorbital aperture into the lower part of the nasal meatus, above the pre- palatine fissures. In the rat (Mus decumanus) it terminates below the attachment of the anterior turbinal to the premaxillary. In all Muridce the olfactory cavity is very narrow ; the ethmo- turbinal small and but little divided ; the lower turbinal is ele- vated in position. The external nose is short and, as in most Rodents, is clothed with hair save at the middle of the septum. In Insectivora the olfactory organ is better developed than in Rodentia. The ethmoturbinal of the mole has not fewer than eight primary lamella? ; but the maxilloturbinal is comparatively simple : the external nose is developed into a snout, with well- marked muscles for various and powerful movements. The de- velopment of this part is such in some African Insectivora, fig. 297, as to have earned for them the name of ( Elephant-Shrews.' The naked outer border of the nose in the common hedgehog is den- tated : and the edge of the snout is fringed in Condylura with a circle of soft processes. But these, like the still more extra- ordinary dermal appendages in certain bats (Rhinolophus) relate to touch. The armadillos and anteaters enjoy an acute sense of smell. In Dasypus sexcinetus the rhinencephalic almost equals the epencephalic division of the cranial cavity : but the olfactory chamber extends backward to beneath the prosencephalic division, and the ethmoturbinals are remarkably extensive and complex : the maxilloturbinal is comparatively simple. The turbinal plate of the nasal almost equals the facial plate in extent. The chief expansion of the cranium is caused by the large olfactory cavity, and the part extending therefrom into the frontals raises them in Chlamyphorus into a pair of domes (vol. ii. fig. 272, a). In most Armadillos the external nose or snout is strengthened by a pair of prenasal ossicles. The rhinencephalic chambers are large in VOL. in. p 210 ANATOMY OF VERTEBRATES. 154 Orycteropus (ib. p. 404) ; but the olfactory ones are far more remarkable for both size and complexity. In the true Anteaters (Myrmecophaga) the cthmoturbinals, though large, are less de- veloped than in armadillos. The inferior turbinal is a long slightly rolled up lamina. In sloths, as described in vol. ii. p. 406, the olfactory chamber extends backward above the rhinencephalic one into the frontal bone, and below it into the sphenoid. The extension of air-sinuses therefrom is still greater in the extinct megatherioids (ib. 407). The baleen-bearing whales are those of the Cctacea which alone have olfactory nerves, although all possess the ( crura rhinencephali.' The pituitary membrane supported by the tur- binal bone is remarkable for the plexus of large vessels behind it. The cetacean modifications of the nasal passages will be described with the respiratory organs, to which they mainly relate. In Sirenia the nostrils are subterminal, at the top of the obtuse muzzle, and provided with movable gristles : the nasal passages contain both ethmo- and maxillo-turbinals, the latter, like the former, gristly ; the small almond-shaped bones wedged into the fore part of the frontals are, as Cuvier held, nasals, not turbinals. 1 The nasal passages are short, narrow, sub vertical : the ethmoturbinal is short and longitudinally lamellate. The olfactory nerves are fewer and the cribriform plates smaller in the Dugong than in the Manatee. In the Elephant that part of the nasal cavity, fig. 154, which is appropriated to the essential parts of the olfac- tory organ is contracted and narrow, and the passages, a, b, are relatively short : they are, however, much prolonged by the accessory appendage, called ' trunk,' at the extre- Scction of Elephant's skull, showing nasal passage. .. r i i -i mity of which open the nos- trils (vol. ii. p. 282, fig. 162, n), and are as much expanded 1 ' Cornets infeiieurs,' De Bl. ; civ'. Gravigvadc=, p. 39. ORGAN OF SMELL IN MAMMALIA. m 1 ;"> 5 by the surrounding air sinuses, Avhich pervade every bone of the cranium. The bony nasal passage is continued in almost a straight line from the anterior aperture, a, to the posterior one, 1. The vomerine part of the septum, 1.3, extends from the pre- sphenoid about half-way to the anterior aperture. At the upper part of the cavity, so divided, the ethmoturbinals are situated, which are moderately plicated : the maxillary turbinal is, also, comparatively simple in character. In the Tapir the shorter proboscis terminates by a small pointed extremity between the nostrils. The snout is covered with hair to the base of the terminal appendage ; the hair on the upper part tending upward or backward, that on the sides toward the tip. The cribriform plate is not simply perforate, but is re- ticulate, with long radiating meshes, the latter closed by dura mater : it sends down curved lamellrc, sheathing the olfactory nerves. The ethmoturbinal consists of as many convolute divi- sions attached to, or continued from, those processes, in a pedun- culate way ; and each is perfo- rated bv many foramina through / / O which branches of the olfactory pass to the pituitary membrane. The maxillary turbinal is elon- gate and simply convolute. The nasal cartilages show the chief modification, the alar portions, fig. 155, n, being continued backward, expand- ing, and filling the peculiar grooves of the skull (vol. ii. p. 449) between the nasal bones and orbits, o : here the cartilages are semiconvolute, convex, and entire outwardly, excavated on the inner side, the cavity being continued by a groove into the nasal one at the sides of the outer aperture : from the character of the lining membrane, it may be regarded as an extension of ' Jacobson's fossa.' The ' levator rostri,' or raiser of the short proboscis, fig. 155, a, arises from the process of the lacrymal, runs in a fibrous sheath, couvero-ino- to its fellow, and is inserted into the upper or fore-side of the part which, together, they raise, or, acting separately, draw to their own side. A broader muscle, ( retractor labii,' Z>, from the same origin expands to its insertion at the side of the labial part of the base of the proboscis. Beneath this is the muscle, c-, which rising from the lower border of the lacrymal, spreads upon the p 2 Alinasal cartilage - and muscle.? of trunk, Tapir. xcni". 212 ANATOMY OF VERTEBRATES. 156 side of the proboscis, and is intimately connected with the ' orbi- cularis oris,' d d; c is the zygomatic, f the depressor anguli oris, y the buccinator. 1 The external nose of the Rhinoceros is com- bined with the upper lip and prolonged in a minor degree, but with a like arrangement of muscles, for prehensile purposes. The nose of the Horse is chiefly peculiar for the power of the dilating and contracting each nostril, such movements being sub- served by a lateral semilunar cartilage, fig. 156, /, ; by a de- pression or fold of contiguous skin, called ' false nostril ' in Hippotomy, and by the homo- logues of the muscles of the combined nose and lip of the Tapir. In fig. 156, a is the ( levator rostri ; ' b is the f re- tractor labii alasque nasi;' c is the muscle called ' transversus nasi,' in Hippotomy ; e is the zygomaticus ; f marks the in- sertion of a muscle, ' pyrami- dalis ' of Hippotomy, which arises by a slender tendon from the maxillary, and gliding be- neath the labial part of b, ex- pands to be inserted, fleshy, into the outer border of the nostril and contiguous skin- folds. The Horse is remarkable for the size of the rhinencephalon and the extent of the cribriform plate transmitting its nerves to Muscles of nostrils and upper lip, Horse. t ] ie noS e : they paSS Upon a series of about ten short longitudinal folds directed forward and a little downward^ forming the ( ethmoidal labyrinth' of Hippotomy, the upper larger division being the ' ethmoturbinal ; ' a longer, larger, more simply disposed plate, attached to both prefrontals and nasals, and chiefly descending from the latter bones, forms the ' nasoturbinal : ' beneath this is the ( maxilloturbinal,' of about the same vertical extent, and almost the same length. The bony septum contributed by the coalesced prefrontals, forms, superiorly, about one-fourth of the general partition : the vomer 1 xcin. pp. 20-26. ORGAN OF SMELL IN MAMMALIA. 213 extends, beneath it, along about three-fourths of the lower third of the septum, but subsides to a point ; the major part of the septum is gristly. In the Hippopotamus the nostrils are relatively small, promi- nent, wide apart, and are served by muscles which open and close them like the eyelids, besides protruding and retracting them. The accessory sinuses of the nasal chamber are very little developed. Their extent and size offer a great contrast in the Hog-tribe, in which the essential parts of the olfactory organ are also relatively larger and more complex. The rhinencepha- lon is large, with many nerves, and the cribriform plate of great extent : the ' labyrinthic ' part of the capsule attached to its under or outer surface forms nine or ten longitudinal, slightly diverging folds, fig. 153, q, the three or four uppermost of which coalesce to form the ethmoturbinal, which is long, slender, subconvolute, and attenuated to a fine point forward, ib. s. This figure gives an oblique view of the e labyrinth,' q, and ethmoturbinal, s, of the right and left sides. The nasoturbinal is of moderate length. The somewhat deeper and more con- volute f maxilloturbinal ' is shown at p : the accessory ( nasopa- latine ' fossa, at k. The pterygoid, f, bounding the posterior nasal opening is excavated and expanded above by a sinus continuous with those of the sphenoid, ?i. The accessory sinuses of the nasal chamber are very considerable in the Hog-tribe : the frontal ones (vol. ii. p. 468, fig. 315, 11, young Pig) extend back- ward over the calvarium to the occiput in the Boar: a structure well shown in the Babyroussa, No. 3346, * in which preparation the extension of the sphenoidal sinus (ib. fig. 315, f) into the base of the pterygoid is demonstrated, where it is divided into an external and internal compartment. In Phacochcerus the pterygo-nasal fossa is simple, and the frontal are almost separated from the parietal sinuses by the near approximation of the inner to the outer table of the skull. The pterygo-nasal fossa? are absent in Dicotyles. In all Suidce. the external nose is somewhat prolonged and truncate, the nostrils opening upon a naked disc : the cartilages of the nose form a complete tube, which is a con- tinuation of the bony nostrils, and near the end of the snout the cartilaginous septum becomes ossified, and forms the prenasal ossicle (ib. fig. 315, o). In the Ox the cribriform plate is relatively smaller and the olfactory nerves fewer than in the Horse : the labyrinthic part of the ethmoid consists of about six short narrow longitudinal 1 XLIV. p. 557. 214 ANATOMY OF VERTEBRATES. folds, most of which coalesce to form a larger and more simple ethmoturbinal than in the Horse; the nasoturbinal is very long and slender : the maxilloturbiual of much greater extent, espe- cially in vertical diameter : it terminates forward obtusely. In the Sheep the nasoturbinal is relatively deeper and less pointed than in the Ox. The nasal passages, from the lower border of their anterior outlet, traverse nearly three-fourths of the lonin- & tudinal extent of the long and slender skull of the Giraffe, fig. 157. The upper folds of the 'labyrinth' coalesce, and are pro- duced into the moderately long and deep ' ethmoturbinal ' a : the ' nasoturbinal,' I, deepest behind, is longer and more pointed 157 Left half of na*al cavily and lurbinals, exposed ia section of cranium ; Giraffe, xcvn' anteriorly than in other Ruminants ; the ( maxilloturbinal,' c, is large and deep, finely reticulate or perforate ; it is crossed by part of the vomer in fig. 157. The extent to which the air- sinuses communicating with the nasal chamber are extended is shown in this section, and noted in vol. ii. pp. 477, 478. The nasopalatine nerve entering the chamber below the fore-end of the ethmoturbinal receives some part of the olfactory filaments converging toward that end, then sends upward and forward a small branch to the nasoturbinal ; a larger branch downward and outward to the chamber-wall and its lining ; the main part being expanded on the long nasoturbinal. In the Ruminants a gradation may be traced in the extent of the glandular and, in health, moist part of the skin of the ex- ternal nose, from the Sheep, where it is a mere linear tract from the mid-furrow of the upper lip bifurcating to each oblique nostril, ORGAN OF SMELL IN MAMMALIA. 215 through the Roebuck, Fallow-deer, Red-deer, to the Ox, where it constitutes the broad naked muzzle. 1 The organ of smell in Carnivora mainly differs from that of hoofed Herbivora in the greater relative size and strength of the ethmoturbinal, the shorter, deeper, more massive and much more subdivided ' maxilloturbinal.' In the Lion the ethmoturbinal is of a pyramidal form, its broad base continued from the short labyrinthic part attached to the cribriform plate, its apex termi- nating forward, between the naso- and maxillo-turbinal. The o mesial surface of the ethmoturbinal shows numerous furrows, two of which are longitudinal and parallel with the upper margin of the bone, the others radiating from the lower part of the attached base : the lateral or outer surface is less complex and extensive ; but, on removing the outer layer, a series of con- centric curved folds are exposed. The ' nasoturbinal,' holding as in Ungulates the highest position, is an elongate cone, co- extensive with the roof of the nasal cavity and with its base opposite to the frontal sinus : the mesial surface shows a series of deep arched folds ; the lateral one seems more even, but when the peripheral lamella is removed a series of longitudinal folds of the bone is brought into view, beneath which are concentric folds -. o arched or curved in the opposite direction to those in the ethmo- turbinal. The maxilloturbinal is fusiform ; the hind end is at- tached to the outer wall of the nasal chamber below the middle of the nasoturbinal ; whence the bone rises and expands, crossing the anterior end of the ethmoturbinal, and again diminishing to its anterior and upper attachment behind the external bony nostril. From its position, therefore, the odorous atoms, in inspiration, must first impinge upon this bone, and the pituitary membrane is thicker and more vascular than on the other turbinals. Its mesial or septal surface presents one curved groove, parallel with and near to the lower margin of the bone : the outer surface has a like character. The more glandular part of the pituitary mem- brane is at the fore part of the floor of the nasal chamber, not occupying so deep a fossa as in Ungulates. The sources and distribution of the nervous supply corresponds with that noted in the Giraffe : the septal branches of the olfac- tory curve down toward the thickened base of the partition. In the Dog, the longitudinal folds of the ( labyrinth ' are about four, fewer in number but larger than in the Sheep : the aethmoturbinal is continued from the undermost and curves upward slightly to 1 This was pointed out to me by the estimable and justly famed \vater-colour artist and animal painter, ROBERT HILLS, F.L.S. 210 ANATOMY OF VERTEBRATES. the nasoturbinal as it advances : the maxilloturbinal is shorter, relatively broader and deeper, and much more extensively folded than in the Lion. This is the part of the olfactory organ that reaches the extreme of turbinal development in the Seal-tribe. In the large species dissected for the preparation, No. 1557, the maxilloturbinal is attached by its contracted extremities, the intervening enormously swollen mass is divided by a deep longi- tudinal furrow into two parts ; the free surface of which is singu- larly complicated by folds, radiating from both extremities of the bone and subdividing dichotomously. 1 These turbinals seem to block up the entry of the nasal respiratory passages, and must warm the air in arctic latitudes as well as arrest every indication from the effluvia of alimentary substances or prey. The nasotur- binals, in some Otariae, extend backward, with the nasal chamber, above the long rhinencephalic compartment of the cranium. In the Quadrumana the nasal chamber loses length and gains, but in less proportion, depth and breadth, from the Lemurs up to the Apes : the maxilloturbinal ceases to be suspended by its ex- tremities, and acquires a linear longitudinal attachment externally to a ridge on the maxillary wall of the nasal chamber. This tur- binal is divided into two chief parts lengthwise, in Lemuridce, where it is longest : the nostrils are here terminal, the anterior expan- sion of the septal cartilage curves outward and downward on each side, and, with a corresponding degree of curvation of the principal alar cartilage, gives a subconvolute form of nostril to most Strepsirhines. In the Aye-aye they describe a semi- circle ; and the nasal chamber by its shortness, depth, and pre- dominance of the ethmo- over the maxillo-turbinals exemplifies the quadrumanous affinities of the species. 2 In Platyrhine monkeys, the septal cartilage is remarkable for the transverse extent of its anterior terminal expansion between the nostrils, pushing them and their alar cartilages outward. In Catarrhines this expansion is much reduced ; and the nostrils are obliquely approximated. In both groups the nostrils cease to be ter- minal ; in a Bornean Douc ( Semnopithecus nasicus\ the nos- trils are produced upon an ill-shapen prominent subcylindrical nose. In the Gorilla each nostril is surmounted by a broad prominence, arching outward from a lower part impressed by a median furrow ; a deeper indent divides the nasal ala from the cheek : the aspect of the nostrils is forward and a little out- ward. The septal cartilage extends to the tip of the interalar prominence. 1 xx. vol. iii. p. 100. : cn'. p. 18, pi. viii. fig. 6. ORGAN OF SMELL IN MAMMALIA. 217 In Man the number of olfactory nerves varies from fifteen to twenty: after traversing the cribriform plate, they divide into two chief sets, ( septal ' and ( turbinal,' and ramify between the periosteum and the pituitary membrane before terminating on the latter. The septal nerves, fig. 158, , are about twelve in number, are quickly resolved into brushes of filaments, which unite together to form 159 plexuses, and send off branches forming 158 Branches of the olfactory and nasopalatine nerves on the septum of the nose. xciv. Alar cartilages, human tiose, xciv". finer plexuses, traceable to near the base of the septum. The posterior fourth of the septal membrane is chiefly supplied by the nasopalatine nerve, b. The ' turbinal ' or labyrinthic olfactory nerves are more numerous, rather smaller, and more plainly anastomotic in their course over the upper and middle ttirbinals, lying in grooves of the former, and extended chiefly upon the inner and lower front of the midturbinal ; a few combine with that part of the nasopalatine which supplies the lower part of the middle turbinal. The lower turbinal is almost exclusively sup- plied by a branch of the ( nasopalatine.' The main charac- teristic of the human organ of smell is the prominence of the fore-part of the chamber, having the nostrils on its lower surface, and constituting the feature emphatically called the f nose,' figs. 159, 161. The formative fold of integument is supported by eleven cartilages, of which one is medial, the others lateral, in live pairs. The medial or ( septal ' cartilage, fig. 160, is usually triangular, with three unequally curved margins : the upper one, 2)8 ANATOMY OF VERTEBRATES. IfiO Septal cartilage, xciv' 161 n, is fixed iii the groove of the ' perpendicular plate of the ethmoid,' the lower border, b, fits into the front groove of the vomer; the anterior border, c, extends from the nasal bones, where it is thickest, as at 2, d, and grows thinner down toward the apex of the nose. The varying proportions and form of the septal cartilage mainly govern the shape and prominence of the nose : it is least developed but thick- est in the Negro and Papuan races. The lateral cartilages vary in size and shape, the upper one, fig. 159, a, is triangular, continuous in front with its fellow, where they are closely connected with the tipper half of the anterior border, fig. 160, c, of the septal cartilage. The largest of the ( alar ' or e pinnate ' cartilages, fig. 159, b, is bent upon itself, almost surrounding and go- verning the shape of the nostril : it is movably connected with the lower and outer part of a. To the outer and hinder apex of the carti- lage by is joined the first of the three small cartilages, c, d, e, which sup- port the posterior convex part of the 4 ala ' or wing of the nose. The flex- ible fibrous tissue connecting these o elastic cartilages allow of the move- ments of the parts to be readily pro- duced, and the muscles are accord- ingly feeble. The ( pyramidalis nasi,' fig. 161, c, is continued from the medial portion of the ' frontalis,' fig. 28, f f which descends over the upper part of the nose to the cellular tis- sue covering the cartilage, a, and thence onward to combine o o y with fibres of the 'triangularis nasi,' fig. 161, e, and fig. 29, n. The ' leA^ator labii superioris alajque nasi ' is shown at dd, fig. 161 ; in the degree in which the alar is distinct from the labial portion, or has been distinctly exercised, the wings of the nose can be ex- Muscles of human nose, xciv ORGAN OE HEARING IN MAMMALIA. 219 paneled independently of any other movement of the face. The 6 depressor alae nasi,' ib. f, arises from the outer border of the sockets of the canine and contiguous incisor : the fibres ascend to the alrc, many of them arching over the outer and back pro- minence of the nostril. The 4 depressor septi,' ib. k, is detached from the upper part of the e orbicularis oris,' fig. 29, oo, the fibres converging; from each side toward the nasal septum. The ~ O * small triangular patch of pale fibres, fig. 161, g, is the ' com- pressor narium minor : ' the larger quadrilateral muscle, h, is the 6 levator alas proprius.' In races, like the Mincopies of the Andaman Islands } who scent the ripeness of indigenous fruits, moving the thick alae of their squab nose, as they explore their dark forests for this purpose, the nasal muscles may be expected to be well and instructively developed. 216. Organ of Hearing.- -The advance in this sense-organ in the mammalian class is seen in the extension of the cochlea, fig. 162, /, into coils suggesting the name ; in the greater propor- tion of the perilymph ; in the ossification of the cartilages between the stapes and tympanum forming the ' mal- leus,' and commonly also the "Mucus;' and in the presence, save in most swimmers and bur- rowers, of an external ear or conch, served by muscles for various movements to catch the sound. Besides the cochlea, the labyrinth, fig. 162, includes, as in other Vertebrates, the 0geeoU8 ]aljvrillth of the semicircular canals, c, d, e. and the interme- k ' ft side - Huiuan > ac SlXc diate space or ' vestibule,' a, by which they now communicate with the cochlea. The semicircular canals form a smaller proportion of the labyrinth in Mammals than in lower Vertebrates ; they retain, however, their posterior position to the vestibule and cochlea. The larger opening in the bony wall of the labyrinth is called, from its shape in Man, the ( foramen ovale,' or, from its situation in the labyrinth, ' fenestra vestibuli,' fig. 162, a: it is closed by the base of the stapes. A smaller ( round aperture,' ib. b, is called ' fenestra cochlea?,' because it forms the terminal orifice by which one of the turns of that part, ' scala tympani,' would open into the tympanum, were it not naturally closed by membrane. A depression in the petrosal or bony case of the labyrinth receives the facial and acoustic nerves, and terminates in a cul-de- sac, one division of which gives passage to the facial, fig. 165, k', the others receive divisions of the acoustic nerve, and transmit 1 xxxvn". 220 ANATOMY OF VERTEBRATES. 163 The labyrinthic cavity of the right side, magnified two diameters, Human, xcviv. them, by sieve-like plates, to the labyrinth; an anterior main one, ib. ?, going to the cochlea, and posterior ones, ib. g, m, supplying the vestibule and semicircular canals. The labyrinth is lined by a delicate membrane closing, as it passes, the fenestra tympani, whence it is plainly continued into the cochlea, and completes the spiral septum of that part : con- tinued over the vestibule, the lining membrane is applied to the base of the stapes which closes the ' fenestra vestibuli,' and it lines the semicircular canals. This membrane also extends along two very narrow canals continued from the labyrinth to the exterior of the petrosal, where it passes into the peri- osteum or dura mater of that part. One of the canals com- mences at the vestibule, at /?, fig. 163; the other from the tympanic f scala ' of the cochlea, at v : the serous fluid of the labyrinth passes through these canals to the general arachnoid receptacle of the cere- bral serosity, and they were ac- cordingly termed ' aqueducts,' and distinguished as ' vestibular ' and ' cochlear.' Minute blood- vessels are continued along both canals ; but their constancy and their relation as the intercommunicating medium between the acoustic and cranial serosity indicate a function which justifies the precision with which they have been described by Cotugno. 1 The anthropotomical ( aqueducts ' show the last trace of that com- munity, so extensive in fishes (vol. i. fig. 227), in the differentiation of the cranial from the otocranial cavities. The mammalian cochlea consists of a spiral tube, fig. 163, d, r, t, usually describing two turns and a half, and narrowing toward the apex, the vaulted roof of which forms the cupola,' fig. 164, c. The internal wall of the cochlear spire and the space it includes form the ( modiolus,' ' columella,' or hollow central pillar, ib. i, 2, which, from the wider sweep taken by the first turn, is broadest below. Here enters the trunk, ib. , a, of the cochlear division of the acoustic nerve, and the foramina by which its fibrils pene- trate the spiral canal extend along a part of the modiolus called ' tractus spiralis foraminulentus.' The tube of the cochlea is divided into two passages or ' scalar ' by a delicate plate of bone, fig. 163, q, q, attached to the inner or modiolar wall of the turns, and projecting freely into their cavity toward the outer wall : the 1 xcv. ORGAN OF HEARING IN MAMMALIA. 221 164 c 7 I Section of Cochlea, parallel with its axis, niagn. xcvi". lining membrane extends from this plate to the outer wall, fig. 164, d, e, and completes the separation of the two scake. The attach- ment of the base of the ' lamina spiralis ' is not solid, but indicates its constitution by two confluent layers, which here separate and intercept the minute channel called ( canalis spiralis modioli.' Towards the apex of the cochlea the spiral plate becomes free, and forms the part called ' hamulus,' fig. 164, 7. Here the two scalar intercommunicate, as shown by the bristle in fig. 164, which emerges above at the opening termed ' helicotrema,' ib. 8 : the apical part of the spiral lamina is formed by an onward extension of the lining membrane of the cochlea, bounding the up- per part of the columellar canal called < infundibulum,' ib. 2. In the section here exhibited the lower, 5, is the tympanic, the upper, c, the vestibular, division of the whorl divided by the partition, />, e, which is thus seen to be formed by the osseous plate supporting the nerve-filaments, b, the layer of membrane lining the tympanic scala, 5, and that lining the vesti- bular scala, 6 ; the two coalescing beyond the bone, and becoming thickened at e. where they a^ain v O pass into the parietal lining. The cochlea is essentially a develop- ment of the petrosal capsule im- mediately related to the bone of the head and its vibrations. The membranous labyrinth, fig. 165, retains, in Mammals, its common vertebrate character, extending through the semicircular canals and vestibule, but not beyond the part of the latter whence the cochlea is prolonged to its mam- malian extent : the sacculus, ib. f, retains the homologue of the otolite of that part in fishes and reptiles ; the second otolite, e, is also commonly present in the body of the vestibule : both are in 165 Membranous labyrinth, with nerves. Magnified, xcvi". V2-2 ANATOMY OF VERTEBRATES. the condition of pulverulent aggregates of combined carbonate and phosphate of lime, the latter in greater proportion in Mammals than in Fishes : the particles are held together by a mucous tissue. The membranous labyrinth has a ciliate inner surface, and contains a thinner * endolymph ' than in fishes : it is suspended in the common serosity of the bony labyrinth, which is distin- guished as ( perilymph/ Taking a retrospect of the course of the ear-organ, the primitive, constant, and essential clement is the i sacculus,' fig. 165, e,f, with its otolites, which receive the proportion of the nerve-supply not resolved into the pulpy lining of their bag : this simple condition obtains in Cephalopods. 1 In the Myxine something like one bent canal, and in the Lamprey two, are continued from the sacculus : in all higher Vertebrates the three semicircular canals are established ; but in most fishes they float, as shown in vol. i. p. 342, fig. 227, in the common serosity of the cranium ; their special bony cases, intercepting so much of the arachnoid fluid as now forms the ( perilymph,' are subsequently developed : finally is added the complex cochlea, into which the primitive mem- branous labyrinth is not extended. In fishes, where the acoustic nerves are affected by vibrations of the endolymph propagated from the cranium or the body gene- rally, the otolites are large, and usually of crystalline density. In air-breathers the sonorous vibrations of the atmosphere are more directly received : they first strike upon a membrane set in a frame and stretched across the opening of an air-chamber, like a drum. In Mammals the ( membrana tympani ' is more delicate than in Reptiles, and, with few exceptions, is concave outwardly. Sound is usually collected into a conch, the hollow of which can be directed to its source. The medium of acoustic communi- cation between the drum-membrane and the labyrinth under- 1G6 goes also, in Mammals, that instructive course of ossification and development which converts the avian columella and its cartilages into the chain of little ~ bones called ( otosteals.' These, after the external ear, are the seat of the chief modifications of the or^an in the o present class. They retain, in Mam- malia, the names suggested by their Human otosteal*. magn. xcvii". S ^ a P G in Man, VIZ. < StapCS,' fig. 166, C, 1 incus,' B, and i malleus,' A : a small epiphysis between B e and c a, when separate, is the f orbiculare ' 1 Civ. p. 294, and note. OCXLIX. p. 619. ORGAN OF HEARING IN MAMMALIA. Tympanum and eustachian tuiir XCVIII". Human, nat. M 168 or ' lenticular ' ossicle. To maintain an equable pressure on both sides of the membraiia tympani, and facilitate the movements of the otosteals on each other, atmospheric air is admitted into the cavity, as in other air-breathers, by the tube called 'eustachian,' fig. 167, , and is then continued by a course of about an inch and a half to the ear-drum, where it rather suddenly expands : in the subcutaneous part of its course the walls are strengthened by a few longitudinal carti- lages with elastic connections, allowing of slight changes in length and disposition ; but the walls are in contact throughout most of the narrow part of the tube. The ear-drum is concave exter- nally in DelphinidcR and Physeteridce ; but in a Balcenoptera Hunter found it projecting with an unusual degree of convexity into the dilated inner termination of the meatus. The density of the osseous tissue of the tympanic bone, ib. 35 and wider opening than in the badger : the incus is relatively small. In the wolverine (Gulo) the malleus is perforated near the orio-in of the process ; repeating a character presented in some birds by its cartilaginous homologue. In the otter (Lutra vulgaris} the malleus, fig. 176, B, is similarly perforated; the stapes is small, but adheres to the musteline type of the bone and is more widely open than in Seals. In the civets the stapes is triangular, its base oval, the branches thick and grooved on the O ' C5 inner side : the crura of the incus are short and very divergent. In Canis the stapes, ib. D, is subelongate, with the apex small, the base oval : the intercrural space is large. The handle of the malleus is grooved lengthwise. The stapes of the hyrena has a slightly convex and longish oval base ; the crura of the incus are short : the malleus is rather curved, with a short subcompressed handle. The ear-conch is large and long, without any fold of the external border : the tympanic is less inflated than in Feiis. The cochlea is longer and more prominent in the dog than in the cat. In this type-genus of Carnivora the acoustic capsule and labyrinth are small, especially in the large species ; but the tympanic cavity is expanded in all felines into a notable ' bulla ' at the base of the skull, formed chiefly by the tympanic, which, after framing the drum-membrane, forms an oval external orifice, deeply seated in the narrow space between the mastoid and zygoma. The stapes is a longish triangle, widely open, with the apex truncate and the base oblong, fig. 176, E, Tiger; it is shorter in the small Felines. The crura of the incus are short and subequal; the body of the malleus is broad and long; its handle of moderate length, and, in some, terminally expanded. The conch is short, usually rounded, broad and widely open ; relatively largest in the smaller species ; and distinguished in the lynxes by the apical tuft of long hairs. The otosteals in Quadrumana, fig. 177, quickly approximate to the characters of those in Man, ib., Homo : the stapes in Chiromys has a shorter and broader summit ; its base is firmly wedged into the foramen ovale. With the other otosteals it is proportionally larger than in true lemurs, bearing relation to the great develop- ment of the outer ears. These are large in all Lemuridce : the tragus and antitragus are well marked in Stenops, but instead of anthelix there are two prominent and subparallel plates. The vestibule is shorter, and the cochlea closer to the semicircular canals in the Aye-aye than in Man. In the Lemuridce the com- mencement of the cochlea is wide, and its axis is parallel with a line drawn from the fore end of the ampulla of the upper semi- 236 ANATOMY OF VERTEBRATES. circular canal, and meeting the latter just before its junction with the hinder semicircular canal. The stapes in lemurs is a more equilateral triangle, and the perforation is less than in monkeys : the incus has a longer and larger body in proportion to its crura : the malleus has a shorter process, fig. 177, A. In (Y/Wcr, ib. ii, the stapes gains in length, but not much in vacuity : the crura of the incus are still short, and the extensions 177 Lemur. Cebus. Cercojiithecus. Otosteals, Quadnmiana and Man. Homo. of the malleus are short in proportion to the mass articulating with the incus. The tympanum is large ; the external meatus short and very wide. In catarrhine monkeys, ib. C ( Cercopi- thecus sab&us) and in apes a nearer approach is made to the proportions and shapes of the human otosteals. There is a wider range of diversity in the external ear than in the more essential parts of the organ. In the nocturnal Aye-aye, in which the conch is relatively largest, there is a beginning of the helix above the meatal fossa, but the rest of the margin is thin and unfolded : the tragus is not very prominent, the anti- tragus is better marked : a low fold represents the ( lower crus ' of the anthelix, the upper one and the rest of that fold are wanting. It is only in the orangs and chimpanzees that the parts defined in the human auricle are represented. The free margin is reflected to form a ' helix,' but not to the same degree as in Man : the f anthelix,' beginning above with both ( upper ' and ' lower ' crus, is continued to the antitragus ; both scaphoid navicular fossa? are defined, as well as the cavity of the concha and the tragus : the lobulus is not pendant as in Man. In the chimpanzee ( Troglodytes niger] the external ear is larger abso- lutely than in the great gorilla ( Troglodytes Gorilla^. In all the figures of the otosteals previously given the stapes is drawn at right angles to its natural position, in which only a fore- shortened view of the bone could be had, as in fig. 178, where it is shown with its base a applied to the ' fenestra ' of the vestibule. ORGAN OF HEARING IN MAMMALIA. 237 Osseous labyrinth aiid otosteals, Human ; inagn. xcvui" . Of the three semicircular canals the shortest, c, has a nearly hori- zontal position : the other two are more vertical : the upper one rises at the convexity of its curve, d, above the level of the upper surface of the petrosal : it is that which, with its arch-area, is most free in many lower Mammals. The lower vertical canal, e, unites by its upper extre- 178 mity with the contiguous one at / ; the common opening of which is shown at m, fig. 163. Each of o the semicircular canals ex- pands at one extremity ; but this is more marked in the membranous canals, fig. 165, where the dilata- tions, a, b, c, are termed ' ampulla? : ' the bony ca- nals are wider in propor- tion to the membranous ones in Man than in most Mammals, and consequently the peri- lymph is more abundant. This is seen in fig. 179, which repre- sents the osseous labyrinth 1 79 laid open, with the mein- branous labyrinth in situ of the human ear. Of the latter the part occupying the vestibule is divided into the f common sinus,' i, and the ( sacculus,' / ; each contains a mass of otolithic powder, k, m, re- ceiving filaments of the acoustic nerve : other brushes of nerve filaments go to the ampul lary ends of the semicircular canals : the opposite non-dilated ends communicate with the ( common sinus ' either singly, at h, or by the conjoint termination y. The different positions of the three canals and the different directions in which their Left osseous labyrinth laid open, with membranous labyrinth and nerves ; magnified. Human, xcvu". 238 ANATOMY OF VERTEBRATES. Nerves of ampulla; and ' sinus communis;' magn. Human, xcix". 181 B respective waves of sound must strike upon the rich supply ot nerves at the ampullary ends, may have relation to the power of appreciating the locality of the source of sound, or the di- rection in which it arrives. The branch, fig. 180, y, to the ' com- mon sinus ' spreads thereon in a radiated expanse : the branches, o, p, to the ampullae of the upper, , and horizontal, b, canals, form a bifurcate enlarge- ment, p, upon their outer surface. When the ampulla is laid open, as in fig. 181, the nervous fork is seen to protrude and push in a slightly curved eminence of the membrane, ib. A, upon which and the adjacent part of the ampulla the delicate ner- vous fibres resolve them- selves into a kind of retinal pulp, ib. C. The septal plate of the cochlea has lent itself to a more favourable or distinct view of the termination of the acoustic fibrils. Fig. 182 Terminations of nerves in ampullae, magn. Human. XCIX "- shows the cochlear nerve, isolated. If a small bit of the spiral plate, fig. 183, A, be magni- fied, as at B, the filaments, b, are seen, as they diverge upon the osseous part, to sub- side or flatten on ap- proaching the middle tract, and there to anas- tomose in loops, c ; the neurilemma, d, being continued on to blend with the membranous part of the spiral plate. The human tympanic cavity, fig. 184, is formed by the petrosal,the mas- toid, and the tympanic bone: in the dry skull ; t 182 The cochlear nerve, magn. xcvi" ORGAN OF HEARING IN MAMMALIA. 239 communicates with the labyrinth by the foramen ovale, b, and fora- men rotundum, c ; with the exterior of the cranium by the foramen ]sr? auditorium externum : A TC ^sss^:. but all these apertures are closed by membrane in the recent state. The other communications are with the breathing pass- age, back of the nose, or pharynx, by the eusta- chian tube, fig. 167, a t b, c, whereby air is con- veyed into the tympa- num, and thence passes into the mastoid cells. On the petrosal wall of the tympanic cavity is specified the f promon- tory,' a, between the openings, b, c, the pyramid, d, the eminence of the e fallopian aqueduct,' e, and the groove, f, for the internal ligament of the malleus. The movements of the membrane closing the foramen ovale, Z>, Termination of cochlear nerve, more highly magn. (A. uat. size), xcvi-. 184 185 The nner wall of the tympanum, xcvii". Suuamosal and tympanic bone with the membrane. Human fretus. xcvii". are brought into relation with those of the membrane closing the o o outer auditory opening by the chain of ossicles called ( otosteals.' The f membrana tympani ' is fixed in a groove of a bony frame which is so far ossified as to form an incomplete ring, at the third month of human foetal life ; at the sixth month it begins to coa- C5 lesce with the squamosal, fig. 185, and then to grow outward, forming the wall of the bottom of the auditory meatus, fig. 188, g, the lower part of which is the last to be completed. The drum, fig. 186, consists of a ( proper membrane,' with an inner layer 240 ANATOMY OF VERTEBRATES. contributed by the lining of the tympanum, and an outer layer by that of the auditory passage. The proper membrane, moreover, is divisible into two layers, an outer one consisting of fibres radiating from near the centre, and an inner, thicker, less distinctly fibrous layer, but indicative of a contrary disposition of such fibres. Membrana tympani and malleus, nat. The COHSpicUOUS radiating fibres pass si/t-: Human, a outer, 6 inner view. , ., p i irom the circumterence 01 the mem- brane to be fixed to the handle of the malleus. They show no characters of voluntary muscular fibre. Anthropotomy distinguishes the following parts of the otos- teals : - -in the hammer, 'malleus,' fig. 166, A ; a, head; b, arti- cular surface (adapted to b of the incus) ; c, neck ; d, handle ; c, short process ; f, long process : this latter is the most con- stant, and is called simply the ( process ' in comparative anatomy ; sometimes also ( Rau's process,' from the describer of its true shape and flattened end in Man : in the anvil, ' incus,' B ; , body ; b 9 articular surface ; c, short crus ; d, long crus ; e, lenticular process, epiphysis, or ossicle : in the stirrup, ' stapes,' D ; , head ; />, neck ; c, anterior crus ; d, posterior crus ; r>, the base. The head of the malleus is lodged in the roof of the tympanum above the upper margin of the membrane, and sends its ( handle ' down to near its centre, as seen from without at a, from within at b, fio\ 186. The body of the incus lies in the upper and back part of the tympanum ; its articular surface is directed forward, the joint with the malleus being a synovial one, with articular car- tilage and a fibrous capsule : the short crus is directed backward towards the mastoid cells ; the long crus descends almost parallel with the handle of the malleus, to articulate by means of the lenticular process with the head of the stapes, fig. 178. Savart's experiments ' show that the malleus participates in the oscillations of the tympanic membrane ; that they are propagated to the incus and stapes, and thus to the membrane of the fenestra ovalis. Two muscles, probably subserving volitional impulse through their proper nervous supply, act upon the otosterals ; and from vibrations of the drum-membrane to which those bones are attached, they may be excited to act, also, automatically. The * musculus interims mallei,' or ' tensor tympani,' fig. 167, e, arises from the eustachian process of the alisphenoid, and from a groove in the bony part of the eustachian tube, and passing backward forms a slender tendon, which enters the tympanum, bending at 1 c". ORGAN OF HEARING IN MAMMALIA. 241 nearly a right angle, and is inserted into the handle of the malleus below the long process. By the action of this muscle the handle is drawn inward and forward, and the membrane attached to the handle is also drawn inward and is stretched. Besides the tension to which the membrana tympani is thus subjected, the base of the stapes is forced against the vestibular fenestra in consequence of the movement communicated by the head of the malleus to the incus, which tends to press inward the long extremity of the latter. The second muscle is the ' stapideus,' fig. 167, f: it arises from a groove in the ' pyramid,' fig. 18-i, d: it is inserted into the posterior and upper part of the head of the stapes by a slender tendon, which issues by the aperture in the summit of the pyramid, and proceeds downward and forward to its termination. The first effect of the action of this muscle will be to press the posterior part of the base of the stapes against the vestibular fenestra : at the same time the long branch of the incus will be drawn backward and inward, and the head of the malleus being, by this movement of the incus, pressed forward and outward, its handle will be carried inward, and the membrana tympani thus put on the stretch. On the other hand, the contraction of the ' tensor tympani ' depresses the stapes and increases the tension of the fenestral membrane. The cessation of muscular action restores all the vibratile membranes to their state of indifference. The incus, by its firm connection with the mastoid cells, its inter- mediate position, and having no muscle inserted into it, must be more limited in motion than the other two bones. The stapideus muscle receives a nervous filament from the facial nerve. The tendinous insertion of the stapes is usually the seat of ossification. These muscles have no homolo', is chiefly cartilaginous in the rest of its extent, but is membranous above and behind, and there perforated by the orifices of the ceru- minous follicles, o, p. The canal has an oval area, is about an inch and a quarter in length, and is lined by a continuation of the skin of the auricle. This skin becomes more delicate as it approaches the osseous part of the passage extremely so where it is continued 011 the outer surface of the membrana tympani. The skin of the auditory passage is covered with fine hairs, and these become developed at the outlet into long defensive cilia or ear-lashes. The ' fflandulae ceruminosae ' are small round or oval bodies of o a brownish-yellow colour, and very vascular. They are im- bedded in the areola3 presented by the dense cellular tissue which connects the skin of the auditory passage to the subjacent cartilage or bone. The ear-wax, cerumen, is, as is known, a thick orano-e-coloured or yellowish-brown viscid substance, of an o +> extremely bitter taste, and somewhat aromatic odour. \Vhen first secreted, it is a thin, yellowish, milky fluid. It is an accessory defence against the entry of insects into the meatus. The ear- O / drum closes the meatus obliquely from above downward and inward ; the bony part, light. The vesti- bular part of the labyrinth may be inferred to detect the presence and intensity of sound, especially as conveyed through the external ear and tympanum. It has been conjectured and argued that the semicircular canals are concerned in forming a judg- ment of the direction of sounds. The cochlea receives those sounds which are propagated through the bones of the head, and is conjectured to be the medium of the perception of the pitch of notes, and of the timbre or quality of sounds. The tympanum 246 ANATOMY OF VERTEBRATES. affords a non-reciprocating cavity for the free vibration of its membrane and of the otosteals : it also renders the labyrinth independent of atmospheric vicissitudes. The otosteals conduct vibrations from the tympanic membrane to the vestibular one, and, under the influence of the muscles, regulate the tension of botli these and of the cochlcar fenestra, so as to protect the ear against the effects of sounds of great intensity. The external ear and meatus are collectors and conductors of vibrations, and the former assists in enabling us to judge of the direction of sounds. 217. Organ of Sight.- -A. Eyeball. The organ of sight, like that of smell, is wanting in a few Mammals, the eyeball beino; reduced to the size and condition of the ' ocellus ' in Am- O blyopsis, and to its simple primitive office of taking cognisance of light, a filament of the fifth aiding the remnant of a proper optic nerve. The moles, especially the Italian kind, Talpa cceca* and mole-rats, exemplify this condition, in which, as in Spalax typhlus, the skin passes over the ocellus without any pal- pebral opening, or loss of hair. The eyeballs are very small in the allied genus Bathyergus, fig. 174, and other rodent bur- rowers : they acquire the largest absolute and proportional size in the Ruminant order. In no Mammal is bone developed in the sclerotic : in most a special ca- vity, called f orbit,' is fashioned in the facial part of the skull to give lodgment to the eye-ball. One sees least indication of it in the blind quadrupeds above noted and in the ant-eaters : it is deepest, best defined, and most completely walled in Man. In all Mammals with the eye developed for sight, properly so called, we recognise, as in the diagrammatic section, fig. 193, the fibrous capsule, a, called ( sclerotic coat,' the transparent fore part, b, called l cornea ; ' the vascular tunic, c, called ' choroid coat,' becoming thickened, at d, by the so-called e ciliary ligament,' from which the ' ciliary processes ' are, as it were, reflected back- ward upon the capsule of the lens,/: while the movable curtain, or ' iris,' is continued onward into the space between b and f, leaving a central opening, called 'pupil,' for the admission of 193 Diagrammatic section of Mammalian eye. c\" OKGAN OF SIGHT IN MAMMALIA. 247 light. The choroid, c, is lined by the expansion of the optic nerve called ' retina/ which extends to the ' ciliary processes,' and is kept outstretched by the f vitreous humour ' contained in the cells of the delicate membrane called ' hyaloid,' which restrains its forward advance beyond the ( crystalline humour ' or lens, f. The space in front of this body is occupied by the ' aqueous humour,' and is divided by the iris into an f anterior ' and ' pos- terior chamber.' The rays of light admitted by the cornea and pupil are slightly refracted in traversing the aqueous humour, and are sub- ject to a greater degree of convergence in passing through the 194 Diagram of course of luminous rays iu traversing the humours of the eye. denser lens, fig. 1 94 ; when, striking the retina at the back of the globe, they there depict the image of the visual object, in- verted. In crepuscular and nocturnal Mammals (Pteromys, Aye-aye, Lemur) the cornea gains in size and convexity and the iris in breadth ; the latter being capable of admitting many rays through a very wide pupil, which also it can completely close against the glare of noontide. The convexity of the lens is concomitantly increased, and it approaches the spherical form most nearly, in bats and nocturnal rodents. The vitreous humour is less in pro- portion to the crystalline and aqueous humours in such eyes. In aquatic Mammals, on the contrary, the cornea hardly projects (seals, whales), and there is little aqueous humour ; here, also, the convexity of the lens is in excess, fig. 195, d. In most diurnal and terrestrial mammals, the eyeball is subspherical, the cornea slightly projecting at the fore part, as forming part of a smaller sphere than the rest of the globe. The lens retains much of the proportions shown in fig. 194. 248 ANATOMY OF VERTEBRATES. In the Ornithorhynchus the eyeball is small and spherical; the sclerotic fibre-cartilaginous, the cornea flabby, the retina thick : there is no trace of pecten or marsupium : the lens is two lines in transverse diameter, one line in antero-posterior diameter ; the anterior surface is nearly flat, the posterior very convex. The choroid is black, without a tapetum lucidum ; the pupil is circular. The anatomy of the eye offers no peculiarity illustrative of the affinities of the Marsupialia or of any other speciality in their economy save the nocturnal habits of the majority of the order. It is in relation to these habits that the lens is large and convex, the iris broad, the pupil round and very dilatable, and the cornea correspondingly large. The eye is relatively large in the swift- moving, far-ranging Kangaroos : I found the dark pigment on both the inside and outside of the choroid ; the ciliary processes are long: the lens is proportionally large. In the dead Kan- garoo the radiated muscle of the iris is much contracted, and the o pupil widely open. The eye is small in Didelplds virginiana ; the pupil is round : the lens very convex. The Insectivora have small eyes : the moles least of all. In a great pipe-toothed shrew (Solenodon) one foot in length, exclusive of tail, the palpebral opening does not exceed three lines, and there is no distinction between orbit and temporal fossa. Bats have the smallest eyes of all volant Vertebrates. In Rodents the size of the eyeball bears relation to the extent and swiftness of locomotion, and is greatest in Jerboidce and Leporidce. The position of the eyes is always lateral, and by the prominence of the cornea they are susceptible in these timid quadrupeds of re- ceiving the image of a pursuer. In the hare and other rodents the retina seems to expand from the divisions of a cleft termina- tion of the optic nerve, within the eyeball. The pupil is round in most Rodents : in a dead Agouti it was a horizontal ellipse. In the squirrel the ante-retral diameter of the eyeball is to the transverse as 11 to 12 : in the hare it is as 23 to 25. J In all the order Bruta the eyes are relatively small : in the sloths the contracted pupil is a vertical slit. In Cetacea the eyes are small, especially in relation to the bulk of the larger kinds : and the essential part of the organ is still less, owing to the thickness of the sclerotic, fig. 195, a, a, and this increases from the cornea, b } backward to the long, 1 A table of these dimensions of the eye in different Vertebrates will be found in xii. iii. p. 390 ; also in cvi". ORGAN OF SIGHT IN MAMMALIA. 249 Section of the eye of a Whale. infundibular canal for the optic nerve, f. Outwardly the eye- ball is subspherical ; but, in the section figured, the contour of the cavity containing the vitreous humour, e, and lens, d, presents an ellipse, with the long axis transverse : in a Balcenoptera of 65 feet in length, this axis measured 2^ inches, and the shorter axis 2 inches : the posterior curve is regular ; but, toward the cornea, the sclerotic turns in quickly, c, flattening the fore part of the eye : the distance between the fore part of the sclerotic and the bottom of the eye beinor but 14 inches. In */ o shape the cornea is a longer ellipse than the eyeball, and the upper border is more curved than the lower : it is thinner at the centre than the circumference, and is soft and flaccid in the dead whale. The choroid has a silvery or bluish white hue on the inner surface : the darker pigment is limited to the ciliary processes and back of the iris. In a mysticete whale ( Bal&na) the cellulosity connecting the choroid with the sclerotic was of a light brown hue : the darker pigment extends from the ciliary processes a little way upon the choroid : and in both kinds of w r hale is so disposed as to absorb the rays of light and prevent them being a second time reflected so as to disturb the spectrum on the back of the retina. Of the numerous minute folds which constitute the ciliary zone every third, fourth, or fifth is en- larged, and produced forward to form a wrinkled corrugated process about three lines long, compressed and terminating obtusely : the intermediate shorter processes are of varying length ; the long ciliary processes are about seventy in number, in Bal&noptera. The peripheral radiated contractile fibres of the iris, and the central circular ones, are conspicuous on the back part of that curtain in whales : the front surface shows the wavv vessels radiating from arterial canals which surround the margin of the pupil which is transversely elliptical. Four equidistant canals in the thick sclerotic give passage to the long ciliary arteries and the vorticose veins : the two arteries which advance in the direction of the long axis of the pupil terminate in a canal bordering the pupil a little way from its margin : the wavy branches radiate from this canal, and are prominent on the 250 ANATOMY OF VERTEBRATES. anterior surface of the iris. The quantity of the aqueous humour is small : the lens, d, is subspherical, flatter in front than behind. The nucleus is seen in the posterior half and the surrounding la- mina) are reflected inward and backward toward the middle of the anterior surface of the nucleus, leaving a funnel-shaped cavity in front of it which is filled by less dense substance. In Hyperoodon the pupil is transversely oblong with a moderate projection of the upper margin, reminding one of the skate's pupillary curtain (vol. i. p. 334). In the Grampus the choroid presents a greenish tinge : in the Porpoise it is a bluish white. In both, the pupil resembles that of Hyperoodon. The retina is thick. In the Seals the sclerotic is chiefly remarkable for the sudden thinning at the part corresponding Avith the ciliary zone ; it is moderately thick both in front and behind : the cornea is thin and flabby. The muscles of the eye-ball being inserted into the an- terior part of the sclerotic may shorten the axis of the eye and bring the lens nearer to the back of the globe, thus adapting it to vision in air and water. In the Sirenia the eye is very small. In a Rhytina of 25 feet in length the eye-ball was but 1 inch in diameter : it is about 1 inch in diameter in the Dugong : the pupil is circular. The eye of the Elephant is about 2 inches in diameter, re- minding one of that in the Whale by its small relative size : there is likewise an unusual thickness of fibrous or sclerotic sub- stance at the entry of the optic nerve, and a similar extent of light-coloured tapetum within the choroid, which tapetum presents the fibrous type of structure: the pupil is round, the cornea is larger and more convex than in Cetacea. o In the Rhinoceros the eyeballs are of small comparative size ; in the Indian species which I dissected, 1 each measured in aiitero-posterior diameter one inch five lines, and in transverse diameter one inch three lines. Some dark-brown pigment lies under the conjunctiva for the extent of about a line from the circumference of the cornea : the same kind of pigment is also deposited upon the outside of the nictitating eyelid, and over a great part of the inner surface of the same part, covered of course by a reflection of the conjunctiva. The trunks of the vena? vorticosa? perforate the sclerotica half-way between the entry of the optic nerve and the edge of the cornea : their disposition, with the flocculent but somewhat firm connecting tissue of their radiating branches, presented that structure which most nearly resembled the figures given by Mr. Thomas of the parts he 1 v", p. 56. ORGAN OF -SIGHT IN MAMMALIA. 251 describes as ( processes having a muscular appearance, with the fibres running forwards in a radiated direction.' 1 On removino- C5 O the anterior part of the sclerotica, whilst the eye was suspended in spirit, both the vitreous humour and the lens rolled out ; and the capsule of the lens showed no particular mark of the inser- tion or fixation of the ciliary processes ; their impressions, in remains of pigmental matter, were perceptible on the anterior part of the ( canal of Petit.' The transverse diameter of the lens was six lines, the aiitero-posterior diameter four lines. The pig- ment was not confined to the inside of the choroid ; but in both Rhinoceroses dissected by me, I found on the outside of the chorion much loose cellular tissue, with dark pigment : this coloured flocculent tissue concealed at first the venas vorticose, even when injected. The sclerotica is one line thick at the back part of the eyeball ; and is thinnest near the middle of the ball, becoming thicker towards the cornea, which is two lines thick. The choroid adheres pretty strongly to the back part of the sclerotic, around the entry of the optic nerve, both by the enter- ing vessels and by the tenacity of its outer flocculent coat, especially where the vessels penetrate the sclerotica. There is no tape turn lucidum. The lower eyelid has a special depressor muscle. 2 The Tapir has a proportionally small eyeball. Of the Perisso- dactyle group the Horse has the largest eyes, in relation to its greater powers of locomotion. They are lateral, prominent, capable of directing against any object in the rear, without turn of the head, the outkick of the hind-leg. The cornea inclines to an oval figure, the larger end being toward the nose. The tape- turn is of a light blue colour/ and fibrous structure: the ciliary processes are long ; more numerous than in the ox : the pupil is transversely oblong, rather wider on the nasal side, with a few processes from the upper margin. In the Hog-tribe the cornea is oval, with the large end in- ternal, or toward the nose ; the sclerotic is thin ; the pupil is round ; the eyeball rather larger than the palpebral opening would indicate ; the inner figure of the choroid is of a shining chocolate colour in the common Hog, but much darker in the Babyroussa. The eyes in Ruminants are large, lateral; the transverse exceeds the fore-and-aft diameter of the eyeball. In the Ox the latter is to the transverse diameter as 43 to 49 ; in the sheep as 32 to 35. The ciliary processes are short in most, especially in some Antelopes : the retina extends far forward. 1 cvi", p. 157, pi, x. ; figs. 1-3. 2 v", p. 56. 252 ANATOMY OF VERTEBRATES. The tapetal layer is fibrous, extensive, of almost metallic bright- ness ; in most of a fine green colour ; in a few of a bluish tint, with certain portions, generally toward the bottom of the eye, white : in the Ox the tapetum occupies a broad transverse tract of the choroid. The pupil is transversely oblong, with the upper border somewhat festooned in the Camel, Ox, and Sheep. In the Garni vora the relative size of the eyes increases from the Bears to the Cats. The tapetal layer exists in most, and consists of obscurely nucleated cells. In the nocturnal Badger o it is silvery white ; in the Dog arid Wolf whitish, edged with blue ; in most felines of an amber, or golden, or greenish hue, with a lighter tract of crescentic form, curving round the lower part of the entry of the optic nerve. In the Lion, the greater extent of tapetum is below the nerve ; only a small portion above : the general form of the whole tapetum is broadly crescentic in Felines. In the small crepuscular Cats the pupil contracts to a vertical slit ; in the larger diurnal felines it is circular. The optic nerve penetrates more nearly the axis of the eyeball in Carnivores than in Ruminants : the ciliary folds are long, espe- cially in the Lynx, in which the retina does not reach the meridian of the eyeball : it is also very thin. In the nocturnal Quadrumana the main modifications of the eye- ball have been noted ; the large and prominent cornea, the unusu- ally convex lens, the broad iris and circular pupil, and the patch of tapetum, are well exemplified in the dissection of the eyes of Stenops gracilis, in xx, vol. iii. p. 158, no. 1706. I found also a delicate tapetum at the back of the eye in Chiromys ; but the light is less brightly reflected from the living eyes of the Aye- aye than from those of the slow Lemurs. The lens is almost spherical in Perodicticus. In no Lemurine has the retinal spot been found ; but there seems to be a minute fold or crease in its place. This spot, fig. 201, A, due to a thinning there of the retina, defined by a yellowish border, accompanied, usually, in the dead eye, with a slight crease, and situated in or very near the axis of vision, exists in the catarrhine Quadrumana as in Man. The sclerotic seems, in most, to be somewhat thinner than in Man and to take more readily the stain of the choroidal pig- ment after death. In no Quadrumana above the Lemurs is there a tapetum. The human eyeball is in some individuals a sphere ; in most the antero-posterior is rather less than the transverse dia- OKGAN OF SIGHT IN MAMMALIA. 253 meter. 1 The sclerotic, or ' tunica albuginea,' is of a fibrous structure, and so much as is visible at the fore-part of the globe forms the ( white of the eye : ' being thinner here than behind, the dark choroid appearing through it sometimes gives it a bluish tint; it resumes thickness near the cornea. This, fig. 193, b, forms the segment of a smaller sphere than the rest of the eye- ball ; it is perfectly transparent in the living eye, and consists of a proper tunic, a most delicate continuation of conjunctive mem- brane, fig. 207, , called by its describer Petit, ' canal godronne: ' the folds of the hyaloid in relation to the ciliary processes form the ( corona ciliaris,' ib. c. In the human crystalline lens the anterior V is to the posterior convexity as 4 to 3 : the transverse diameter is from 4 to 4J lines, the thickness or axis is about 2 lines. The degrees of convexity of both surfaces vary at different periods of life. In fig. 203, A shows the lens of a six-months' fretus, B, of a child of six vears, C, of an adult of middle age : after fifty A. Back of retinn, showing macula centralis and poms options. B. ' Jacob's membrane' reflected from the retina, cv". Vitreous limnour with hyaloid meml>rane and lens, showing the ' canal of Petit' aud corona ciliaris; magn. cv". ORGAN OF SIGHT IN MAMMALIA. '257 A Crystalline lens, human, at different ages ; nat. size. cv". 204 it becomes rather flatter and also firmer in texture. The density of the lens is not the same throughout, the surface being nearly fluid, while the centre scarcely yields to the pressure of the finger and thumb, especially in advanced life. The eye is thus rendered achro- matic. The specific gravity of the lens to water is as 10024 to 10000 : the re- fractive power of the centre of the lens is to that of water as 18 to 7. Brewster found the following; to be the refractive o powers of the different humours of the human eye, the ray of light being incident upon them from the eye : ( aqueous humour, 1-336; crystalline, surface 1'3767, centre 1-3990, mean 1-3839 ; vitreous humour, 1'3394. But as the rays refracted by the aque- ous humour pass into the crystalline, and those from the crys- talline into the vitreous humour, the indices of refraction of the separating surface of these humours will be, from the aqueous humour to the outer coat of the crystalline, 1*046(5; from the aqueous humour to the crystalline, using the mean index, 1*0353 ; from the vitreous to the outer coat of the crystalline, 1*0445 ; from the vitreous to the crystal- line, using the mean index, 1-0332.' If the lens with the capsule attached to the hyaloid membrane be placed in water, the following day it is found slightly opaque or opaline, and split into several portions by fissures ex- tending from the centre to the circumference, as in fig. 204, B. If allowed to remain some days in water, it continues to expand and unfold itself; and if then transferred to spirit and hardened, it may be unravelled by dissection, fig. 204, c, and its fibrous structure demonstrated. In Man and Mammals generally three septa diverge from each pole of the lens at angles of 120, the septa of the posterior sur- face bisecting the angles formed by the septa of the anterior sur- face : the fibres diverge from these septa as shown in fig. 205. The denticulated structure by which the fibres are laterally united, or interlock, is shown in vol. i. p. 333, fig. 217, in the crystalline lens of a cod. The human lens is inclosed in a transparent, firm, elastic capsule. A branch of the ' arteria centralis retinae ' VOL. III. 8 A, Crystalline lens, natural state; B, peripheral softer portion fissured by action of water; c, resolution of nucleus into fibres, magni- fied, cv". 258 ANATOMY OF VERTEBRATES. 205 attains the back part of the capsule, and ramifies richly thereon, in the foetus. The aqueous humour lodged in the chamber between b and /, fig. 193, has a refractive power very little higher than that of water; 100 parts consisting of 98'10 of water, 1-15 of chloride of sodium, and 0'75 of extractive matter soluble in water, with the merest trace of albumen : it is secreted by the membrane lining the chamber. B. Appendages of the Eye. The muscles moving the human eyeball are the four straight and two oblique ones. In lower Quadrumana a few fibres seem to be detached from the inner part of the origin of the recti to be inserted into the sclerotic nearer the entry of the optic nerve. This is the remnant of a stronger muscle, which in other Mammals, with few exceptions, surrounds the optic nerve, expand- ing, funnel-wise, as it ap- proaches the back of the eyeball : it is called the ( choanoid muscle,' or sus- pensor oculi, and is supplied by a branch of the sixth cerebral nerve. In Cetacea it is divided into four short mus- cles, paralleling the longer recti, but of greater breadth and almost continuous : they are inserted into the sclerotic behind the transverse axis of the eye-ball. The narrower and longer recti muscles expand to be inserted anterior to that axis. The superior oblique arising, with them, above the foramen opticum, has the course of its fibres changed, as usual, by a pulley at the upper and fore part of the orbit, but in passing through the sub- stance which serves as the trochlea, the muscle is only partially tendinous- and little diminished in diameter. The inferior oblique is long, and broad at its insertion. In the Rhinoceros the fasciculi of the .choanoid muscles have coalesced into two masses: in most quadrupeds they form a single f infundibular suspensor.' The cellular tissue is more or less condensed between the insertions of the choanoid and the fleshy parts of the recti muscles, and in Man between these Arrangement of fibres of lens, Mammal, ccxin. ORGAN OF SIGHT IN MAMMALIA. 259 and the eyeball, the recti perforating this layer or sheath before expanding to their insertions. The upper one, ( rectus superior,' directs the cornea upward, the ( rectus inferior ' downward, the e rectus externus ' outward, the f rectus interims ' inward or toward the nose ; the ( recti ' antagonising, or combining with, each other in all the degrees required to make the cornea assume any intermediate direction : they can thus produce the move- ments analogous to the ( circumduction ' of a limb ; in doing which the centre of the cornea describes a circle. For f rotation' of the eyeball, in which this corneal centre remains fixed as the fore end of an axis, the two muscles called ' oblique ' are added. In Mammals the ' superior oblique ' arises from the back part of the orbit with the recti, advances to the upper part of the rim, glides there through a tendinous pulley, returns toward the eye- ball, is reflected backward and outward beneath the rectus superior, and is inserted into the sclerotic between this muscle and the rectus externus. The inferior oblique takes its origin, in advance of the eyeball, from the orbital plate of the maxillary ; passes outward and backward beneath the ' rectus inferior,' and is inserted into the outer and back part of the sclerotic. The two oblique are so disposed as to act, when antagonising each other, in rotating the eyeball 011 its antero-posterior axis : when combining in action they tend to draw forward the eye, and thus antagonise the recti muscles collectively. The trochlear arrange- ment of the superior oblique is peculiar to the present class. As habitually antagonistic muscles have nerves from distinct sources, the rectus abductor is supplied by the ' sixth ' nerve, the rectus adductor by the ' third.' The superior oblique, which opposes the inferior one in most movements, is supplied by the 6 fourth ' nerve. As the depression of the eyeball can be per- formed by the superior oblique if the downward motion be directed by the lateral muscles, it suffices that it should have the same separate nerve (fourth) for that motion as for antagonising the inferior oblique, which, like the upper, lower, and inner recti, is supplied by the ' third nerve.' l In Cetacea the eyelids are represented by a continuous circular fold of the skin, leaving a round opening in front of the eye with a narrow margin unprovided with eyelashes. This ' palpebral ' opening is closed by an orbicular muscle or sphincter, and is expanded by four broad, thin, almost continuous muscles (in the Porpoise). The ( tunica conjunctiva,' fig. 195, y, lines the circular 1 For Hunter's excellent remarks on ' the use of the Oblique Muscles/ see xciv. p. 24. VOL. in. *s '2 200 ANATOMY OF VERTEBRATES. eyelid, and is reflected upon the eyeball, near its middle. At the line of reflection are the orifices of a zone of ' Meibomiaii ' follicles : an aggregate of somewhat more complex ones at the inner side of the eyeball represents a f Harderian ' gland. There is no true lacrymal gland, nor any ( third ' or nictitating lid. The presence of this eyelid distinguishes the Sirenia from the Cetacea ; l and the Harderian gland is more distinctly developed. In Seals the circular eyelid is supplied by four dilators and a sphincter, as in Whales ; but an external groove at the inner can thus indicates the division of the horizontal eyelids : the nictitating membrane is well developed and the Harderian gland at its base is large. In the Elephant the ' third ' or vertical eyelid is supported by a flat, slightly curved cartilage, which becomes thinner as it is attached to the concave free margin : the Harderian is continued as in Cetacea, from a group of smaller mucous glands, which have many excretory orifices upon the margin of the third eyelid, but its principal duct terminates upon the inner surface near the base of that lid. There is a special f nictitator ' muscle, the fibres of which pass at first over the base of the membrane in a curve, then form an angle to include the extremity of the nictitating cartilage, which is consequently moved in the diagonal of the contracting forces, and pushed forward and outward over the front of the eyeball. In the Rhinoceros the lower eyelid has a depressor muscle. The Harderian gland is large in the Hog-tribe ; its duct opens upon the lower part of the inner surface of the membrane : it co-exists with a ( caruncula lacrymalis.' There is a small lacrymal gland the duct of which opens upon the inner surface of the upper eyelid : the margin of this is provided with a row of stiff, unequal cilia, beneath which are orifices of the ( Meibomian glands.' In most Ungulates the base of the third eyelid is buried in a fatty and fibrous substance. In the Sheep a large 4 caruncula ' co- exists with the Harderian and lacrymal glands. The upper eyelid has cilia in all Ruminants. The margins of the lids and the conjunctiva are charged with black pigment in the Giraffe ; and the cilia of the upper lid are very long. The eye is protected, in the Ornithorhynchus, by a cartila- ginous plate continued from the upper part of the orbit, com- parable with the palpebral plates in the crocodile. Both the water Monotreme and the Echidna have a well developed membrana nictitans : there are also an upper and a lower eyelid, each of which has its proper apertor muscle. In Marsupials, the 1 CXTIT". p. 28. ORGAN OF SIGHT IN MAMMALIA. 281 206 Harderian gland and the retractor oculi co-exist, as usual, with the nictitating eyelid. This is largely developed, and the conjunctiva covering its free margin is stained black. Beneath the upper eyelid, in the Kangaroo, there is a cartilaginous ridge having the conjunc- tiva reflected over it. There are no palpebral cilia in Didelphis. The Harderian gland subserves the movements of the third or nictitating lid, and with the choanoid muscle, are present in all quadrupeds up to the Quadrumana. In these, as in Man, the third lid is reduced to a small fold, fig. 206, ^, at the inner canthus, within and projecting a little be- yond the vascular protu- berance called ( caruncula lacrymalis,' ib. f: the Har- derian gland ceases to be developed : the true lacry- mal gland at the upper and outer part of the orbit, fig. 209, k, /, is large. In fig. 206 the orifices of the ' tar- sal ' or f meibomian ' glands are shown at , CL. In Man and Quadrumana the upper of the two horizontal lids is the largest and most movable, contrary to the case in most lower Mammals. The fibrous tissue within that fold of skin is now condensed to form a ( tarsal cartilage,' largest and most conspicuous in the upper lid, of which it forms the basis : its straight and thick border consti- tutes the ciliary margin. In the lower lid the so-called t cartilage ' is hardlv more developed than it - Section of eyelids showing extent of conjunc- 1S in both lids Of quadrupeds. Ihe tive membrane and ducts of lacryrnal gland. The eyelids of the left side opeued. xcvni". 207 CX". meibomian follicles extend into the fibrous (lower lid) or fibrocartilaginous (upper lid) tissue. The muscle closing the lids is the f orbicularis palpebrarum,' fig. 29, o. The upper lid is raised by a special muscle, ' levator pal- pebras superioris,' which extends from the upper border of the optic foramen, to the tarsal fibro-cartilage. The lower lid on the relaxation of the s orbicularis' which draws it up, falls down by its own elasticity : rarely in Mammals has it a proper 2G2 ANATOMY OF VERTEBRATES. 208 Lacrymal gland, left side. ex". depressor. The outer border of the ciliary margin of both lids is provided, in Man, with eye-lashes, fig. 207, the orifices of which, when plucked out, are shown at h, fig. 206. In this figure b is the f outer can thus,' c the ' inner canthus,' d lacrymal papilla or 'punctum 5 of the upper lid; e, the same of the lower lid ; /*, the lacrymal caruncle ; ^7, the semilunar fold representing the ' third eyelid,' and now forming the bottom of the ' lacus lacrymalis ' within the fissure of the inner can thus ; i, the eye- brow. In the section of the outer parts of the eyelids, in fig. 207, is shown the line of reflection of the con- junctive membrane upon the eyeball, y, at the upper and outer part of which line open the 9 to 12 orifices of the ducts of the lacrymal gland, into which bristles have been inserted. The gland, fig. 208, consists of an upper por- tion #, a, which is lodged in the shallow depres- sion at the outer side of the roof of the orbit, and a lower thinner portion, b, b, which is a looser aggregate of lobules extending into the substance of the upper eyelid. The fluid contributed by the lacrymal and meibomian glands to the conjimctival cavity,, after being spread by the winking movements of the lids over the front of the eyeball, is carried along the groove formed by the margins of the closed lids to the o inner canthus, and is there im- bibed by the ' puncta lacrymalia,' fig. 209, , a. From each of these orifices a canal is continued, ascend- ing in the upper, descending in the lower lid ; in both, then, bending at an acute angle and converging to a long dilated receptacle, f, 'g, called * lacrymal sac.' The large blind end, e, is directed upward ; the sac gradually contracts, h, to the ( nasal duct,' i, which opens into the infe- rior meatus, fig. 152, k, of the nose. In all Mammals with divided or horizontal eyelids there is a similar provision for carrying off the waste lubricating fluid of the eyeball. In Man, in whom the true lacrymal gland is relatively largest, its peculiar secretion - the tears - when emotionally secreted in excess, overflows the palpebral groove. 209 Lacrymal apparatus, Human, ex". ORGAN OF SIGHT: *IN MAMMALIA. 26 J fC. Parallel between eye and ear. The author of ' the. excellent articles, xcvii" and ex'' has drawn a parallel between the eye and ear which, in the main, appears to me to express justly the ' serial homologies' of the parts of those sense-organs. I include, how- ever, the consideration of the cavities in which they are respec- tively lodged. The ( otocrane ' parallels the ( orbit.' The homo- logy is masked by the deeper situation of the former, its commu- nication rather with the interior than with the exterior of the cranium, and its more frequent coalescence with the fixed bony sense -capsule which it includes. In some Mammals, however, that capsule retains its primitive and typical distinctness, and can be removed from the otocrane. 1 This is, then, seen to be formed by the exoccipital and alisphenoid, the mastoid, the tympanic, and, in Mammals, the expanded and intercalated squa- mosal. The primitive bony nuclei of the capsule which appear round the fenestra rotunda, on the outer end of the upper vertical semicircular canal, and on the middle of the hinder vertical semicircular canal, extend to form the bony labyrinth, and are wholly independent of the centres from which the ossification of the mastoid or otaer otocranial bones begins. The addition of bony matter envelopes in various degrees the first formed part of the capsule, called ' bony labyrinth,' and constitutes, therewith, the ' petrosal.' This capsule of the ear corresponds with the sclerotic in the eye ; which, in many Vertebrates, becomes the seat of ossification, and in some (Cetacea, e.g., fig. 195, ) is thickened as much out of proportion to the nervous and vascular parts of the essential organ it contains, as is the petrosal. The orifice by which the optic nerve enters the eye-bulb answers to the foramen audi- torium internum. The membranous labyrinth answers to the parts of the eyeball within the sclerotic. The delicate vascular external tissue of the labyrinth, frequently exhibiting pigment- specks, answers to the choroid, the expansions of the acoustic nerves to the retina, the endolymph to the vitreous humour. The fluid in the space between the sclerotic and choroid, including the aqueous humour, represents the perilymph. Wharton Jones compares the f lens ' to the ' otolites.' 2 If we compare the conjunctival space in front of the eyeball with the tympanic cavity, and the duct therefrom leading to the nose with the eustachian tube, then the anterior opening of the sclerotic will answer to the fenestra vestibuli, and the membrane closing- it, or cornea, to that which closes the fenestra. In mammals the open movable eyelids seem very remote analogues to the 1 XLIV. p. 557. 2 xcvn". p. 562. 264 ANATOMY OF VERTEBRATES. external membrane closing the tympanum : but they are super- added developments to the true serial homologue of the tympanic membrane, shown in Reptilia, vol. i. p. 338, 339, fig. 220 ; and which disappears or blends with the later added developments of integument with special cartilages, muscles, and glandules, and which truly parallel the ' pinna ' of the ear. In the eyelids, the meibomian follicles repeat the ceruminous ones, and the eyelashes, the Qilia which guard the entry to the meatus auditorius. Wharton Jones compares the muscles of the eyeball to those of the otosteals, and I concur, with him, in accepting the opinion of Weber as to the special relation of both to their respective Organs of Sense, and as to their being parts superadded to the elements of the ver- tebral skeleton. But I believe that the divergence of functions so governs the development of special motive organs and ossicles as to remove the ground for safely or usefully homologising such parts, and I refrain from going beyond the serial repetitions in the eye and ear which are above indicated. 265 CHAPTER XXIX. DENTAL SYSTEM OF MAMMALIA. 218. General characters of the Teeth. The present class in- cludes a few genera and species that are devoid of teeth ; the true ant-eaters (Myrmecophaga], the scaly ant-eaters (Manis), and the spiny monotrematous ant-eater (Echidna), are examples of strictly edentulous Mammals : Ornithorhynchus has horny teeth ; the whales (Balcena, Balcenoptera) have transitory embryonic calcined teeth, fig. 219, succeeded by whalebone substitutes, fig. 217, in the upper jaw. The, female Narwhal seems to be edentulous, but has the germs of two tusks in the substance of the upper jaw-bones : one of these so remains ; the other becomes developed into a large horn-like weapon in the male Narwhal, fig. 220, A, and suggested to Linnaeus the name, for its genus, of Monodon : but the tusk is never median, like the truly single tooth on the palate of the Myxine ; and occasionally both tusks are developed. In Hyperob'don the teeth are reduced in the adult to two in number, whence the specific name, H. bidens ; but they are very small and confined to the lower jaw. Ziphius has two teeth of functional size and shape, one in each ramus of the lower jaw ; and this is perhaps a sexual character. The Delphinus griseus has five teeth on each side of the lower jaw : but they soon become reduced to two. The Marsupial genus Tarsipes is remarkable for the paucity as well as minuteness of its teeth. The Elephant has never more than one entire molar, or parts of two, in use on each side of the upper and lower jaws, to which are added two tusks, more or less developed, in the upper jaw. Some Rodents, Hydromys, e. g., have two grinders on each side of both jaws, which, added to the four cutting teeth in front, make twelve in all ; the common number of teeth in this order is twenty ; but the hares and rabbits have twenty-eight teeth. The sloth has eighteen teeth. The number of teeth, thirty-two, which characterises man, the apes of the Old World, and the true Ruminants, is the average one of the class Mammalia ; but the typical number is forty-four. The examples of excessive number of teeth are presented, in the order Bruta, by the Priodont 266 ANATOMY OF VERTEBRATES. Armadillo, which has ninety-eight teeth ; and in the Cetaceous order by the Cachalot, which has upwards of sixty teeth, though most of them are confined to the lower jaw; by the common porpoise, which has between eighty and ninety teeth ; by the Gangetic dolphin, which has one hundred and twenty teeth ; and by the true dolphins (Delphinus\ which have from one hundred to one hundred and ninety teeth, yielding the maximum number in the class Mammalia. Where the teeth are in excessive number, as in the species above cited, they are small, equal, or sub-equal, and of a simple conical form ; pointed, and slightly recurved in the common dolphin ; with a broad and flattened base in the Gangetic dolphin ; with the crown compressed and expanded in the porpoise ; com- pressed, but truncate, and equal with the fang, in Priodon. The compressed triangular teeth become coarsely notched or dentated at the hinder part of the series in the great extinct cetaceous Zeuglodon. The simple dentition of the smaller Armadillos, of the Orycterope, and of the three-toed Sloth, presents a difference in the size, but little variety in the shape of the teeth, which are subcylindrical with broad triturating surfaces ; in the two-toed Sloth, the two anterior teeth of the upper jaw are longer and larger than the rest, and adapted for piercing and tearing, fig. 215. Teeth are fixed, as a general rule, in all Vertebrates. In Mammals the movements of the teeth depend on those of the jaw-bones supporting them, but appear to be independent in the ratio of the size of the tooth to the bone to which it is attached : the seemingly individual movements of divarication and approxi- mation observable in the large lower incisors of the Batkyeryus and Macropus, 1 are due entirely to the yielding nature of the symphysis uniting the two rami of the lower jaw, in which those incisors are deeply and firmly implanted. In Man, where the premaxillaries early coalesce with the maxillary bones, where the jaws are very short, and the crowns of the teeth are of equal length, there is no interspace or ( diastema ' in the dental series of either jaw, and the teeth derive some additional fixity by their close apposition and mutual pressure. No inferior Mammal now presents this character; but its im- portance, as associated with the peculiar attributes of the human organisation, has been somewhat diminished by the discovery of a like contiguous arrangement of the teeth in the jaws of a few extinct quadrupeds ; e. g., Avoplothcrium, Nesodon, and Dichodon^ 1 xxv. \ol. i. p. 285. '- ci.xxx. fig. 130. DENTAL SYSTEM OF MAMMALIA. 267 The teeth in Mammals, as in the fore^oin^ classes, are formed ~ o * by superaddition of the hardening salts to pre-existing moulds of animal pulp or membrane, organised so as to insure the arrange- ment of the earthy particles according to that pattern which cha- racterises each constituent texture of the tooth, together with a ' O course of vitalising plasma through its tissue. The complexity of the primordial basis, or ' matrix,' corre- sponds, therefore, with that of the fully-formed tooth, and is least remarkable in those conical teeth which consist only of dentine and cement. The primary pulp, fig. 129, i* 9 which first appears as a papilla rising from the free surface of the alveolar gum, is the part of the matrix which, by its calcification, constitutes the dentine. In simple teeth, the secondary, or enamel pulp, covers the dentinal pulp like a cap; in complex teeth it sends processes into depressions of the coronal part of the dentinal pulp, which vary in depth, breadth, direction, and number, in the different groups of the herbivorous and omni- vorous quadrupeds. The dentinal pulp, thus penetrated, offers corresponding complications of form ; and, as the capsule follows the enamel pulp in all its folds and processes, the external cavities or interspaces of the dentine become occupied by enamel and cement the cement, like the capsule which formed it, being the outermost substance, fig. 237, c, and the enamel, ib. e, being in- terposed between it and the dentine, ib. d. The dental matrix presents the most extensive interdigitation of the dentinal and enamel pulps in the Wart-hog, Capybara, and Elephant. The matrix of the mammalian tooth sinks into a furrow, and soon becomes inclosed in a cell in the substance of the jaw-bone, from which the crown of the growing tooth extricates itself by exciting the absorbent process, whilst the cell is deepened by the same process, and by the growth of the jaw, into an alveolus for the root of the tooth. Where the formative parts of the tooth are reproduced indefinitely, to repair, by their progressive calcifi- cation, the waste to which the working surface of the crown of the tooth has been subject, the alveolus is of unusual depth, and of the same form and diameter throughout, figs. 215 and 216, except in the immature animal, when it widens to its bottom or base. In teeth of limited growth, the dentinal pulp is reproduced in progressively decreasing quantity after the completion of the exterior wall of the crown, and forms, by its calcification, one or more roots or fangs, which taper to their free extremity. The alveolus is closely moulded upon the implanted part of the tooth ; and it is worthy of special remark, that the complicated form of 268 ANATOMY OF VERTEBRATES. socket, fig. 256, which results from the development of two or more fangs, is peculiar to animals of the class Mammalia. In the formation of a single fang, the activity of the reproduc- tive process becomes enfeebled at the circumference, and is pro- gressively contracted within narrower limits in relation to a single centre, until it ceases at the completion of the apex of the fang, which, though for a long time perforated for the admission of the vessels and nerves to the interior of the tooth, is, in many cases, finally closed by the ossification of the remaining part of the capsule. When a tooth is destined to be implanted by two or more fangs, the reproduction of the pulp is restricted to two or more parts of the base of the coronal portion of the pulp, around the centre of which parts the sphere of its reproductive activity is progressively contracted. The intervening parts of the base of the coronal pulp adhere to the capsule, which is simultaneously calcified with them, covering those parts of the base of the crown of the tooth with a layer of cement. The ossification of the sur- rounding jaw, being governed by the changes in the soft but highly organised dental matrix, fills up the spaces unoccupied by the contracted and divided pulp, and affords, by its periosteum, a surface for the adhesion of the cement or ossified capsule covering the completed part of the tooth. The matrix of certain teeth does not give rise, during any period of their formation, to the germ of a second tooth, destined to succeed the first. This, therefore, when completed and worn down, is not replaced ; all the true Cetacea are limited to this simple provision of teeth. In the Armadillos, Megatherioids, and Sloths, the want of germinative power, as it may be called, in the matrix, is compensated by its persistence, and the consequent un- interrupted growth of the teeth. In most other Mammals, the matrix of certain of the first developed teeth gives origin to the germ of a second tooth, which displaces its predecessor and parent. All those teeth which are so displaced are called temporary, de- ciduous, or milk teeth, fig. 293, d i, d 1-4. The mode and direc- tion in which they are displaced and succeeded, namely from below upward in the lower jaw, in both jaws vertically, are the same as in the crocodile ; but the process is never repeated more than once in the present class. A considerable proportion of the dental series is thus changed ; the second, or permanent teeth, ib. i i-p } 2-4, having a size and form as suitable to the jaws of the adult as the displaced temporary teeth were adapted to those of the young animal. Those permanent teeth, ib. m \-m 3, which DENTAL SYSTEM OF MAMMALIA. 269 210 assume places not previously occupied by deciduous ones, may be regarded as a continuation of that series, and are posterior in their position ; they are generally the most complex in their form. The successors of the deciduous incisors and canines differ from them chiefly in size. The successors of the deciduous molars may differ likewise in shape, in which case they have less complex crowns than their predecessors. The ' bicuspids ' in Anthropotomy, fig. 258, p 3, p 4, and the corresponding teeth called ' premolars' in lower mammals, fig. 293, p 2-4, illustrate this law. The Mammalian class might be divided, in regard to the succes- sion of the teeth, into two groups the Monophyodonts, or those that generate, as a rule, one set of teeth, and the Dipliyodonts, or those that generate two sets of teeth. 1 The Monophyodonts include the Monotremata, Ceta- cea and Bruta ; all the other orders are Diphyodonts. The teeth of Mammalia, espe- cially of the Diphyodonts, have usually so much more definite and complex a form than those of fishes and reptiles, that three parts are recognised in them : the fang or root (radix , fig. 210, /) is the inserted part ; the crown (corona, ib. &) is the exposed part ; and the constriction which divides these is called the neck (cervix, ib. n). The term 'fang' is properly given only to the implanted part of a tooth of re- stricted growth, which fang gradually tapers to its extremity. Those teeth which grow uninterruptedly, fig. 236, have not their exposed part separated by a neck from their implanted part, and this generally maintains to its extremity the same shape and size as the crown. It is peculiar to the class Mammalia to have teeth implanted in sockets by two or more fangs, figs. 256, 293 ; but this can only happen to teeth of limited growth, and generally characterises the molars and premolars : perpetually growing teeth require the base to be kept simple and widely excavated for the persistent pulp? figs. 215 and 216. In no mammiferous animal does anchylosis 1 Vol. ii. p, 268. Section of human molar tooth, niagu. 270 ANATOMY OF VERTEBRATES. of the tooth with the jaw constitute a normal mode of attach- ment. Each tooth has its particular socket, to which it firmly adheres by the close co-adaptation of their opposed surfaces, and by the firm adhesion of the alveolar periosteum to the organised cement which invests the fang or fangs of the tooth. True teeth implanted in sockets are confined to the maxillary, premaxillary, and mandibular or lower maxillary bones, and form a single row in each. They may project only from the premax- illary, as in the Narwhal, or only from the lower maxillary as in the Ziphius ; or be apparent only in the lower jaw, as in the Cachalot ; or be limited to the superior and inferior maxillaries, and not present in the premaxillaries, as in the true Ruminants and most Bruta. Mammalian teeth usually consist of hard un vascular dentine, fig. 210, d, defended at the crown by an investment of enamel, ib. e, and everywhere surrounded by a coat of cement, ib. c. The coronal cement is of extreme tenuity in Man, Quadrumana, and terrestrial Carnivora ; it is thicker in the Herbivora, espe- cially in the complex grinders of the Elephant, fig. 289, and is thickest in the teeth of the Sloth, Megatherium, Dugong, Walrus, and Cachalot. Vertical folds of enamel and cement penetrate the crown of the tooth in most Rodents and Ungulates, characterising by their various forms the genera ; but these folds never converge from equidistant points of the circumference of the crown towards its centre. The teeth of Bruta have no true enamel ; this is absent likewise in the molars of the Dugong and of the fully de- veloped teeth of the Cachalot. The tusks of the Narwhal, Walrus, Dinothere, Mastodon, and Elephant, consist of modified dentine, which, in the last two great proboscidian animals, is properly called f ivory,' and is covered by cement. The Dolphins and Armadillos present little variety in the shape of the teeth in the same animal, and this sameness of form is characteristic of Monophyodonts ; subject, like the successional character, to such exceptions as are exemplified in Choloepus didactylus, fig. 215, and in Dasypus 9-cinctus, the milk-teeth of which are figured in cxxxn", p. 254. In most other Mammals particular teeth have special forms for special uses : thus the front teeth, from being commonly adapted to effect the first coarse division of the food, have been called cutters or incisors ; and the back teeth, which complete its com- minution, grinders or molars : large conical teeth, situated behind the incisors, and adapted by being nearer the insertion of the biting muscles, to act with greater force, are called holders, fearers, laniaries, or more commonly canine teeth, from being well TEETH OF MONOPHYODONTS. 271 developed in the dog and other Carnivora, although they are given, likewise, to many vegetable feeders for defence or combat ; e. g., Musk-deer. Molar teeth, which are adapted for mastica- tion, have either tuberculate, or ridged, or flat summits, and usually are either surrounded by a ridge of enamel, or are tra- versed by similar ridges arranged in various patterns. Certain molars in the Dugong, the Mylodon, and the Zeuglodon, are so deeply indented laterally by opposite longitudinal grooves, as to appear, when abraded, to be composed of two cylindrical teeth cemented together, and the transverse section of the crown is bilobed. The teeth of the Gtyptodon were fluted by two analogous grooves on each side, fig. 214. The large molars of the Capybara and Elephant have the crown cleft into a numerous series of com- pressed transverse plates, cemented together side by side. The modifications of the crown of the molar teeth are those that are most intimately related to the kind of food of the animal possess- ing them. Thus, in the purely carnivorous mammals, the prin- cipal molars are simple, trenchant, and play upon each other like scissor-blades. In the mixed feeding species, the working surface of the molars becomes broader and tuberculated ; in the insectivo- rous species it is bristled with sharp points ; and in the purely herbivorous kinds, the flat grinding surface of the teeth is com- plicated by folds and ridges of the enamel entering the substance of the tooth, the most complex forms being presented by the Elephants. 219. Teeth of Monophyodonts. A. Monotremata. The sub- stances serving for teeth in the Oriii- 211 thorhynchus are of a horny texture, consisting of close-set, vertical hollow O ' tubes, resembling the outer compact tissue of baleen or ' whalebone.' They are eight in number, four in the upper, and as many in the under jaw. The anterior tooth of the upper jaw is ex- tended from behind forward, but is low, very narrow, and four-sided. The corresponding tooth in the lower jaw, fig. 211, by is rather narrower, and retains longer its trenchant edge. At c5 O a distance from the anterior tooth, equal to its own length, is situated the horny Mandible and teeth > ornithorhyncus. molar, ib. c, which consists of a flattened plate of an oblong sub- quadrate figure. The corresponding tooth in the lower jaw is 272 ANATOMY OF VERTEBRATES. somewhat narrower, but of simple form. Each division or tubercle of the molar is separately developed, and they become confluent in the course of growth. According to the analysis of Lassaigne, 99-5 parts of the dental tissue of the Ornithorhynchus have the composition of horn ; this is hardened by 0-3 parts of phosphate of lime. The notice of the dental apparatus of the Monotremes ought to include mention of the two short and thick conical processes, fig. 212, g, Nl ','- u:"^ .tf-wvr f Tongue, lingvial teeth, and larynx of the Orni- thorhynchus. Section of lower jaw and teeth of the Orycteropus. Nat. size eye, are shown in fig. 213. The teeth are continued, solid, and of the same dimensions, to the bottom of the socket, and terminate in a truncate and undivided base. If each be viewed as an aggre- gate of teeth, as partially shown in fig. 247, vol. i., p. 396, it will be found that the component denticle has its base excavated by a conical pulp-cavity, as in other animals, and which is persis- tent, as in the rest of the order Bruta. The wide inferior aper- tures of these pulp-cavities constitute the pores observable on the base of the compound tooth of the Orycterope, and give to that part a close resemblance to the section of a cane. The canals to which these pores lead are the centres of radiation of the dentinal TEETH OF MONOPHYODOXTS. 273 tubes ; such denticles are cemented together laterally,, ib. c, slightly decreasing in diameter, and occasionally bifurcating as they approach the grinding surface of the tooth. The substance of the entire tooth thus resembles the teeth of the Myliobates and ChimtBroids among fishes, rather than any in the Mammalian class, in which it offers a transitional step from the horny dental substitutes, above described, to the true teeth. The teeth of the Orycteropus, when rightly understood, offer, however, no anomaly in their mode of formation. Each denticle is developed according to the same laws, and by as simple a matrix, as those larger teeth in other mammals which consist only of dentine and cement. The dentine is formed by calcifica- tion of the pulp, the cement by ossification of the capsule ; both pulp and capsule continue to be reproduced at the bottom of the alveolus, part passu with the attrition of the exposed crown ; and the mode and time of growth being alike in each denticle, the whole compound tooth is maintained thoughout the life of the animal. The augmentation in the size of the whole tooth, during the growth of the jaw, is effected by the development of new denticles, and a slight increase of size in the old ones, at the base of the growing tooth, which, in the progress of attrition and growth, becomes its grinding surface. The teeth of the Armadillo-tribe are harder than those of other species of Bruta, the unvascular dentine being present in greatest proportion, and forming the main body of the tooth ; it includes a small central axis of vascular dentine, and is surrounded by an extremely thin coating of cement. The numerous teeth in Priodon are of very small size and simple form, and are all referable to the molar series. They vary in number from twenty-four to twenty-six in each upper jaw, and from twenty-two to twenty-four on each side of the lower jaw, amounting to from ninety-four to one hundred in total number. The Armadillos of the sub-genus Euphractus, TVagler, are distinguished by having the anterior tooth, which is shaped like the succeeding molar, 214 implanted in the premaxillary bone. The two anterior teeth of the lower jaw being in advance of the premaxillary tooth, are, with it, arbitrarily held to be incisors. Some species of the extinct loricate genus, Glyptodon, surpassed the Rhinoceros in size, crown of tooth of great v M. . . . extinct Armadillo and the dentition was more complicated, and (Giyptodon ciavipesi. more adapted to a vegetable diet, than that of the small existing Armadillos. The osteo-dentine, fig. 214, o, occupied a larger VOL. III. T 274 ANATOMY OF VERTEBRATES. proportion of the centre of the tooth, and being harder than the dentine, d, or cement, c, rose upon the grinding surface, in the form of a ridge extending along the middle of the long axis of that surface, and in three shorter ridges at right angles to the preceding, at the middle of each of the three rhomboidal divisions of the tooth. Of the leaf-eating species of the order Bruta, very few, and these the most diminutive of the tribe, now exist. The following are the characters of their dentition, both recent and extinct :- Teeth implanted in the maxillary and mandibular bones, few in number, not exceeding -J: -J ; composed of a large central axis of vaso-dentine, with a thin investment of hard dentine, and a thick outer coating of cement : to these add the dental characters common to the order Bruta, viz., uninterrupted growth, and con- comitant implantation by a simple, deeply-excavated base. In the two-toed sloth (Cholcepus didactylus^llig.) the teeth, fig. 215, offer a greater inequality of size than has yet been observed in any other genus of Bruta ; the first of each series, i, in both jaws, which in the rest of the order is the smallest, here so much exceeds the others as, with its peculiar form, to have received the name of a canine. This tooth is separated by a marked interval from the other teeth, 2-5, es- pecially in the upper jaw, so that 1-1 above play upon the anterior part of those below, contrary to the relative position and mutual action of the true canine teeth in the Quadrumana and Carnivora. The teeth of the Megatherium, the most gigantic of the extinct quadru- peds of the Sloth tribe, are five in number on each side of the upper jaw, fig. 216, and four on each side of the lower jaw. They are deeply implanted with narrow intervals : each is exca- vated by an unusually extensive pulp-cavity, ib. p, from the apex of which a fissure is continued to the middle depression of the grinding surface of the tooth. The central axis of vaso-dentine, v f is surrounded by a thin layer of hard or unvascular dentine, d, and this is coated by the cement, c, which is of great thickness on the anterior and posterior surfaces, but is thin where it covers the outer and inner sides of the tooth. The vaso-dentine, v 3 fig. 238, Teeth of the two-toed Sloth (Chalcepus didactijlus). TEETH OF MONOPHYODONTS. '27.1 vol. i. p. 361, is traversed throughout by medullary canals, measuring -j-Vo ^ an mcn m diameter, continued from the pulp- cavity, and anastomosing in pairs by a loop, the convexity of which is turned towards the origin of the tubes of the hard dentine, t. 216 Section of upper jaw and teeth of the Megatherium. One-third nat. size. The cement, ib. c, is characterised by the size, number, and regularity of the vascular canals which traverse it in a direction slightly inclined from the transverse axis toward the crown of the tooth, running parallel to each other, and anastomose in loops, the convexity of which is directed toward the hard dentine. The tooth of the Megatherium offers an unequivocal example of a course of nutriment from the dentine to the cement, and reci- procally. All the constituents of the blood freely circulated through the vascular dentine and the cement, and the vessels of o each substance, intercommunicated by a few canals, continued across the hard or unvascular dentine. The minuter tubes, which pervade every part of the tooth, characterising by their difference of lensfth and course the three constituent substances, form one o * continuous and freely intercommunicating system of strengthening and reparative vessels, by which the plasma of the blood was dis- tributed throughout the entire tooth, for its nutrition and main- tenance in a healthy state. The grinding surface of the close-set molars of the Megatherium differs on account of the greater thickness of the cement on their VOL. ITT. *T 2 276 ANATOMY OF VERTEBRATES. anterior and posterior surfaces, from those of all the smaller Megatherioids, in presenting two transverse ridges, fig. 216, d\ one of the sloping sides of each ridge being formed by the cement, c, the other by the vascular dentine, v, whilst the unvascular den- tine, d, as the hardest constituent, forms the summit of the ridge like the plate of enamel between the dentine and cement in the Elephant's grinder. The great length of the teeth, and concomi- tant depth of the jaws, the close-set series of the teeth, and the narrow palate, are also strong features of resemblance between the Megatherium and Elephant in their dental and maxillary organisation. In both these gigantic phyllophagous quadrupeds provision has likewise been made for the maintenance of the grind- ing machinery in working order throughout their prolonged exis- tence : but the fertility of the creative resources is well displayed by the different modes in which this provision has been effected : in the Elephant, it is by the formation of new teeth to supply the place of the old when worn out ; in the Megatherium, by the constant repair of the teeth in use, to the base of which new matter is added in proportion as the old is worn away from the crown. Thus, the extinct Megatherioids had both the same struc- ture and mode of growth and renovation of their teeth as are manifested in the present day by the diminutive Sloths. C. Cetacea. Those Mammals which are properly called f Whales' have no teeth, but horny substitutes in the form of plates, termi- nating or fringed by bristles. Of these plates, called ( baleen ' and 217 Baleen-plates and Tongue of Piked Whale (Balcenoptera) ' whalebone,' fig. 217, b, the largest, which are of an inequilateral triangular form, are arranged in a single longitudinal series on each side of the upper jaw, situated pretty close to each other, depending vertically from the maxillary bones, Avith their flat surfaces looking backward and forward, and their unattached margins outward and inward, the direction of their interspaces TEETH OF MONOPHYODONTS. 277 218 a being nearly transverse to the axis of the skull. The subsidiary plates are arranged in oblique series internal to the marginal ones. Thus, if the upper jaw of one side of the skull of a Whale were bisected transversely, the flat surface of a series of the baleen- plates would be exposed, as in fig. 218, in which a is the superior maxillary bone, b the ligamen- tous gum, giving attachment to c the horny base and body of the chief baleen-plate, which termi- nates in d, the fringe of bristles ; e marks the smaller baleen-plates. The base of each plate is hol- low, and is fixed upon a pulp developed from a vascular gum, which is attached to a broad and shallow depression occupying the whole of the palatal surface of the maxillary and of the anterior part of the palatine bones, the Whale being thus, like the Echidna, an example of a mamma- lian animal, which may be said to have palatal teeth. The base of each plate is unequally imbedded in a compact sub-elastic sub- stance, b, which is so much deeper on the outer than on the inner side, as, in the new-born whale, to include more than one half of the outer margin of the baleen-plate. This margin is shown at c, fig. 218, and is continued down in a line dropped nearly vertically from the outer border of the jaws. The inner margin of each plate, d, slopes obliquely outward from the base to the extremity of the preceding margin ; the smaller plates decrease in length to the middle line of the palate, so that the form of the baleen-clad roof of the mouth is that of a transverse arch or vault, against which the convex dorsum of the thick and large tongue, fig. 217, , is applied when the mouth is closed. Each plate sends off from its inner and oblique margin the fringe of moderately stiff but flexible hairs, which project into the mouth. These present an obstacle to the escape of the small marine ani- mals, 1 for the prehension and detention of which this singular 1 Clio borealis, Limacina arctica, and small pelagic Crustacea. Section of Upper Jaw, with Baleen-plates, of a "Whale (Bahenoptera). 278 ANATOMY OF VERTEBRATES. modification of the dental system is especially adapted. The baleen-pulp is situated in a cavity at the base of the plate, like the pulp of a true tooth ; whilst the external cementing material maintains, both with respect to this pulp and to the portion of the baleen-plate which it develops, the same relations as the dental capsule bears to the tooth. According to these analogies, it must follow, that only the central fibrous or tubular portion of the baleen-plate is formed, like the dentine, by the basal pulp, and that the base of the plate is not only fixed in its place by the cementing substance or capsule, but must also^receive an acces- sion of horny material from it answering to the cement of true teeth. In Baloena mysticetus there are about 200 large marginal plates on each side, from 10 to 14, rarely 15, feet in length, and about 1 foot in breadth at their base ; these plates are overlapped and concealed by the under lip when the mouth is shut. In the Balanopterce or fin-backed whales, figs. 217, 218, the baleen-processes, e, internal to the marginal plates, are fewer and smaller than in the Balance ; the marginal plates, c, are more numerous, exceeding 300 on each side ; they are broader in pro- portion to their length, and much smaller in proportion to the entire animal ; they are also more bent in the direction transverse to their long axis. A thin transverse section of baleen, viewed with a low mag- nifying power, demonstrates that the coarse fibres, as they seem to the naked eye, which form the central substance, are hollow tubes with concentric laminated walls. When a high magnifying power is applied to such a section, the concentric lines are shown not to be uniform, but interrupted here and there by minute elliptical dilatations, which are commonly more opaque than the surrounding; substance, and which, like the radiated cells of true o * * bone, are probably remains of the primitive cells of the formative substance ; similar long elliptical opaque bodies or cells are dis- persed irregularly through the straight parallel fibres of the dense outer laminae of the baleen-plate. The chemical basis of baleen is albumen hardened by a small proportion of phosphate of lime. The Bal&nida, before they acquire their peculiar array of baleen-plates, manifest in their foetal a^e a transitory condition J. O v of a true dental system, abortive and functionless, but homologous with that which is normal and persistent in the majority of the order. In an open groove which extends along the alveolar border of both the upper and the lower jaws, there is a series of minute, conical, acute or obtuse, single or double, denticles, fig. 219, with TEETH OF MONOPHYODONTS. 279 hollow bases inclosing the uncalcified remains of a vascular pulp. In the foetus of a Balcenoptera, the jaws of which were about four inches in length, the groove of the upper jaw contained twenty-eight such teeth, that of the lower jaw forty -two : these disappear before birth. The foetal Whale exem- plifies the earliest stage of dental de- velopment in the higher Mammals, Trausitory den ticie s of roetai wiTaie retaining the open fissure which in them is rapidly closed. The great Bottle-nose or bident Whale offers a transitional grade between the true Whales and the typical Delphinidcs. The foetal denticles do not all perish, but two or three of the anterior pairs acquire a large size as compared with their transitory repre- sentatives in the Bal&nidcB and one of these pairs is long retained in the lower jaw, though functionless, and hidden by the gum. In the Narwhal (Monodon monoceros), two of the primitive dental germs at the forepart of the upper jaw proceed in their de- velopment to a greater extent than do those in the lower jaw of the Hyperoodon ; but every other trace of teeth is soon lost. The two persistent matrices rapidly elongate, but in the retrograde direc- tion, forming a long fang rather than a crown ; each tooth sinks into a horizontal alveolus of the prem axillary bone, or, rather, at the junction of the prernaxillary with the maxillary, and soon, by the forward growth of these bones, becomes wholly inclosed, fig. 220, , like the germs of the teeth of higher Mammals at their second stage of development. In the female Narwhal, the pulp is here exhausted, the cavity of the tooth is obliterated by its ossi- fication, further development ceases, and the two teeth remain concealed as abortive germs in the substance of the jaws for the rest of life. In the male, the matrix of the tooth in the left pre- rnaxillary, ib. b, continues to enlarge ; fresh pulp-material is pro- gressively added, which by its calcification elongates the base, protrudes the apex from the socket, and the tusk continues to grow until it acquires the length of nine or ten feet, with a basal diameter of four inches. This is that famous ' horn ' which figures o on the forehead of the heraldic unicorn, and so long excited the curiosity and conjectures of the older naturalists, until Olaus Wormius made an end of the fabulous ' monocerolocnes ' o by the discovery of the true nature of their subject. 1 1 CLX". Linnasns has embalmed the old idea of this weapon in the binomial Monodon monoceros, under which the Xarwhal is entered in the Systema Naturae. 280 ANATOMY OF VERTEBRATES. The exterior of the long tusk is marked by spiral ridges, which wind from within forward, upward, and to the left. About fourteen 220 inches is implanted in the socket ; it tapers gradually from the base to the apex. The pulp-cavity, as shown in the longitudinal section of the tusk, in fig. 220, is continued nearly to the extreme point, but is of vari- able width : at the base it forms a short and wide cone ; it is then con- tinued forward, as a narrow canal, along the centre of the implanted part of the tooth, beyond which the cavity again expands to a width equalling half the diameter of the tooth ; and finally, but gradually, contracts to a linear fissure near the apex. Thus, the most solid and weighty part of the tooth is that which is implanted in the jaw, and nearest the centre of support, whilst the long projecting part is kept as light as might be compatible with the uses of the tusk as a weapon of attack and defence. The portion of pulp, in which the process of the calcification has been arrested, re- ceives its vessels and nerves by the fissure continued from the basal ex- pansion of the pulp-cavity. In a few instances, both tusks have been seen to project from the jaw. In Delpliinus griseus the dentition of the upper jaw is transitory, as in Hyperoodon, but at least six pairs of teeth rise above the gum and acquire a full development at the forepart of the lower jaw. The crowns of these teeth soon become obtuse, and their duration is limited : aged indi- viduals of this species have been taken with the dentition reduced to Base of skull of male Narwhal, with a section . i .-> i of the Tusk. two teetn in the lower jaw. TEETH OF MONOFHYODONTS. 281 The outward and visible dentition of the great Sperm-whale or Cachalot (Physeter macrocephalus) is confined to the lower jaw. The series consists in each ramus of about twenty-seven teeth. In the young they are conical and pointed ; usage renders them obtuse, whilst progressive growth expands and elongates the base into a fang, which then contracts, and is finally solidified and terminated obtusely. The teeth are separated by intervals as broad as themselves. The mode of implantation is inter- mediate between that of the teeth of the Ichthyosaurus,, and of those of Delphinus. They are lodged in a wide and moderately deep groove, imperfectly divided into sockets, the septa of which reach only about half-way from the bottom of the groove. These sockets are both too wide and too shallow to retain the teeth in- dependently of the soft parts, so that it commonly happens, when the dense semi-ligamentous gum dries upon the bone, and is stripped off in that state, that it brings away with it the whole series of the teeth like a row of wedges half-driven through a o o strip of board. A firmer implantation would seem unnecessary for teeth which have no opponents to strike against, but which enter depressions in the opposite gum when the mouth is closed. That gum, however, conceals a few persistent specimens of the primitive foetal series of teeth ; these are always much smaller and more curved than the functional teeth of the lower jaw, of which a section is given in fig. 239, vol. i. p. 362. In the small snub-nosed Cachalot (Physeter simus) the first tooth of this series is exposed in the front of the upper jaw. 1 The first-formed extremity of the tooth in the young Cachalot is tipped with enamel : when the summit of the crown has been abraded, the tooth consists of a hollow cone of dentine, ib. d, coated by cement, c, and more or less filled up by the ossified pulp, o. Irregular masses of this fourth substance have been found loose in the pulp-cavity of large teeth. The external cement is thickest at the junction of the crown and base, which are not divided by a neck. The permanent or mature dentition of the Beluga (Delphinus leucas, Pall.), though scanty, is more normal than in the Physeter, nine functional teeth being retained on each side of the upper jaw, and eight in each ramus of the lower jaw. They present the form of straight subcompressed obtuse cones. The most formidable dentition is that of the predaceous Grampus (Phoccena orca), whose laniariform teeth are as large in proportion to the length of the jaws as in the crocodile ; they are 1 xcix'. p. 42, pi. 12. 232 ANATOMY OF VERTEBRATES. in number -jf'-ri^O '> a ^ fixed in deep and distinct sockets, sepa- rated by interspaces which admit of the close interlocking of the upper and lower teeth when the mouth is closed ; the longest and largest teeth are at the middle of the series, and they gradually decrease in size as they approach the ends, especially the pos- terior one. In the common Dolphin the number of teeth amount to 190, arranged in equal numbers above and below, and there is a pair of teeth in the premaxillaries which are toothless in the other Cetacea. They have slender, sharp, conical, slightly incurved crowns, and diminish in size to the two extremes of the dental series ; the acute apices are longer preserved than in the foregoing species. The Gangetic Dolphin (Platanista gangetica) differs from the rest of the Delphinida scarcely less in the form of its teeth than in that of the jaws. Both the upper and lower maxillary bones are much elongated and compressed ; the symphysis of the lower jaw is coextensive with the long dental series, and the teeth rise so close to it that those of one side touch the others by their bases, except at the posterior part of the jaw. The lateral series of teeth are similarly approximated in the upper jaw at the median line of union, which line is compelled, by the alternate position of the teeth, to take a wavy course. There are thirty teeth on each side of the upper jaw, and thirty-two on each side of the lower jaw. In the young animal they are all slender, com- pressed, straight, and sharp-pointed, the anterior being longer than the posterior ones, and recurved. Contrary to the rule in ordinary Dolphins, the anterior teeth retain their prehensile structure, while the posterior ones soon have their summits worn down to their broad bases : in the progress of their growth the implanted base is elongated antero-posteriorly, its outer surface augmented by longitudinal folds analogous to those in the teeth of the Sauroid fishes. Sometimes the posterior tooth of Platanista has the base divided into two short fangs, the sole example of such a structure which I have met with in the existing carnivorous Cetacea. In the Dolphins of the South American rivers (Inia) the inner side of the tooth expands into a crushing tubercle. The primitive seat of the development of the tooth-matrix is maintained longer in the Cetacea than in other Mammalia ; a greater portion of the tooth is also developed before the matrix sinks into, or is surrounded by, a bony alveolus ; and, with the exception of the rudimeiital tusks in the Narwhal, is at no period TEETH OF DIPHYODONTS. 283 entirely closed in a bony cell, in which respect the Cetacea offer an interesting analogy to true fishes. 220. Teeth of Diphyodonts. A. Sire?iia.- -Two marks of inferiority in the dental system of the carnivorous Cetacea, which they have in common with many of the order Bruta, viz. a general uniformity of shape in the whole series of teeth, and no succession and displacement by a second or permanent set, disappear when we commence the examination of the dentition of those apodal pachy- derms which were called by Cuvier the Herbivorous Cetacea. In the Dugong (Halicore)^ for example, we find incisors dis- tinguished by their configuration as well as position from the molars, and the incisive tusk is deciduous, displaced vertically, and succeeded by a permanent tusk ; both these characters are shown in fig. 160, vol. ii. p. 281. Of the incisors of the Dugong, only the superior ones project from the gum in the male sex, and neither upper nor lower ones are visible in the female. The supe- rior incisors, ib. z, are two in number in both sexes. In the male they are moderately long, subtriedral, of the same diameter from the base to near the apex, which is obliquely bevelled off to a sharp edge, like the scalpriform teeth of the Rodentia. Only the extremity of this tusk projects from the jaw, at least seven-eighths of its extent being lodged in the socket, the parietes of which are entire. In the female Dugong the growth of the permanent inci- sive tusks of the upper jaw is arrested before they cut the gum, and they remain throughout life concealed in the premaxillary bones ; the tusk in this sex is solid, is about an inch shorter and less bent than that of the male ; it is also irregularly cylindrical, longitudinally indented, and it gradually diminishes to an obtuse rugged point ; the base is suddenly expanded, bent obliquely outwards, and presents a shallow excavation. The deciduous incisors of the upper jaw, z, d, are much smaller than the perma- nent tusks of the female, and are loosely inserted by one extremity in conical sockets immediately anterior to those of the permanent tusks, adhering by their opposite ends to their tegumentary gum, which presents no outward indication of their presence. Not more than twenty-four molar teeth are developed in the Australian Dugong (Halicore Australis), or more than twenty molar teeth in the Malayan Dugong, viz., in the latter, five on each side of both upper and lower jaws, ib. 1-5, but these are never simultaneously in use, the first beino* shed before the last has cut the grim. O o The molar teeth of the Dugong consist of a large body of dentine, a small central part of osteo-dentine, and a thick external investment of cement, c, fig. 242, vol. i. p. 365. In the female 284 ANATOMY OF VERTEBRATES. Dugong the whole of the smaller extremity of the tusk is sur- rounded by a thin coat of true enamel, which is covered by a thinner stratum of cement. In the male's tusk the enamel, though it may originally have capped the extremity, as in the female's, yet, in the body of the tusk, it is laid only upon the anterior convex, and on the lateral surfaces, but not upon the posterior concave side of the tusk, which is thickly coated with cement. This side, accordingly, is worn away obliquely when the tusk comes into use, whilst the enamel maintains a sharp chisel- like edge upon the anterior part of the protruded end of the tusk. The presence of abortive teeth concealed in the sockets of the deflected part of the lower jaw of the Dugong, fig. 160, , z, d (vol. ii.), offers an analogy with the rudimental dentition of the upper jaw in the Cachalot, and of both jaws in the foetal Whales. The arrested growth and concealment of the upper tusks in the female Dugong, and the persistent pulp-cavity and projection of the corresponding tusks in the male, are equally interesting repe- titions of the phenomena manifested on a larger scale in the dental system of the Narwhal. The simple implantation of the molar teeth and their composition are paralleled in the teeth of the Cachalot ; their difference of form, and the more complex shape of the hindmost tooth, ib. b, are repetitions of characters which were present in the dentition of the extinct Zeuglodun. The coexistence of incisive tusks with molar teeth, and the successive displacement of the smaller and more simple anterior ones by the advance of larger and more complex grinders into the field of attrition, already seem to sketch out peculiarities of dentition which become established and attain their maximum in the Pro- boscidian family (Elephants and Mastodons) of the Ungulates. The molars of the American Manatee are thirty-eight in number, ten on each side of the upper jaw, and nine, at least, on each side of the lower jaw ; but they are never simultaneously in place and use. The first in both jaws is small and simple. Beyond the second, the crowns in the upper jaw are square, and support two transverse ridges with tri-tuberculate summits, having also an anterior and posterior basal ridge ; each tooth is implanted by three diverging roots, one on the inner and two on the outer side : they increase in size very gradually, from the foremost to the last. The crowns of the four or five anterior molars of the lower jaw resemble those above, but the rest have a large posterior tubercle ; they are all implanted by two fangs which enlarge as they descend, and bifurcate at the extre- mity ; the crowns are of moderate height, and project only a few TEETH OF DIPHYODONTS. 285 lines above the sockets. The molars consist of a body of dentine, a coronal covering of enamel, and a general investment of cement, very thin upon the crown, and a little thicker upon the fangs. B. Marsupialia. In the Marsupial order, the typical number of the teeth in the molar series is seven on each side of both jaws, the first three of which are ( premolars/ fig. 221, p, i, 2, 3, the last displacing, in some, a calcified predecessor, fig. 296, d 3, and giving the extent of the theoretical deciduous series. Incisors, fig. 221, i, are present in all the species, but are variable in number, in some genera exceeding that of the Mammalian type. Canines, ib. c, are large in the Dasyures, are feebly represented in the Phalan- gers and Petaurists, are absent in the lower jaw of the Potoroos and Koala (fig. 221, vol. ii), and in both jaws of the Kangaroos, fig. 231, and Wombats, fig. 232. The Dasyures and Thylacine offer the carnivorous type of the dental system, but differ from the corresponding group of the placenta! Mammals in having the molars of a more uniform and 221 Dentition of Thylacine. simple structure, and the incisors in greater number : the dental formula of the Dog-headed Opossum, Thylacinus, is- .4.4 1.1 3.3 4.4 1 3~3' C lTI ' P 3~3' m 4~l = 46 ' g ' 22L The canine teeth are long, strong, curved, and pointed ; the points of the lower canines are received in hollows of the pre- maxillary palatal plate when the mouth is closed, and do not project, as in the carnivorous placentals, beyond the margins of the maxillary bones. The premolars, p, present a simple com- pressed conical crown, with a posterior tubercle, which is most developed on the hindmost. The molars, m, in the upper jaw are unequally triangular, the last being much smaller than the rest ; 286 ANATOMY OF VERTEBRATES. 222 The upper true have triangular the exterior part of the crown is raised into one large pointed middle cusp and two smaller cusps ; a small strong obtuse lobe projects from the inner side. The molars of the lower jaw are compressed and tricuspidate ; the middle cusp being the longest, especially in the two last molars, which resemble the feline car- nassials. The dental formula of the genus Dasyurus is i*A. c l.*A. m *A = & fiff 229 O Q * 1 1 y J: O O ' A A ~~~ ? & ^^^' The eight incisors of the upper jaw, fig. 222, are of the same length and simple structure, and are arranged in a regular semi- circle. The premolars, p 2 and 3, answer to the two last in Thylacinus, and have simple crowns, molars, m crowns ; the first presents four sharp cusps ; the second and third each five ; the fourth, which is the smallest, only three. In the lower jaw, the last molar is nearly of equal size with the penultimate one, and is bristled with four cusps, the external one being the longest. The second and third molars have five cusps, three on the inner and two on the outer side ; the first molar has four cusps. The carnivorous character of the above dentition is most strongly marked in the Ursine Dasyure, or Devil of the Tasmanian colonists, the largest existing species of the genus. In some of the smaller species the canines lose their great rela- tive size, and the molars present a surface more cuspidated than sectorial ; there is also an increased number of teeth, and as a consequence of their equable development, they have fewer and shorter interspaces. The subgenus Phasco- gale is characterised by Dentition of Ursine Dasyure. .4.4 LI 3.3 4.4 m - 46, fig. 223. Dentition of Phascogale. 1 3.3' "1.1 ; ^3.3' "4.4 In this formula may be discerned a step in the transition from the Dasyures to the Opossums, not only in the increased number of spurious molars, but also in the shape and proportions of the incisors. The general character of the dentition of these small predatory TEETH OF DIPHYODONTS. 237 Marsupials approximates to the insectivorous type, and leads thereto from the flesh-feeding;; o-enera. o o Myrmecobius is characterised by the following remarkable dental formula: .4.4 1.1 3.3 6.6 Dentition of Myrmecobius. The number of true and false molars, eighteen in both jaws, exceeds that of any other known existing Marsupial. The molars are multicuspid, and both the 224 true and false ones possess two separate fangs. The iru- ferior molars are directed obliquely inward, and the whole dental series describes a slight sigmoid curve, fig. 225. The premolars present the usual compressed trian- gular form, with the apex slightly recurved, and the base more or less obscurely notched before and behind. The canines are very little longer than the false molars. The incisors are minute, slightly compressed, and pointed ; they are separated from each other and the canines by wide intervals. The extinct genus Amphiiherium is founded on fossil remains of lower jaws and teeth discovered in the oolitic slate at Stones- field, in Oxfordshire, and it receives elucidation from the dental characters of the previous genus, but is remarkable for 225 having a still greater number of molar teeth. The dental formula is as follows : ?.? j L ". f 3.3' C j| 6.6' 6.6" There being thus thirty-two teeth in the lower jaw, and probably as many in the upper jaw. The following dental fornmla- .5.5 1.1 i r 3.3' 1.1 3.3 4.4 1 Q 7TTT' " , 7 * characterises a number of Marsupials commonly known in Australia by the name of Bandicoots, fig. 226. The teeth which offer the greatest range of variation in the present genus (Perameles} are the external or posterior teetli Myrme- incisors and the canines : the molars, also, which ori- COMUS. ginally are quinque-cuspidate, have their points worn away, and present a smooth and oblique grinding surface in some species (fig. 222, m, vol. ii.) sooner than in others. 288 ANATOMY OF VERTEBRATES. 226 The Bandicoots which approach nearest to the Myrmecobius in the condition of the incisive and canine teeth, are the Perameles obesula and P. Gunnii. There is u slight interval between the first and second incisor, and the outer or fifth incisor of the upper jaw is separated from the rest by an interspace equal to twice its own breadth, and moreover presents the triangular pointed canine-like crown which characterises all the incisors of Myrmecobius ; but the four anterior incisors are placed close together and have compressed, quad- rate, true incisive crowns. From these incisors the canine is very remote, the interspace being equally divided by the fifth pointed incisor, which the canine very slightly exceeds in size. In Per am. nasuta, fig. 226, the incisors present the same general condition, but the canines are relatively larger. o The dental formula of the genus Didelphys is Dentition of Perameles. 5.5 1.1 3.3 t nr\ , 1.1'^ 3.3' m = 50, fig. 227. 4.4' i;r*- 3.3' 4.4 The Opossums resemble in their dentition the Bandicoots more than the Dasyures ; but they closely re- semble the latter in the tuberculous struc- ture of the molars ; the two middle incisors of the upper jaw are more produced than the others, from which they are also separated by a short interspace. The canines still exhibit a superior development in both jaws adapted for the destruction of living prey, but the molars have a conformation different from that which characterises the true flesh-feeders, and the Opossums consequently subsist on a mixed diet, or prey upon the lower or- ganised animals. The smaller species of Didelphys, which are the most nu- merous, fulfil in South America the office of the insectivorous Shrews of the old continent, The larger Opossums resemble in their habits, as in their dentition, the carnivorous Dasyures, Dentition of Opossum. (Didelpliys) TEETH OF DIPHYODONTS. 289 and prey upon the smaller quadrupeds and birds ; but they have a more omnivorous diet, feeding on reptiles and insects, and even fruits. One large species (Did. cancrivora) prowls about the sea-shore, and lives, as its name implies, on crabs and other crustaceous animals. Another species, the Yapock, frequents the fresh water, and preys almost exclusively on fish : it has the habits of the Otter, but the dentition does not differ from that of ordinary Opossums. In the genus Tarsipes the molars soon begin to fall ; the small canines are also deciduous ; the two procumbent incisors of the lower jaw remain the longest. The inferior incisors are opposed to six minute incisors above, which are succeeded by a small canine and some small molars ; but these are reduced perhaps old, individuals, to a single tooth on each n some side. The Phalangers, being provided with hinder hands and pre- hensile tails, are strictly arboreal animals, and have a close external resemblance to the Opossums. They differ chiefly in their dentition, and in accordance therewith their diet is more decidedly of a vegetable kind. The interspace between the functionally developed incisors and molars in both jaws always contains teeth of small size and little functional importance, and variable not only in their proportions but their number. The constant teeth are the -i^i true molars, and the i^s. incisors. 4 -t 1 - 1 The canines, c, fig. 228, are constant in regard to their presence, but variable in size ; they are always very small in the lower jaw : the functional premolars, p 3, are always in contact with the 298 229 Dentition of Piiaiangista vulpiua. Dentition of Cook's Phalanger. molars and their crowns reach to the same grinding level ; some- times the second premolar is similarly developed in the upper jaw, as in the Phal Cookii, p 2, fig. 229, but it is commonly absent; the first premolar, p i, is a very minute tooth, shaped VOL. III. U 290 ANATOMY OF VERTEBRATES. like a canine : thus, in the upper jaw, between the posterior or functional premolar, p 3, and the incisors, z, we may find three teeth, as in PhaL Cookii, or two teeth as in P/tal. vulpina, the first being the canine, c. In the lower jaw similar varieties occur in these small and unimportant teeth : e. g. there may be between the procumbent incisors and the posterior premolar, either three teeth, as in PhaL Cookii', or two, as in PhaL ursina; or one, as in PhaL vulpina. The most important modification is presented by the little PhaL gliriformis and Petaurus (Acrobates} pi/gm&us, fig. 219, vol. ii., which have only three true molars on each side of each jaw. These minor modifications are unaccompanied by any change of general structure or of habit, whilst those teeth which most influence the diet are constant. The absence of functionless premolars and of lower canines is constant in the Koala (Phascolarctos, fig. 221, vol. ii.). The molars are proportionally larger than in the Phalangers : each is beset with four three-sided cusps, the outer series in the upper teeth being the first to wear down ; those in the lower jaw are nar- rower than in the upper ; there is also the rudiment of a ( cingu- lum.' The premolars are compressed, and terminate in a cutting edge. The small canine is situated close to the premaxillary suture. The dental formula of the Potoroos (Hyi^siprymnus) is 1.1 4.4 .3.3 1.1 * T~ ^ C- ~ 230 The anterior of the upper incisors are longer and more curved than the lateral ones, and their pulps are persistent. The canine is larger than in the Koala ; it is simi- larly situated. In the large Hypsiprymnus ur sinus the canines are relatively smaller than in the other Potoroos, a structure which indicates the transition from the Potoroo to the Kangaroo genus. The single premolar, p 3, has a peculiar trenchant form; its maximum of develop- ment is attained in the arboreal Potoroos of Xew Guinea ; in Hypsiprymnus dorcoceplialus, e.g. its antero-posterior extent nearly equals that of the three succeeding molar teeth. In. all the Potoroos, the trenchant spurious molar is indented, especially on the outer side and in young teeth, by many small vertical grooves. The true molars, m i, 2, 3, 4, have large Dentition of Hypsiprymnus murinus. TEETH OF DIPHYODOXTS. 291 subquadrate crowns ; each presents four three-sided pyramidal cusps ; but the internal angles of the two opposite cusps are con- tinued into each other across the tooth, forming two angular or concave tranverse ridges. In the old animal these cusps and ridges disappear, and the grinding surface is worn quite flat. In the genus Macropus, fig. 231, the normal condition of the permanent teeth may be expressed as follows :- 3.3 0.0 , _ 28 . 1 1.1' "0.0* 1.1' 4.4 The main difference, as compared with Hypsiprymnus, lies in the absence of the upper canines as functional teeth ; but the germs of these teeth are to be found in the young mammary foetus of the Macropus major, and may be detected of very small size, concealed by the gum, in the adults of some small species of Kangaroos, as, e. g., Macropus rufiventer, Ogilby, and Macr. 231 Dentition of Macropus major, one-third nat. size. psilopus, Gould. The crown of the true molars supports two principal transverse ridges, with a broad anterior talon and a narrow hinder one. In most species a spur is continued from the hinder to the fore rido-e, and another from the fore rido;e to the front talon. ^j * ^5 Remains of Kangaroos, larger than any living species, have been discovered in the same caves in Australia which contained the teeth and jaws of the extinct Dasyurus laniarius, and they probably formed the prey of that species and of its contemporary the Thylacine which no longer exists in the continent of Australia. 1 A gigantic extinct herbivorous Australian Marsupial (Dipro- todon\ the bulk of which may be surmised from the length of the skull, which equals three feet, manifests a dentition which makes the nearest approach to that of the Kangaroos ; but the anterior or median pair of upper incisors present the condition of large, curved, scalpriform, ever-growing tusks, 1 cxvin", vol. ii. u 2 292 ANATOMY OF VERTEBRATES. Avhicli work against a similar but straight procumbent pair of incisive tusks below; thus presenting a transitional feature between the Kangaroos and the Rodent form of Marsupial called Wombat (Phascolmnys).' 1 In this genus, the dental system pre- sents the extreme degree of that degradation of the teeth, inter- mediate between the front incisors and true molars, which has been traced from the Opossum to the Kangaroos ; not only have the functionlcss premolars and canines now totally disappeared, but also the posterior incisors of the upper jaw, which we have seen in the Koala and Potoroo to exhibit a feeble degree of develop- ment as compared with the anterior pair ; these, in fact, are alone retained in the dentition of Pliascolomys. The dental formula of the Wombat is thus reduced, both in number and kind, to that of Rodentia, viz.- 2 11 44 * 2 ; c o ; p ii ; m T4 = 24 ' fig> 232t 232 The incisors, ?,* moreover, are ' dentes scalprarii,' but are in- ferior, especially in the lower jaw, in their relative length and cur- vature to those of the placental Glires ; they present a subtriedral figure, and are tra- versed by a shallow groove on their mesial surface. The premolars, /?, 3, present no trace of that compressed structure which cha- racterises them in the Koala and Kangaroos, but have a wide oval transverse section ; those of the upper jaw being traversed, on the inner side, by a longitudinal groove. The true molars, m 1-4, are double the size of the premolars ; the superior ones are also traversed by an internal longitudinal groove ; but this is so deep and wide that it divides the whole tooth into two prismatic portions, with one of the angles directed inward. The inferior molars are in like manner divided into two triedral portions ; but the intervening groove is external, and one of the facets of each prism is turned inward. All the grinders are curved, and describe about a quarter of a circle. In the upper jaw the concavity of the curve is directed outward ; in the 1 CLXXX, p. 431. Dentition, Phascolomys fuscus, i nat. size. TEETH OF DIPHYODONTS. 293 lower jaw, inward. The false and true molars, like the incisors, have persistent pulps, and are, consequently, devoid of true fangs, in which respect the Wombat differs from all other Marsupials, and resembles the extinct Toxodon, the dentigerous Bruta, and herbivorous Rodentia. A retrospect of the modifications of marsupial dentition shows them to be divisible into two classes : one ' polyprotodont,' or cha- racterised by several pairs of mandibular incisors ; the other ( di- protodont,' or by a single pair : these are large, more or less procumbent, and ever-growing ; the incisors of the first group are small, and of the usual limited growth. The polyprotodont type prevails in the American genera: the diprotodont obtains in the majority of the Australasian marsupials, and is associated usually with vegetarian or promiscuous diet. There did exist, however, coeval with Diprotodon, Nototherium, &c., in a ter- tiary age in Australia, a carnivorous marsupial equalling the Lion in size, with the di- _/ "* i protodont type of dentition adaptively modified for prey- ing on the huger contem- poraneous Herbivora. The pair of incisors in the lower jaw, fig. 233, i, and their homotypes above, i i, were ( canines ' in size and shape : a single tooth of the , . ^ i f Dentition of Tliylacoleo. molar series on each side ot both jaws, ib. p 4, was concomitantly modified to act as a ( sec- torial ' or flesh-cutting tooth ; the crown beino; narrow or O * o 6 compressed,' long antero-posteriorly, with the sides marked by vertical folds or grooves, and converging to a rather oblique cutting edge, that of the upper blade playing on the outside of the lower one. These f sectorials ' were larger than in the Lion or Tio-er, and were even more ( carnassial ' as wanting the s tubercle,' O 3 O ' and consisting wholly of the ' blade.' Behind the upper sectorial is one small tubercular, m i, of the relative proportion of that in Felis : the lower sectorial is followed by two small teeth with subtuberculate crowns, m ], m 2. The teeth between the carnas- sials and laniary incisors are too small for definite use. So far as present fossils show, the dentition of Tliylacoleo was :- .3.3 1.1 2.2 1.1 'n ;c ao ; ^ ;m ^2 =24 ' The chief business of the teeth was delegated to the tusks and 294 ANATOMY OF VERTEBRATES. 234 Dentition of lower jaw, Plagiaulax. carnassials ; development was concentrated on these at the cost of the rest of the normal or typical dental s'eries. The foremost teeth seized, pierced, lacerated or killed, the carnassials divided the nutritive fibres of the prey. Thylacoleo exemplifies the simplest and most effective dental machinery for predatory life known in the Mammalian class. It is the extreme modification, to this end, of the diprotodont type of Marsupialia. The skull exhibits all the concomitant carnivo- rous modifications, in a like extreme degree. 1 It is interesting to note that, just as the exceptional modifica- tion of the polyprotodont type, in the modern Myrmecobius, was manifested by Amphitlierium in Oolitic times, so likewise was the zoophagous diprotodont modifica- tion ; but on a smaller scale than in Thylacoleo. The lower incisor in Plagiaulax, fig. 234, i, was a large, upcurved, pointed tusk : the carnassial, p. 4, was of great fore- and-aft length, coupled with nar- rowness, and an oblique cutting edge, rendered sub-serrate by the better-marked and more oblique lateral grooves, than in Tliyla- coleo. Anterior to the carnassial, p, 4, there are two or three similar and smaller sectorial premolars, in Plagiaulax, more of the general diphyodont type being retained in the older zoopha- gous diprotodont. Behind the carnassial are two small tubercu- late molars, m 1, m 2, as in Thylacoleo. Some Palaeontologists, neg- lecting Cuvier's guide-post of the true molar as the light-giving tooth, have been led astray in regard to the affinities of Plagi- aulax, referring it to the ( poephagous Potoroos and Kangaroos,' which combine with a single trenchant and grooved premolar, four large and massive grinders, of quadricuspid or transversely ridged structure. C. Rodentia. In different orders of the placental as in the marsupial diphyodonts there are instances in which the ordinary number of incisors is diminished, and their growing power trans- ferred to a single pair of tusks projecting from the forepart of the upper or the lower jaw, or of both. The Dinotheres, Toxodons, Mastodons, and Elephants, among the Ungulata, the Dugong in the Sirenia, the Aye-aye in the Quadrumana, are instances of this modification, which reaches its extreme in the latter mammal and the elephants. In numerous Lissencephala a single pair 1 cxix". TEETH OF DIPHYODOXTS. 295 of large curved ever-growing incisors, in each jaw, is combined with so many peculiarities of structure, as to have led to their association into one order l called by Linnaeus Glires and by Cuvier ( Rongeurs ' or ( Eroders,' from the gnawing power and habit resulting from such dental modification. The incisors, fig. 235, i, 'i, are separated by a wide interval from the molars : the upper pair, ib. z, describe a larger segment of a smaller circle, the lower ones, ib. ?, a smaller segment of a larger circle ; these are the longest incisors, and usually have 235 Dentition of the Capybara. their alveoli extended below, or on the inner side of, those of the molars, to the back part of the lower jaw, fig. 129 : but in the Hare they reach only midway toward the angle. As in all teeth of unlimited growth, the implanted part of the incisors, besides its length, retains the form and size of the exposed part or crown, to the widely open base, which contains a long conical persistent dentinal pulp, ib. a, and is surrounded by the capsule in a pro- gressive state of ossification, as it approaches the crown; an enamel-pulp is attached to the inner side of that part of the cap- sule which covers the convex surface of the curved incisor. The calcification of the dentinal pulp, the deposition of the earthy salts in the cells of the enamel-pulp, and the ossification of the capsule, proceed contemporaneously; fresh materials being added to the base of the vascular matrix as its several constituents are progressively converted into the dental tissues in the more advanced part of the socket. The tooth, thence projecting, consists of a body of compact dentine, sometimes with a few short medullary canals continued into it from the persistent pulp-cavity, with a plate of enamel laid upon its anterior surface, and a general investment of cement, w T hich is very thin upon the enamel, 1 Vol. ii. p. 276. 296 ANATOMY OF VERTEBRATES. but less thin, in some Rodents, upon the posterior and lateral parts of the incisor. The substances of the incisor diminish in hardness from the front to the back part of the tooth, not only in so far as the enamel is harder than the dentine, but because the enamel consists of two layers, of which the anterior and external is denser than the posterior layer, and the posterior half of the dentine is rendered by a modified number and arrangement of the dentinal tubes less dense than the anterior half. The abrasion resulting from the reciprocal action of the upper and lower incisors produces, accordingly, an oblique surface, sloping from a sharp anterior margin formed by the dense enamel, like that which slopes from the sharp edge formed by the plate of hard steel laid on the back of a chisel ; whence the name ' scalpri- form,' ( dentes scalprarii,' given to the incisors of the Rodentia. In Leporidce the enamel is traceable to the back of the incisors : with this exception, the varieties to which these incisors are sub- ject in the different Rodents are limited to their proportional size, and to the colour and sculpturing of the anterior surface. Thus in the Guinea-pig, Jerboa, and Squirrel, the breadth of the incisors is not half so great as that of the molars: whilst in the Coypu they are as broad as the molars, and in the Cape Mole-rats (Bathyergus and Orycteromys} are even broader. In the Coypu, Beaver, Agouti, and some other Rodents, the enamelled surface of the incisors is of a bright orange or reddish-brown colour. In some genera of Rodents, as Orycteromys, Otomys, Merioncs, Ht/drochoerus, Lepus, and Layomys, the anterior surface is indented by a deep longitu- dinal groove. This character seems not to influence the food or habits of the species : it is present in one genus and absent in another of the same natural family. In most Rodents the anterior enamelled surface of the scalpriform teeth is smooth and uniform. The molar teeth are always few in number, obliquely implanted and obliquely abraded, the series on each side converging ante- riorly in both jaws ; but they present a striking contrast to the incisors in the range of their varieties, which are so numerous that they typify almost all the modifications of form and structure which are met with in the molar teeth of the omnivorous and herbivorous genera of other orders of mammalia. In some Rodents e.g. Cavies, the molar teeth, fig. 236, /?, m, are rootless ; others e.g. the Agouti, have short roots, tardily developed like the molars of the Horse and Elephant ; others, again e.g. the Rat and the Porcupine, soon acquire roots of the ordinary pro- portional length. TEETH OF DIPHYODONTS. 297 The differences in the mode of implantation of the molar teeth relate to the differences of diet. The Rodents, which subsist on mixed food, and which betray a tendency to carnivorous habits, as, e.g., the true Rats, or which subsist on the softer and more nutri- tious vegetable substances, such as the oily kernels of nuts, suffer 236 Cranium and upper teeth of the Patagonian Cavy (Dolichotis). less rapid abrasion of the molar teeth : a minor depth of the crown is therefore needed to perform the office of mastication during the brief period of existence allotted to these active little Mammals : and as the economy of nature is manifested in the smallest parti- culars as well as in her grandest operations, 110 more dental sub- stance is developed after the crown is formed, than is requisite for the firm fixation of the tooth in the jaw. Rodents that exclusively subsist on vegetable substances, espe- cially the coarser and less nutritious kinds, as herbage, foliage, the bark and wood of trees, wear away more rapidly the grinding surface of the molar teeth ; the crowns are therefore larger, and their growth continues by reproduction of the formative matrix at their base in proportion as its calcified constituents, forming the exposed working part of the tooth, are worn away. So long as this reproductive force is active, the molar tooth is implanted, like the incisor, by a long undivided continuation of the crown. The rootless and perpetually growing molars are always more or less curved, fig. 236, p, m ; they derive from this form the same advantage as the incisors, in the relief of the delicate tissues of the active vascular matrix from the effects of the pressure which would otherwise have been transmitted more directly from the grinding surface to the growing base. The complexity of the structure of the crown of the molar teeth, and the quantity of enamel and cement interblended with 298 ANATOMY OF VERTEBRATES. the dentine, are greatest in the rootless molars of the strictly herbivorous Rodents. The crowns of the rooted molars of the omnivorous rats and mice are at first tuberctilate. When the summits of the tubercles are worn off the inequality of the orindino- surface is for a time maintained by the deeper transverse o O * folds of enamel, the margins of which are separated by alternate valleys of dentine and cement ; but these folds, sinking only to a slight depth, are in time obliterated, and the grinding surface is reduced to a smooth field of dentine, with a simple border of enamel. Examples of various forms assumed by the inflected folds of enamel in the molars of the Rodentia are given in the works of the Cuviers and other naturalists. 1 These folds have a general tendency to a transverse direction across the crown of the tooth (vol. ii. fig. 236, p. 370) : the joint of the lower jaw almost restricts it to horizontal movements to and fro, in the direction of the axis of the head, during the act of mastication. When the folds of enamel dip in vertically from the summit to a greater or less depth into the substance of the crown of the tooth, as in those molars which have roots, the configuration of the grinding sur- face varies with the degree of abrasion ; but in the rootless molars, where the folds of enamel extend inward from the entire length of the sides of the tooth, the characteristic con- figuration of the grinding surface is maintained without varia- tion, as in the Guinea-pig, the Capybara, and the Patagonian Cavy. The whole exterior of the molar teeth of the Rodentia is covered by cement, and the external interspaces of the enamel-folds are filled with the same substance. In the Chinchillidce and the Capybara, where the folds of enamel extend quite across the body of the tooth, and insulate as many plates of dentine, these detached portions are held together by the cement. Such folds of enamel are usually parallel, as in the large posterior lower molar of the Capybara, which, in shape and structure, offers a very close and interesting resemblance to the molars of the Asiatic Elephant. The modification observed in the Voles (Arvicola) calls to mind the molars of the African Elephant. The partial folds and islands of enamel in the molars of the Porcupine and Agouti foreshow the structure of the teeth of the Ehinoceros. The opposite lateral inflections of enamel in the molars of the Gerbille and Cape Mole-rat, represent the structure of the molars of the Hippopotamus. The double crescentic folds in the Jerboa sketch 1 cxx". and cxxi". TEETH OF DIPHYODOXTS. 299 out, as it were, the characteristic structure of the molars of the Anoplothere and Ruminants, &c. The transverse section of the molar of the Water-vole, fig. 237, shows that modification of the grinding surface in which the folds 237 Structure of the molar of the Water-vole (Arvicola amphibia), magnified. of enamel, e, extend like promontories, some outward, the others inward, into the substance of the crown ; a like section of the Beaver's molar exhibits islands with a promontory of enamel. The transverse section of the crown of the molar of Lac/ostomus displays not fewer than five islands of enamel, which hard sub- stance is so thick that it enters more abundantly into the compo- sition of the tooth than the dentine itself. The pulp, after the formation of a certain thickness of tubular dentine, becomes converted into osteo-dentine in both the rooted and rootless molars of the Rodents. This fourth substance is exhibited at o, fig. 237, which shows the four different dental tissues, viz. cement, c, enamel, e, dentine, d, and osteo-dentine, o, entering in more equal proportions into the formation of the crown than in other Mam- malian teeth. AVhen the crown is worn by mastication down to the place of the section figured, the four substances appear in the same proportions on the grinding surface, contributing to its effi- ciency as a triturating organ by the inequalities consequent on their various degrees of density and resistance to the abrading forces. The molars are not numerous in any Rodent ; the Hare and Rabbit (Lepus) have J-:f, i.e. six molars on each side of the upper jaw, fig. 238, and five on each side of the lower jaw, vol. ii. fig. 233. The Pika (Lagomys) has J-:|-. The Squirrels have -f :f. The families of the Dormice, the Porcupines, the Spring-rats (Echimyid(E\ the Octodonts, the Chinchillas, and the Cavies, figs. 235, 236, have f :-f molars. In the great family of Rats (Murida SCO ANATOMY OF VERTEBRATES. the normal number of molars is :; but the Australian Water- rat (Hydromys^ has but -|:-| molars, making, with the incisors, twelve teeth, which is the smallest number in the Rodent order. The greatest number of teeth in the present order is twenty-eight, which is exemplified in the Hare and Rabbit; but forty teeth are developed in these species, ten molars and two incisors being deciduous. The first or anterior of the molar series, whether the number be 2-2, 3-3, or 4-4, is a premolar ; it has displaced a deciduous predecessor in the vertical direction. When the series extends to 5-5 or 6-6, the additions are to the fore part, and are pre- molars. This it is which constitutes the essential distinction between the dentition of the marsupial and the placental Rodent ; the latter, like the placental Carnivora, Quadrumana, and Ungu- late*, having never more than three true molars. Thus the Rodents which have the molar formula of -*:-, shed the first tooth in each series, and this is succeeded by a permanent premolar, which comes into place later than the true molars later at least than the first and second, even when the deciduous molar is shed before birth, as was observed by Cuvier in the Guinea-pig. In the Hare and Rabbit, three anterior teeth in the upper jaw, fig 238, p, succeed and displace three deciduous predecessors, ib. d, coming into place after the first and second true molars, ib. m, are in use, and con- temporaneously with the last molar. It does not appear that the scalpriform incisors, ib. z, are preceded by milk teeth, or, like the premolars of the Guinea-pig, by ute- rine teeth ; but the second incisor, ib. z, 2, is so preceded e.g. by the tooth marked d } i, 2, at which period of dentition six incisors are present in the upper jaw. This condition is interesting both as a transitory mani- festation of the normal number of incisive teeth in the mammalian series, and as it elucidates the disputed nature cf the great anterior scalpriform teeth of the Rodentia. It has been contended that they are canines, because those of the upper jaw extended their fang backward into the maxillary bone, which lodged part of their hollow base and matrix. But the scalpriform teeth are confined exclusively to the premaxillary bones at the beginning of their formation, and the smaller incisors which are developed behind them, in our anomalous native Rodents, the Hare and Upper deciduous and permanent teeth of the Hare. TEETH OF DIOPHYODONTS. 301 Rabbit, retain their usual relations with the premaxillaries, thus proving, a fortiori, that the tooth which projects anterior to them must also be an incisor. The law of the unlimited growth of the scalpriforai incisors is unconditional ; and constant exercise and abrasion are required to maintain the normal and serviceable form and proportions of these teeth. When, by accident, an opposing incisor is lost, or when, by the distorted union of a broken jaw, the lower incisors no longer meet the upper ones, as sometimes happens to a wounded hare, the incisors continue to grow until they project like the tusks of the elephant, and their extremities, in the poor animal's painful attempts to acquire food, also become pointed like tusks. Following the curve prescribed to their growth by the form of their socket, their points often return against some part of the head, are pressed through the skin, then cause absorption of the jaw-bone, and again enter the mouth, rendering mastication impracticable and causing death by starvation. I have seen a lower jaw of a beaver, in which the scalpriform incisor has, by unchecked growth, described a complete circle. The point had pierced the masseter Forepart of upper jaw of a nai.iMt, \\-mi , i - ,1 T i n ,1 incisors of abnormal growth. muscle, and entered the oack ot the mouth, passing between the condyloid and coronoid processes of the lower jaw, descending to the back part of the molar teeth, in the advance of the part of its own alveolus, which contains its hollow root. The upper jaw of a Rabbit, with an analogous ab- normal growth of the scalpriform and accessory incisors, is shown in fig. 239. D. Insectivora.- -The dental system in this order is remarkable for the many varieties and even anomalies which it presents- almost the only characteristic predicable of it being the presence of sharp points or cusps upon the crowns of the molar teeth, which are always broader in the upper than in the lower jaw. The teeth that intervene between these and the incisors are most variable in form and size, but are never absent ; the incisors differ in number, size, and shape, in different species, the anterior ones approximating in some species to the character of the scalpri- form teeth of the Rodents. They may be wholly absent in the upper jaw, fig. 242, A. The Chrysochlore, or iridescent Mole of the Cape, makes the nearest approach, by the number of its molar teeth, fig. 240, to 302 ANATOMY OF VERTEBRATES. 240 that remarkable condition which a solitary genus (Myrmecobius) of existing Marsupials also presents, and which was more abun- dantly manifested in the extinct Amphitheria and Spalacotheria of the Oo- litic period. At least f:f true molars may be as- signed to the Chryso- chlore according to their form the only charac- ) ter, in the absence of the known order of their vertical displacement and succession, by which the true and false molars can at present be defined in this species. In the upper jaw, ib. 1, the an- terior large laniariform tooth, and the two suc- ceeding small teeth, are incisors, by virtue of their position in the pre- maxillary bones ; the next small tooth, with a simple compressed tricuspid crown, may be regarded either as a canine or a premolar. The crowns of the true molars are thin plates, narrowed from be- fore backward, with two notches on the working edge, and a longi- tudinal groove along the outer and thicker margin. Another anomaly, more remarkable than that of the shape of the true molars, is their separation from each other by vacant intervals, as in many Reptiles. The crowns of the five lower true molars, ib. 2, 2... 6, are com- pressed antero-posteriorly, but are of unusual length, and have the thicker maroin turned inward ; the summit of the outer O ' border is pointed and most prominent ; the inner division is sub- divided into two points. The anterior incisor is small and pro- cumbent ; the second has a larger laniariform crown ; the third is small, and resembles the two premolars which intervene be- tween this and the first large tricuspid molar. The lower molars are separated by wider intervals than those above ; the crowns of the opposing series enter reciprocally the interspaces, and inter- lock ; in mastication, the anterior margin of the lower tooth works upon the posterior margin of the opposite upper tooth. Dentition of Chrysochlore, magn. 1. Upper jaw, 6 side view, a grinding surface. 2. Lower jaw, a grinding surface, & side view. TEETH OF DIPHYODONTS. 303 The views of the nature of these teeth, as given in the foregoing description, are expressed by the following formula :- .3.3 1.1 6.6 m - - = 40. 241 '3.3 5 ^2.2 5 "5.5 The small insectivorous mammal, called Spalacotherium , which has left its fossil remains in the upper Oolite of Purbeck, had ten molar teeth on each side of the lower jaw, of which six at least presented a tricuspid crown with proportions very similar to those of the Chrysochlore. In the Shrew-moles of America (Scalops) the dentition makes an important step towards the normal mammalian condition, by the restriction of the characters of the true molar teeth to the three posterior ones in each lateral series. Between these and the large scalpriform incisor, in the upper jaw, there are six teeth, the first two of which must also be regarded, by the analogy of the Chrysochlore, as incisors ; the next tooth might pass for a canine ; and the remaining three for premolars : of these the last is the largest, and has a triedral pointed crown. The true molars have large crowns, each with six cusps, four on the outer, and two on the inner part of the grinding surface. In the lower jaw the first incisor is small and procumbent, and the second large and lani- ariform ; the third is absent, and a vacant space separates the incisors from the three premolars, and the crown of each true molar consists of two parallel three-sided prisms, each terminated by three cusps, and having one of the angles turned out- ward, and one of the faces inward. The dental formula of this genus, according to the above description, is . 3.3 ^ 1.1 3.3 3.3 n QJO 2.2' 1.1 3.3 7-1 _ ' P 3.3' 3.3 = 36. Dentition of Mole (Talpa). The dentition of the common Mole (Talpa europcea), fig. 241, includes eleven teeth on each side of both upper and lower 304 ANATOMY OF VERTEBRATES. j:iws. The first three, i, in the upper jaw are very small, with simple incisive crowns, and are each implanted by a long and slender i'ung in the premaxillary, 22 : these teeth are incisors. The next tooth, c, by the size and shape of the crown, represents a canine, but it is implanted by two fangs, like the succeeding premolar teeth. Three of these teeth, /; 1,2, 3, are of small size, with compressed conical crowns ; the fourth premolar, p 4, has a larger three-sided conical crown, supported by three fangs : the crowns of the true molars, m i, 2, 3, are multicuspid ; the middle one the largest, with five points, and usually supported by four fangs, the hindmost the smallest, with a tricuspid crown and three fangs. In the lower jaw the first four teeth on each side are small, simple, and single-fanged, like the three incisors above, but the outer- most, c, is the largest ; the fifth tooth has a large laniarifprm crown, supported by two fangs, being very similar to, but shorter than, the two-fanged canine above. As it passes behind that tooth when the mouth is shut, we must regard it as a premolar, pi: it is the first and largest of the series of four premolars, each' of which has a small posterior talon at the base of the com- pressed conical crown. The three true molars, m i, 2, 3, are each implanted by two fangs, and have quinque-cuspid crowns, the middle molar being the largest. According to this homology, the dental formula of the genus Talpa is .3.3 1.1 4.4 3.3 The teeth are equal in number, and alike in both jaws ; the true molars are reduced to the normal quantity in the placental series, and the entire dentition is the least anomalous of any which is manifested in the family TalpidcB. The transition from the Moles to the Shrews seems to be made by the Water-moles (My gale} and the Solenodon. The latter insectivore combines the form of a gigantic Shrew, with a denti- tion resembling that of the Chrysochlore. Each premaxillary bone contains three incisors, the first large, canine-shaped, grooved anteriorly, with the point inclined backward ; the other two incisors small, with simple conical crowns ; these are succeeded by seven teeth, the two anterior having three-sided conical crowns, the other five bearing, in addition, an external tuber- culate basal ridge. In the lower jaw. the anterior incisor is^very small, and the second large and laniariform, as in Scalops, but it is remarkable for a deep longitudinal excavation upon its inner side ; the third lower incisor is small and simple. Of the seven TEETH OF DIPHYODONTS. 305 succeeding teeth, the four last have multicuspid crowns like true molars. Potamoc/ale l has- . 3.3 0.0 3.3 3.3 070 3^ 3T3 = 36 ' In this large otter-like piscivorous shrew the anterior tooth of the premolar series, in the above formula, may be homologous with the canine in fig. 242 ; the double fang of the upper one would not bar such determination. The posterior incisors and the premolars have triangular trenchant crowns like the teeth of some sharks : the anterior upper, and the second lower, incisors are large and prehensile, as in Solenodon. The typical Shrews always manifest their rodent analogy by the great preponderance of the anterior pair of incisors in both upper and lower jaws (vol. ii. p. 277, fig. 155 3 ). In the lower jaw the great incisor, ib. 2, i, is uniformly succeeded by two small, p 3, 4, and three lar;e, m i, 2, 3, multicuspid molars; but in the upper jaw the number of small premolars varies. The last true molar is commonly of small size. The subgenera of Shrews are chiefly based upon the form of the large incisors and the numerical variations of the dentition of the upper jaw. In the common Shrew (Sorex araneus, Linn.) there are three true molars and four small teeth between these and the anterior incisor ; this tooth, ib. 1 , i, has a pointed tubercle at the back of the base of the crown. The long procumbent incisor of the lower jaw has the trenchant supe- rior margin entire. In the Sorex (Amphisorex) tetragonurus, the upper edge of the lower incisor is notched ; the large upper incisor appears bifurcate from the great development of the posterior talon ; five small teeth, progressively decreasing in size, intervene between the upper large incisor and the true molars. In the Sorex (Hydrosorex) Hermanni, the trenchant edge of the lower procumbent incisor is entire ; there are four small teeth between the large anterior incisor and the true molars in the upper jaw, as in the great Sorex indicus\ but the three first are sub equal, and the fourth very minute ; there is a fourth small true molar above. The enamelled tips of the teeth of the species of Amphisorex and Hydrosorex are stained of a bright brown colour ; the teeth of Sorex proper, as the common Shrew r ( S. araneus), are not so stained. 4 In the progress of the formation of the large notched incisors, the summits of the tubercles are first formed as detached points, 1 Du Chaillu, xm'', and CLXVI", p. 353. 2 CLXV", p. 6. 3 In this figure the tooth marked p 1, being at the suture of the premaxillary with the maxillary, should be the canine, c 1. 4 CLXVII", p. 6. VOL. III. X 306 ANATOMY OF VERTEBRATES. supported upon the common pulp, and do not become united until the centripetal calcification has converted this into a common dentinal base. Some anatomists have regarded the large incisor so formed as an aggregate of two or three teeth ; but in Sorex proper and Ilydrosorex, the calcification of the lower incisor spreads from a single point, and the interpretation of the notched incisor of the Amphisorex, as the representative of these incisors, might, by parity of reasoning, be applied to the human incisor teeth, the dentated margins of which are likewise originally three or four separate tubercles. The determination of the small teeth between the large an- terior incisors and the multicuspid molars depends upon the extent of the early anchylosed premaxillaries ; the incisors being defined by their implantation in those bones, the succeeding small and simple-crowned molars must be regarded as premolars, not any of them having the development or office of a canine tooth ; their homo types in the lower jaw are implanted by two roots. The thickness of the enamel, in proportion to the body of dentine, is unusually great in these small insectivores, and the sharp points of the teeth long retain their fitness for the office of cracking and crushing the hard or tough teguments of insects. The enamel-pulp of the lower incisors is so large as to over- lap, in the young Shrew, the growing margin of the socket, so as to encase with enamel not only the crown of the tooth, but also the contiguous part of the jawbone : the roots of these teeth 042 also become anchylosed to the jawbone, a reptilian cha- racter offered by the Soricidce alone in the Mammalian class. In a large long-legged and long-snouted African Shrew (Rhynchocyon, Peters ') the lower incisors are bilobed ; the upper ones absent, giving the following dental for- mula, fig. 242 :- .0.0 1.1 3.3 3.3 1 3^3 5 T7l ; P 3.3 ; m 373 = The premaxillaries terminate Dentition of Rhynchocyon. LXXXIV'. 1 -i i in a trenchant edentulous border, A, as in the true ruminant : to the hard gum covering it are ~ ~ opposed the crowns of the six lower incisors, ib. B, i ; a canine, c, with a similar-sized but simple crown, seems part of the semi-cir- 1 LXXXIV', p. 10G. TEETH OF DIPHYODONTS. 307 cular incisive series, as in ruminants, and is separated by a slight interval from the premolar, 2. The canine above, A, c, has a long compressed pointed crown, with a sharp hind border : its root is deeply implanted and divided into two fangs : it descends outside the lower teeth and their alveoli, reminding one of the canines in the small Musk-deer. The upper premolars, A, p, 2, 3, 4, have compressed pointed crowns increasing in size as they approach the molars : the hind border of the second has one notch, that of the third two notches, and a low sub-bilobed inner portion. The molars decrease in size to the third : the first and second above have two outer cusps more produced than the two inner ones : the third molar has the hind pair blended into one cusp. The first lower premolar has a longer but thinner crown than the last. The first and second lower molars are 4-cuspid ; the third, 3-cuspid ; and the first has an anterior talon. Macroscelides and Pctrodromus, also South African Insec- tivora with long hind-limbs and a long snout, have similar 4-cuspid molar teeth, the last molar the smallest and with the outer and inner cusps of the hind pair blended into one. The last premolar above has a low beginning of the inner cusps, which are the lowest in the true molars. In the lower jaw of Macroscelides fuscus the type series is preserved, viz. : i 3, c i , p 4, m 3 ; but p \ is undeve- loped above; and p \ is wanting, both above and below, in Pe- trodromus, as in Rhynchocyon. Bdeof/ale crassicauda (Pe- ters), with the following for- mula : 24.3 o o 11 . O .O I.I -/ 3.3' 1.1 ' 3.3 3.3 m - - = 40, 3.3' "3.3 is remarkable for the large pro- portional size of the upper outer incisor, which almost equals the canine. In the dentition of the Tu- paias (Glisorex, fig. 243) we trace characters intermediate between those of Shrews and Hedgehogs. The dental formula of Glisorex tana is- .2.2 1.1 3.3 3.3 P .TO 5 o-o = 36 - Dentition of Tupain. 1. Upper jaw, b side view, working surface 2. Lower jaw, a working surface, b side view. 2.2' '1.1' 3.3 x 2 3.3 -508 ANATOMY OF VERTEBRATES. The upper incisors are small, simple, and wide apart in the upper jaw, 1 ; the anterior incisor in the lower jaw, 2, is long and procumbent, but relatively smaller than in the Shrews ; the canines are small in both jaws ; the premolars, 2, 3, 4, increase in size and complexity as they approach the true molars, i, 2, 3. In Gymnura each premaxillary bone contains three teeth ; the next has the form and size of a canine in both upper and lower jaws, but has two roots in the upper jaw ; this is followed by four premolars, the last of which, in the upper jaw, is large and quad- ricuspid : the first and second of the true molars have square multicuspid crowns; the last molar is smaller and triangular. In the lower jaw the fourth premolar has a compressed tricuspid crown. The dental formula of Gymnura is typical, viz. : .3.3 1.1 4.4 .3 The dentition of our common Hedgehog (Erinaceus europceus) shows greater inequality in the upper and lower jaws, the formula beino; O 3.3 1.1 l ; c - 3.3' 0.( 3.3 2.2 ; m H = 36 ' fig '' 244 ' The first incisor in both upper and lower jaws is larger and 244 2 longer than the rest, and is very deeply implanted in the jaw ; the tooth which follows the incisors is small in both jaws, but especially so in the lower ; it may be called a canine with two roots in the upper jaw, p i. The last premolar is the largest in both jaws ; above it has a quadri- cuspid crown with three fangs ; below, a subcom- pressed tricuspid crown with two fangs. The true molars decrease in size from the first to the third in both jaws, the first and second have sub- quadrate four-pointed crowns above ; below, they are narrower, and the anterior and inner angle is produced into a fifth cusp. Dentition of Hedgehog. 1. Lower jaw, b side view, a working surface. 2. Upper jaw, a working surface, b side view. TEETH OF DIPHYOBONTS. 09 The true molars of the tropical Hedgehogs, forming the sub- genera Echinops and Ericulus, are more simple, and approach the form of those in the Chrysochlore, being compressed from before backward, with two outer cusps and one inner cusp in the upper jaw, and with one outer and two inner cusps in the lower jaw. The number of incisors is -f:-| in both subgenera, which are followed by |-:|- small and simple premolars ; but Ericulus has J-:J- compressjed tricuspid molars, and Echinops only -:J. The large Tenrecs or tailless Hedgehogs of Madagascar, com- bine the simple molars of Ericulus with the most formidably developed canines which are to be met with in the whole order Insectivora. The incisors are two in number in the upper jaw, but three in the lower jaw; very small and sub-equal in both; the canines are long and large, compressed, trenchant, sharp- pointed, recurved, and single-fanged, thus presenting all the typical characters of those teeth in the Camivora. They are separated in both jaws by a wide space from the premolars ; the first above is compressed, unicuspid with a hinder talon-, and two-fanged ; the second has a larger prismatic tricuspid crown and three fangs ; of the four posterior teeth, which by their aiitero- posterior compression may be regarded as true molars, the first three have tricuspid crowns as in the Echinops, and have three fangs ; the fourth is smaller, is tricuspid, and has two fangs ; all the lower molars have two fangs. The teeth of Insectivora consist of a basis of hard dentine, with a thick coronal investment of enamel, and an outer covering of cement, very recognisable in the interspaces of the coronal cusps in microscopic sections of the molars of the larger species, as the Tenrecs and Macroscelids, and always thick when it closes the extremity of the fangs. Here the cement is commonly more highly organised, is traversed by medullary canals, generally presenting concentric walls ; it thus assumes the character of true bone, and, in the SoricidcB, is frequently continued into the sub- stance of the jaw itself. The small proportion of dentine, in comparison with the thick layer of enamel, has been already alluded to in the Shrews, yet the dentinal tubuli are at their commencement very little inferior in diameter to those of the human incisors; the trunks are very short, and are resolved into radiated penicilli of undulating branches, which quickly subdivide, interlace and anastomose together near the boundary line between the dentine and enamel. In most of the Insectivora, the secondary branches of the den- tinal tubes are unusually conspicuous, especially in the dentine 310 ANATOMY OF VERTEBRATES. forming the fangs. The dentinal compartments (vol. i. fig. 237) are rarely well defined ; in the large canines of the Centetes they are subhexagonal. o The deciduous teeth of the Moles and Shrews are uterine, i.e., are developed and disappear before birth. They are extremely small, and are all of the most simple form. In the fetal Sorex araneus calcification of the papillary exposed pulps of the teeth, which are succeeded by the first and second premolars, proceeds to a very slight extent, and these microscopic rudiments appear to be absorbed rather than shed. The deciduous incisors arc further advanced before their displacement, and present the form of equal-sized dentinal spicula, tipped with enamel, attached by the opposite end to the gum, and not exceeding -j-Jth of an inch in length ; the number of the uterine series of teeth is 4:4. o o o Iii the volant Insectivora, or Bats, the canines are always present in both jaws, of the normal form, and with slightly variable proportions. The molar series never exceeds -|:f , and is divisible into premolars and true molars ; the latter are bristled with sharp points in the great bulk of the Cheiroptera. The inci- sors are the most variable teeth ; they may be entirely wanting, or be present in the numbers of '.' l w ~'^ ; they are always very small, and, in the upper jaw, commonly unequal, and separated by a wide median vacancy. In the genus Chilonycteris, the mid- incisors above and the outer ones below have the crown notched ; the mid-incisors below have two notches, producing three lobes on the cutting border. Taking the common simple-nosed Bat ( Vespertilio murinus) as a type of this Insectivorous group, we find its dental formula to be 245 .2.2 1.1 3.3 3.3 -= 38. In the leaf-nosed Bats (Phyllostoma, fig. 245) the incisors are f:|, the mid pair above being large and laniariform ; the canines are well-developed in both jaws. The second premo- lar above has a large, tried ral, pointed crown. The first and second molars have two large external, and three small internal cusps. The dentition of the blood-suckino; Bats deviates, as might be t_? y ^^ Dentition of leaf-nosed Bat (riujllostoma). TEETH OF DIPHYODONTS. 311 anticipated, in a remarkable degree from that of the insectivorous kinds. The crushing instruments required for the food of the latter are not needed; and the true molars, 246 with their bristled crowns, are entirely absent in the Vampires (Desmodus), fig. 246. The teeth, at the fore-part of the mouth, are espe- cially developed, and fashioned for the inflic- tion of a deep and clean triangular puncture, like that made by a leech. The incisors are skuii and Teeth of the vam- 11 - -, iiire-Bat (Desmodus Vampirus). two in number above, closely approximated, one in each premaxillary bone, with a very large, compressed, curved, and sharp-pointed crown, implanted by a strong fang which extends into the maxillary bone. The upper canines have similar large lancet-shaped crowns, and their bases touch those of the in- cisors. In the lower jaw the incisors are two in number on each side, much smaller than the upper pair, and with bilobed crowns. The lower canines are nearly equal in size to those above, and have similar piercing trenchant crowns. The molar series is reduced above to two very small teeth, each with a simple compressed conical crown, implanted by a single fang. The first two molars below resemble those above ; but they are followed by a third, which has a larger compressed and bilobed crown, implanted by two fangs. This tooth corresponds with the last premolar in the more normal genera. The dental formula of the true Desmodus is thus reduced to- . 1.1 1.1 2.2 Z 2.2 ;C 1.1^3-3 = 2 ' The opposite extreme which the aberrant varieties of the Chei- ropterous dentition attain is manifested in the great frugivorous Bats : these constitute the genus Pteropus ; their dental formula is .2.2 1.1 2.2 3.3 Z 2^ ;C n ; P373 ;m 3.3 = 34 - (vol. ii. p. 388, fig. 252) : their molars have broad flat crowns. In some African Pteropi (Pt. macroceplialus and Pt. Whitei) the last small molar would seem to be wanting in both upper and lower jaws. The deciduous teeth make their appearance above the gum in Bats, as in Shrews, before birth ; but they attain a more completely developed state, and are retained until a short time after birth, when they are shed. The Colugos (Galeopithecus) resemble the Bats in the great expanse of their parachute, formed by the fold of integument extending on each side from the fore to the hind extremity, and 312 ANATOMY OF VERTEBRATES. in the incompleteness of the rim of the orbit (vol. ii. p. 388, fig. 253, A). The dental formula of the genus is 247 The two anterior incisors of the upper jaw are separated by a wide interspace. In the Phi- lippine Colugo they are very small, with simple sub-bilobed crowns ; but in the common Co- lugo (Lemur volans, Linn.; Ga- leopithecus Temminckii, Wat.) their crown is an expanded plate with three or four tuber- cles ; the second upper incisor presents the peculiarity of an insertion by two fangs in both species of Galeopithecus. In the lower jaw the crowns of the first two incisors, z, pre- sent the form of a comb, and are in this respect unique in the class Mammalia. Fig. 249 shows a section of one of these teeth magnified. This singular form of tooth is produced by the deeper extension of the marginal notches on the crown, analogous to those on the edge of ~ o the new-formed human incisor, and of those of certain Shrews, the notches being more nu- merous as well as deeper. Each of these broad pec- tinated teeth is implanted by a single conical fang, and is excavated by a pulp- cavity, which divides into as many canals as there are divisions of the crown, one being continued up the centre of each to within a short distance of its apical extremity. The medullary canal or branch of the pulp-cavity is shown in some of the divi- sions of the crown, at p. Each division has its proper investment of enamel, e, which substance is continued for a short distance upon the common base. The deciduous teeth appear not to cut the gum before birth, as Upper jaw and teeth, Galcopilhecus. 218 Lower jaw and teetli, Galeojnthccun. TEETH OF DIPHYODONTS. 313 they do in the true Bats. In a foetus of Galeopithecus Tem- minckii, with a head one inch and a half in length, I found the calcification of the first incisor just commenced in the closed alveolus, the second incisor 249 and the rest of the decidu- ous series being represented by the vascular uncalcified matrices. The upper milk teeth consist of two incisors, p a canine, and two molars, which latter are displaced and succeeded by the two premolars. The deciduous teeth are six in number in the lower jaw, the incisors being pectinated, but much smaller than their succes- sors. The true molars are developed and in place be- fore the deciduous teeth are shed. E. Quadrumana. In entering upon the dentition of the Quadrumanous order, we pass from that of the Insectivora by the Colugo, and seem to quit the Rodentia by the Aye-aye ( Chiromys). In this genus of the Lemurine animals, as in Phascolomys amongst the Marsupials, Desmodus amongst the Bats, and Sorex amongst the Insectivores, the dentition is modi- fied in analogical conformity with the Rodent type, to which, in the present instant, it makes a very close approximation, the canines being absent, and a wide vacancy separating the single pair of large curved scalpriform incisors in each jaw from the short series of molars. The upper incisors (vol. ii. p. 513, fig. 343, 22) are curved in the segment of a circle, and deeply implanted. The short exserted crowns touch one another, their simple widely exca- vated fangs diverging as they penetrate the substance of the jaw. These crowns also project obliquely forward, and do not extend vertically downward, as in the true Rodentia. The lower inci- sors are more depressed, and of greater breadth from before back- ward, than the upper ones. They are more curved than in the Rodentia, describing a semicircle, three-fourths of which are Section of lower incisor, Galeopithecus, magnified, v. 314 ANATOMY OF VERTEBRATES. lodged in the socket, which extends backward beyond the last molar tooth to the base of the coronoid process. The most im- portant character by which the incisors of this anomalous Lemur differ from those of the Rodentia is the entire investment of ena- mel, which is, however, thicker upon the front than upon the back part of the tooth. The molar teeth are four on each side of the upper jaw, and three on each side of the lower jaw, implanted vertically and in parallel lines. The molars are of simple struc- ture, with a continuous outer coat of enamel, and a flat subelliptic grinding surface. The upper ones are of unequal size, the first being the smallest, and the second the largest. In the lower jaw the inequality is less, and the last molar is the least. The first and last molars above have but one root; the second and third have each three roots. The first lower molar has two roots ; the second and third have each a single root. The adult dental formula is- 1.1 o 1.1 3.3 The deciduous dentition is .2.2 z n ;c 250 The second upper incisor and canine, and the lower milk-molar, all which are very minute, are not replaced ; the first true or perma- nent molar follows so speedily the deciduous one that, being ' in place ' therewith, it has been reckoned with the milk-dentition. 1 The lower jaw is modified to give strength to the muscles wielding the enormous and powerful incisors by the low position of the condyle, analo- gous to that in Plagiaulax and other carnivorous Mammals, contrasting with its high posi- tion in true Rodents and Kan- garoos. The Avahi, or woolley Le- mur (I^ichanotus laniger, fig. 250), has the incisors of the lower jaw large and limited to a single pair, but far from show- ing the proportions of those in Chiromys : the upper incisors are in two pairs, as in the milk-dentition in Chiromi/s, and are small. The dental formula in the Slow Lemurs (Stenops, Tarsius) is- .2.2 1.1 3.3 3.3 ' 2.2 5C T.I ; ^373 ^Sl^ 36 ' The first upper incisor is larger than the second. 1 CXXIl". Dentition of \Vnullcy Lemur. TEETH OF DIPHYODONTS. 315 Qtolicnus and Lemur have the same number and kinds of teeth. In the upper jaw the incisors are small and vertical ; the two on the right side are separated by a wide space from the two on the left. The lower canines are compressed and procum- bent like the incisors, but are a little larger. The upper canine is long, curved, compressed, sharp-edged, and pointed. The three upper premolars have the outer part of the crown pro- longed into a compressed pointed lobe, whilst the inner part forms a tubercle, which is largest in the third. In the true molars the inner division of the crown is so increased as to give it a quadrate form, the outer division being divided into two pointed lobes. The premolars below are long, and the molars 4-cuspid in Otolicnus. All the American Quadrumana are distinguished from the Apes and Monkeys of the Old World by the superior number of the premolars, and, by this resemblance to the Lemurs, they show their inferior position in the zoological scale. The small ( Mar- mosets,' however, forming the genera Hapale and Midas, have but two true molar teeth on each side of both jaws, their dental formula being- .2.2 l.l 3.3 22 1 2^2 5 C l7i ;/) 3^3*' m 272 The lemurine character of the long, narrow, inferior incisors con- tinues to be manifested by the Sakis (Pitkecia 111.), which, like the larger species of Platyrhines called Howlers, Capuchins, and Spider-Monkeys, have the normal number of true molar teeth in the Quadrumanous order, their dental formula being- .2.2 1J 3.3 3.3 1 2~2 5 *' T7i ;/? 373 ; m 33 '' The Capuchin Monkeys ( Cebus, vol. ii. fig. 349) have the four lower incisors broad, thick, and wedge-shaped a form which these teeth retain, with slight modi- fications, throughout the Quadru- manous order. The canines are sufficiently developed to inflict se- vere wounds. The first three of the molar series, />, 2, 3, 4, are bicuspid premolars; the rest, m, i, 2, 3, are quadricu spid true molars. The de- ciduous formula is . 2.2 1.1 3.3 TV c\ " -i i ji i i Deciduous aud permanent teeth of a young Jb ig. 2ol shows the deciduous series, cebus A^iia. CLXXH". 316 ANATOMY OF VERTEBRATES. d i. . .. d 4, in place, together with the first of the permanent true molars, m, i ; the germs of the rest of the permanent teeth are exposed in the upper jaw. In the Catarhine division of the order, the first or deciduous dentition consists of- .2.2 1.1 2.2 '22 ;C l7T ;m 2^ = 2 - The two milk molars are displaced and succeeded vertically by the two bicuspid premolars, and are followed horizontally by three true molars on each side of both upper and lower jaws. The permanent formula in all the Old World Qnadrumana is .2.2 1.1 2.2 3.3 The incisors have always a shape conformable to their name, 250 but are very thick and strong ; in the upper jaw the middle are larger than the lateral ones, and both are larger than those below. The canines are coni- cal, pointed, with trenchant pos- terior margins, always longer than the adjoining teeth, and acquiring, in the males of the Catarhine dentition (Papto). T i i r\ , i great Joaboons and Urangs, the proportions of those teeth in the Carnivora. The Mandrills Papio maimon (fig. 252) have these dental weapons most formidable for their size and shape ; especially the upper pair, which descend behind the crowns of the lower canines, and along the outside of the first lower premolars, the crowns of which seem as if bent back by the action of the upper canines ; the anterior longitudinal groove of these teeth is very deep, their posterior margin very sharp. A long diastema divides the upper canine from the inci- sors, a short one separates it from the premolars ; these and the three true molars are arranged in a straight line. In the Orang-utan (Pit/iecus Wiirmlii), vol. ii. p. 534, fig. 355, the thickness of the base of the crown of the upper middle incisors equals the breadth of the same ; and they are double the size of the lateral incisors. The abraded surface of the front incisors in the old Orang forms a broad tract extending obliquely from the cutting edge to the back part of the base of the crown ; the lateral incisors are more pointed, the outer angle being ob- liquely truncated ; a vacant space of their own breadth divides them from the canines. These, in the male Orang, have a long TEETH OF DIPHYODONTS. 317 and strong slightly-curved crown, extending below the alveolar border of the under jaw when the mouth is shut, with a moderately sharp posterior margin, but without an anterior groove. In the female Orang the canines are smaller ; the crowns extend only a short distance beyond the level of the adjoining molars. In the upper jaw both premolars and molars are im- planted by three diverging roots, two external and one internal ; in the lower jaw the corresponding teeth have two strong di- verging roots ; the series of grinders forms a straight line on each side of both jaws. As the precise characteristics and ordinal distinction of the human dentition are best demonstrated by comparison with that brute species which is most nearly allied to man, the details of such a comparison will here be given and illustrated more fully, as manifested in the Gorilla ( Troglodytes Gorilla). Fig. 253 gives a side view of the teeth of a male full-grown, but not aged, O O -* O - 7 specimen of this species. In the upper jaw the middle incisors are smaller, the lateral ones i, 2, larger than those of the Orang ; they are thus more nearly equal to each other ; nevertheless the proportional superiority of the middle pair is much greater than in Man, and the proportional size of the four incisors both to the entire skull and to the other teeth is greater. Each incisor has a prominent posterior basal ridge, and the outer angle of the lateral incisors i, 2, is rounded off as in the Orang. The incisors incline forward from the vertical line as much as in the Orano*. e> Thus the characteristics of the human incisors are, in addition to their true incisive wedge-like form, their near equality of size, their vertical or nearly vertical position, and small relative size to the other teeth and to the entire skull. The diastema between the incisors and the canine on each side is as well marked in the male Gorilla as in the male Orang. The crow r n of the canine, fig. 253, c, passing outside the interspace between the lower canine and premolar, p 3, extends in the male Troglodytes Gorilla a little below the alveolar border of the under jaw when the mouth is shut ; the upper canine of the male Troglodytes niger likewise projects a little below that border. In the male of the Chimpanzee ( Troglodytes niger\ the upper canine is conical, pointed, but more compressed than in the Orang, and with a sharper posterior edge ; convex anteriorly, becoming flatter at the posterior half of the outer surface, and concave on the cor- responding part of the inner surface, which is traversed by a shallow longitudinal impression ; a feeble longitudinal rising and a second linear impression divide this from the convex anterior 318 ANATOMY OF VERTEBRATES. surface, which also bears a longitudinal groove at the base of the fj CJ crown. The canine is rather more than twice the size of that 253 Dentition of an adult male Troglodytes Gorilla, nat. size. cm'. 254 Dentition of an adult female Gorilla, uat. size. cm'. in the female. In the male Gorilla the canine is more in- clined outward ; the anterior groove 011 the inner surface of the TEETH OF DIPHYODONTS. 319. crown is deeper, the posterior groove is continued lower down upon the fang, and the ridge between the two grooves is more prominent than in the Troglodytes nicjer. Both premolars, 255 m 7> W'2 Dentitiiiii c.f uj4M-r ja\v, in.-ilc Ti-t> ; /l, n!n, nat. sixe. cm'. fig. 255, p 3, and p 4, are bicuspid ; the outer cusp of the first, and the inner cusp of the second being the largest, and the first premolar, p 3, consequently appearing the largest on an external view. The difference is well marked in the female, fig. 254, p 3. The anterior external angle of the first premolar is not produced as in the Orang, which in this respect makes a marked approach to the lower Quadrumana. In Man, where the outer curve of the premolar part of the dental series is greater than the inner 320 ANATOMY OF VERTEBRATES. one, the outer cusps of both premolars are the largest ; the alternating superiority of size in the Gorilla accords with the straight line which the canine and premolars form with the true molars. In fig. 255, m i, m 2, m 3, are quadricuspid, relatively larger in comparison with the bicuspids than in the Orang. In the first and second molars of both species of Troglodytes a low ridge connects the antero-internal with the postero-external cusp, crossing the crown obliquely, as in Man. There is a feeble indication of the same ridge in the unworn molars of the Orang ; but the four principal cusps are much less distinct, and the whole grinding surface is flatter and more wrinkled. In Troglodytes niger the last molar is the smallest, owing to the inferior develop- ment of the two hinder cusps, and the oblique connecting ridge is feebly marked. In Troglodytes Gorilla this ridge is as well developed as in the other molars, but is more transverse in position ; and the crown of m 3 is equal in size to that of m i or m s, having the posterior outer cusp, and particularly the pos- terior inner cusp, more distinctly developed than in Troglodytes niger. The repetition of the strong sigmoid curves which the unworn prominences of the first and second true molars present in Man, is a very significant indication of the near affinity of the Gorilla as compared with the approach made by the Orangs or any of the inferior Quadrumana, in which the four cusps of the true molars rise distinct and independently of each other. A low ridge girts the base of the antero-internal cusp of each of the upper true molars in the male Chimpanzees ; it is less marked in the female. The premolars as well as molars are severally im- planted by one internal and two external fangs. In no variety of the human species are the premolars normally implanted by three fangs ; at most the root is bifid, and the outer and inner divisions of the root are commonly connate. It is only in the black varie- ties, and more particularly that race inhabiting Australia, that I have found the ' wisdom-tooth,' fig. 257, m 3, with three fangs as a general rule ; and the two outer ones are more or less confluent. The lower canine of the male (figs 253, 256, c), shows the same relative superiority of size as the upper one, compared with that in the female, in both species of Troglodytes. The canine almost touches the incisor, but is separated by a diastema one line and a half broad from the first premolar. This tooth p 3, is larger ex- ternally than the second premolar, and is three times the size of the human first premolar, fig. 257, p 3 ; it has a subtriedral crown, with the anterior and outer angle produced forward, slightly indicating the peculiar features of the same tooth in the TEETH OF DIPHYODONTS. 321 Baboons, but in a less degree than in the Orang. The summit of the crown of p 3 terminates in two sharp triedral cusps the outer one rising highest and the second cusp being feebly in- dicated on the ridge extending from the inner side of the first ; the crown has also a thick ridge at the inner and posterior part of its base. The second premolar, p 4, has a subquadrate crown, with the two cusps developed from its anterior half, and a third smaller one from the inner angle of the posterior ridge. Each lower premolar is implanted by two aritero-posteriorly compressed divergent fangs, one in front of the other, the anterior fang being the largest. The three true molars are nearly equal in size in the Troglo- dytes Gorilla, the last being a little larger than the first : in the Troglodytes niger, fig. 256, the first, m i, is a little larger than the last, m 3, which is the only molar in the smaller Chimpanzee as large as the corresponding tooth in the black varieties of the human subject, in most of which, especially the Australians, fig. 257, the true molars attain larger dimensions than in the yellow or white races. The four principal cusps, especially the two inner 256 Teeth of right side, lower jaw, of adult male Chimpanzee, (Troglodytes niger), nat. size. ones of the first molar of both species of Troglodytes, are more pointed and prolonged than in Man ; a fifth small cusp is deve- loped behind the outer pair, as in the Orangs and the Gibbons, but is less than that in Man. The same additional cusp is pre- sent in the second molar, which is seldom seen in Man. The crucial groove on the grinding surface is much less distinct than in Man, not being continued across the ridge connecting the anterior pair of cusps in the Chimpanzee. The crown of the third molar is longer antero-posteriorly from the greater develop- ment of the fifth posterior cusp, which, however, is rudimental in comparison with that in the Semnopitheques and Macaques. VOL, III. Y 322 ANATOMY OF VERTEBRATES. the three true molars are supported by two distinct and well- developed antero-posteriorly compressed divergent fangs ; in the white and yellow races of the human subject these fangs arc usually connate in m 3; and sometimes also in m 2. The molar series in both species of Troglodytes forms a straight line, with a slight tendency, in the upper jaw, to bend in the opposite direc- tion to the w T ell-marked curve which the same series describes in the human subject. This difference of arrangement, with the more complex implan- tation of the premolars, the proportionally larger size of the incisors as compared with the molars ; the still greater relative magnitude of the canines; and, above all, the sexual distinction in that respect illustrated by figs. 253 and 254, stamp the Gorillas and Chim- panzees, fig. 256, most decisively with not merely specific but generic distinctive characters as compared with Man. For the teeth are fashioned in their shape and proportions in the dark recesses of their closed formative alveoli, and do not come into the sphere of operation of external modifying causes until the full size of the crowns has been acquired. The formidable natural weapons of the males of both species of Troglodytes, form the compensation for the want of that psychical capacity to forge or fashion de- structive instruments which has been reserved, as his exclusive prerogative, for Man. Both Chimpanzees and Orangs differ from the human subject in the order of the development of the perma- nent series of teeth ; the second molar, m 2, comes into place before either of the premolars has cut the gum, and the last molar, m 3, is acquired before the canine. We may well suppose that the larger grinders are earlier required by the frugivorous Chim- panzees and Orangs than by the higher organised omnivorous and longer nursed Bimanal, with more numerous and varied re- sources, and probably one main condition of the earlier develop- ment of the canines and premolars in Man may be their smaller relative size. r. Bimana. Having reached, in the Gorilla, the highest step in the series of the brute creation, our succeeding survey of the dental system, cleared and expanded by retrospective comparison, becomes fraught with peculiar interest, since every difference so detected establishes the true and essential characteristics of that part of man's frame. The human teeth are the same in number and in kind as those of the catarhine Quadrumana. The bimanal dental formula is therefore .2.2 1.1 2.2 3.3 TEETH OF DIPHYODONTS. 323 that is to say, there are on each side of the jaw, both above and be- low, two incisors, one canine, two premolars, and three true molars. They are more equal in size than in the Quadrumana. No tooth surpasses another in the depth of its crown ; and the entire series, which describes in both jaws a regular parabolic curve, is uninter- rupted by any vacant space (vol. ii.,fig. 182). The most marked distinction between the bimanal dentition and that of the highest Quadrumanals, is the absence of the interval between the upper lateral incisor and the canine, and the comparatively small size of the latter tooth ; but its true character is indicated by the conical form of the crown, which terminates in an obtuse point, is convex outward, and flat or sub-concave within, at the base of which surface there is a feeble prominence. The conical form is best expressed in the Melanian races, especially the Australian, fig. 257, c. The canine is more deeply implanted, and by a stronger fang than the incisors ; but the contrast with the Chimpanzee is sufficiently manifest, as is shown in fig. 256, c. There is no sexual 257 Dentition, lower jaw, of male Australian. superiority of size either of the canine or any other single tooth in the human subject. 1 1 In honest argument as to Man's place in Nature, his zoological characters are to be compared with those of the brute that comes nearest to him ; the differences so established should be contrasted with those between such brute, the gorilla, e.g., and the next step in the scale, the chimpanzee, e.g.; and so on, step by step, through the order which Zoology forms of the series of species so gradually differentiated. No doubt a gorilla differs more in its dentition from a lemur, and still more from a mole or a mouse, than it differs from Man. Take another character the hinder or lower limbs, e.g.; contrast the Negro in this respect with the gorilla, and, next, that ape with any other quadrumanal. Much as the aye-aye differs as a whole, from the gorilla, it does resemble it more in such quadrumanal structure than the gorilla resembles Man. Between the two extremes of the four-handed series there is greater organic con- formity in the main ordinal character than exists between the highest ape and the lowest man. Or take the cerebral test. Man's place in the Natural System is to be judged, not by the degree of difference between the brain of an ape and that of a mammal one hundred links removed ; but by the degree of difference between the human brain and that of the brute which comes nearest to him, as contrasted with the degree of difference between the brains of the gorilla and chimpanzee, or between those of any other two conterminous species constituting links in the quaclrumanous chain. The difference between figs. 147 and 148-9 may be greater than between 149 Y 2 324 ANATOMY OF VERTEBRATES. Both upper and lower premolars, fig. 257, p 3 and 4, are bicuspid; they are smaller in proportion to the true molars than in the Chimpanzee and Orang. In the upper premolars a deep straight fissure at the middle of the crown divides the outer and larger from the inner and smaller cusp ; in the lower premolars the boun- dary groove describes a curve concave towards the outer cusp, and is sometimes obliterated in the middle by the extension of a ridge from the outer to the inner cusp, which cusp is smaller in proportion than in the upper premolars. These teeth in both jaws are apparently implanted each by a single, long, subcom- pressed, conical fang ; but that of the upper premolars is shown by the bifurcated pulp-cavity to be essentially two fangs, connate, and which, in some instances, are separated at their extremities. The crowns of the true molars, fig. 257, m i, 2, 3, are larger in pro- portion to the jaws, are a little larger in proportion to the bicuspids, and still more so in proportion to the canine and incisor teeth, than in the Chimpanzees and Orangs. The contour of the grinding surface is more rounded, and the angles of the crown are less marked in the higher than in the lower Quadrumana. The first and second true molars of the upper jaw support four triedral cusps ; the internal and anterior one is the largest, and is connected with the external and posterior cusp by a low ridge extending obliquely across the grinding surface, with a deep depression on each side of it ; the anterior groove extending to the middle of the outer surface, the posterior one to the inner sur- face. The enamel is first worn away by mastication from the anterior and internal or largest tubercle ; a line of enamel extending from the outside to the middle of the crown is the last to be removed before the grinding surface is reduced to a field of den- tine with a simple ring of enamel. It is worthy of remark, that by the time when the permanent teeth have come into place, the first true molar in both jaws is more worn, as compared with the second and third molars, than it is in the Chimpanzee or Orang, owing to the slow attainment of maturity characteristic of the human species, and the longer interval which elapses between the acquisition of the first and the last true molars, than in the highest Quadrumana. In the last true molar, called from its late appearance the ' dens sapiential,' or wisdom-tooth, the two inner tubercles are blended together, and a fissure extends in many and 150 (vol. ii.); but truth compels the remark that the lemur and ape are sepa- rated by numerous gradation al species ; whilst between the ape and man there is no known connecting or intermediate link. Logicians have long ago exposed and branded the sophism which has of late been propounded to persuade men that they are of the order of apes. TEETH OF DIPHYODONTS. 325 instances, especially in the Melanian varieties, from the middle of the grinding surface, at right angles to that dividing the two O O O O O outer cusps, to the posterior border of the tooth. The first upper molar is always implanted by three diverging fangs, two external and one internal. The second molar is ~ ' usually similarly implanted, but the two outer fangs are less divergent, are sometimes parallel, and occasionally connate ; this variety appears to be more common in the Caucasian than in the Melanian races ; and in the Australian skulls the wisdom tooth usually presents the same three- fanged implantation as in the Chimpanzee and Orang. The crowns of the inferior true molars are quinque-cuspid, the fifth cusp being posterior and connected with the second outer cusp : it is occasionally obsolete in the second molar. The four normal cusps are defined by a crucial impression, the posterior branch of which bifurcates to include the fifth cusp ; this bifurca- tion being most marked in the last molar where the fifth cusp is most developed. In the first molar a fold of enamel, extending from the inner surface to the middle of the crown, is the last to disappear from the grinding surface in the course of abrasion. The wisdom-tooth, fig. 257, in 3, is the smallest of the three molars in both jaws, but the difference is less in the Melanian than in the Caucasian races. Each of the three lower molars is inserted by two sub-compressed fangs, grooved along the side, turned towards each other. This double implantation appears to be constant in the Melanians, especially the Australian race, in which the true molars are relatively larger than in other blacks. In Europeans it is not unusual to find the two fangs in both the second and third molars connate along a great part or the whole of their extent. With respect to the reciprocal apposition of the teeth of the upper and under jaw, it is interesting to observe that the crown of the lower canine is, as usual, in advance of that above, and fits into the shallow notch between that and the lateral incisor. The inferior incisors are so small that their anterior surface rests against the posterior surface of the upper ones when the mouth is closed ; the other teeth are opposed crown to crown, the upper teeth extending a little more outwardly than the lower ones. The deciduous series of teeth in the human subject, fig. 258, consists of .2.2 1.1 2.2 '^ ;C Li ;m 2T2 =20 ' The upper milk incisors of the Chimpanzee are relatively larger 326 ANATOMY OF VERTEBRATES. 258 nil in than in Man, especially the middle pair; but the dispropor- tionate size of these is still more manifest and characteristic of the Orang. The crown of the canine is longer and more pointed in the Chimpanzee than in Man; still more so, and further apart from the incisor in the Orang. The first milk-molar, fig. 258, d 3, in the human subject is more similar in shape and size to the second, d 4, than it is in either the Chimpanzee or Gorilla : in which it is relatively smaller, showing in the lower jaw a subcom- pressed triangular crown. /03 P Deciduous and permanent teeth, Human Child : set. 6i. The eruption of the human milk-teeth usually begins in the infant of seven months old, and is completed about the end of the second year; those of the lower jaw preceding the 259 d d Highly-magnified section of dentine and cement, from the fang of a Human molar, v, pi. 123. upper. The average periods of the appearance of both decidu- ous and permanent teeth are as follows :- Permanent teeth. 6^ years, first molar, m 1, (fig. 258). 7th year, mid-incisor, i 1. 8th year, lat. -incisor, i 2. 9th year, first bicuspid, p 3. 10th year, second bicuspid, p 4. llth to 12th year, canine, c. 12th to 13th year, second molar, m 2. 17th to 21st year, third molar, m 3. The structure of human dentine is exemplified in fig. 259. Deciduous teeth. 7th month, mid-incisor, d i 1. ib. to 10th month, lat. -incisor, d i 2. 12th to 14th month, first molar, d 3. 14th to 20th month, canine, d c. 18th to 36th month, second molar, d 4. TEETH OF DIPHYODONTS. 327 2GO The dentinal tubes, d, d, send off ramuli into the inter-tubular tissue, and terminate either by anastomotic loops, or in the irregular vacuities or cells at the periphery of the dentine. The dentinal compartments, or indications of the original cells of the dentinal pulp, are shown at a, b ; the modified peripheral layer of the dentine, remarkable for its superior sensibility, at g. The layer of cement, h, which covers the dentine of the fang, is seldom so thick as to show a bone-cell, in human teeth. The structure of the dentine relates, in regard to the curvilinear compartments, , b, to the steps in its formation ; and, in regard to its tubular columns, to the strength of the tooth and its vitality ; the latter important property depending on the percolation of the plasma through the delicate cellular sructure of the filamentary pro- longations of the pulp, so far as they may extend along the tubuli. The sensibility of the dentine is due to concomitant productions of neurine ; but the distinct tubules are not large enough to O C5 admit capillary vessels with red particles of blood, and the tissue above described has consequently been termed e un- yascular dentine.' G. Carniuora. The feline denti- tion is the best for flesh-food. The canines, fig. 260, c, are of great strength, deeply implanted in the jaw, with the fangs thicker and longer than the enamelled crown; this part is conical, slightly recurved, sharp-pointed, convex in front, with one or two longitudinal grooves on the outer side, almost flat on the inner side, and with a sharp edge behind. The lower canines pass in front of the upper ones when the mouth is closed. The incisors, six in number on both jaws, form a trans- verse row ; the outermost above, ib. i y is the longest, resembling a small canine ; the intermediate ones have broad and thick crowns indented by a transverse cleft. The first upper premolar, p 2, is rudimental ; there is no answerable tooth in the lower jaw. The second, p 3, in both jaws, has a strong conical crown sup- ported on tAvo fangs. The third upper tooth, p 4, has a cutting or trenchant crown divided into three lobes, the last being the largest, Dentition of Lion. 328 ANATOMY OF VERTEBRATES. and with a flat inner side, against which the cutting tooth, m i, in the loAver jaw works obliquely. Behind, and on the inner side of the upper tooth, p 4, there is a small tubercular tooth. The feline dental formula is .3.3 1.1 3.3 3.3' " 1.1' P 2.2' 1.1 TO = 30. 261 A glance at the long sub -compressed, trenchant, and sharp- pointed canines, suffices to appreciate their peculiar adaptation to seize, to hold, to pierce, and lacerate a struggling prey. The co-adaptations of jaws and skull are given in vol. ii. p. 505. The use of the small pincer-shaped incisor teeth is to gnaw the soft, gristly ends of the bones, and to tear and scrape off the tendinous attachments of the muscles and periosteum. The compressed trenchant blades of the sectorial teeth play vertically upon each other's sides like the blades of scissors, serving to cut and coarsely divide the flesh ; and the form of the joint of the lower jaw almost restricts its movement to the vertical direction, up and down. The wide and deep zygomatic arches, fig. 260, 27, and the high crests of bone upon the skull, ib. 3, 7, con- cur in completing the carnivorous physiog- nomy of this most formidable existino; o species of the feline tribe. The penultimate tooth in the upper jaw, fig. 260, p 4, and the last tooth in the lower jaw, ib. m i, were denominated by F. Cuvier ' dent car- nassiere,' which has been rendered ' dens sectorius,' the ' secto- rial,' or scissor-tooth. It preserves its cha- racteristic form only in the strictly flesh- feeding genera, in which is seen the part called the ( blade,' and that called the ( hump ' or tubercle. In Felis the lower sectorial Deciduous dentition, Young Lion. TEETH OF DIPHYODONTS. 329 (fig. 261, m i) consists exclusively of the blade, and plays upon the inside of that of the upper l sectorial.' This tooth, fig. 261, p 4, above, succeeds and displaces a deciduous tubercular molar, ib. d 4, in all Carnivores, and is therefore a ' premolar ; ' the lower sectorial, ib. m i, comes up behind the deciduous series, d 3, d 4, and has no immediate predecessor ; it is, therefore, a true molar, and the first of that class. By these criteria the sectorial teeth may always be distinguished under every transitional variety of form which they present in the carnivorous series, from Ma chair odus, fig. 293, iv., in which the crown consists exclusively of the f blade' in both jaws, to Ursus, ib. II., in which it is totally tubercular ; the development of the tubercle bearing an inverse relation to the carnivorous propensities of the species. The dentition of the hyasna resembles the feline in the reduc- tion of the tubercular molars to a single minute tooth on each side of the upper jaw, and in the inferior molars being all conical or sectorial teeth ; but the molar teeth in both jaws are larger and stronger, and the canines smaller in proportion, than in Felines, from the formula of which the dentition of the hyaena differs numerically only in the retention of an additional premolar tooth, p i above and^? 2 below, on each side of both jaws : it is .3.3 1.1 4.4 1.1 Z 3T3 ;C n ; ^373 ;Wi lTl =34 - The crowns of the incisors form almost a straight transverse line in both jaws, the exterior ones, above, being much larger than the four middle ones, and extending their long and thick inserted base further back ; the crown of the upper and outer incisor is strong, conical, recurved, like that of a small canine. The four intermediate small incisors have their crown divided by a trans- verse cleft into a strong anterior, conical lobe, and a posterior ridge, which is notched vertically ; giving the crown the figure of a trefoil. The lower incisors gradually increase in size from the first to the third ; this and the second have the crown indented externally ; but they have not the posterior notched ridge like the small upper incisors ; the apex of their conical crown fits into the interspace of the three lobes of the incisor above. The canines have a smooth convex exterior surface ; the inner surface is almost flat and of less relative extent in the inferior canines. The first premolar above is very small, with a low, thick, conical crown ; the second presents a sudden increase of size, and an addition of a posterior and internal basal ridge to the strong cone. The third premolar exhibits the same form on a still larger scale, and is remarkable for its great strength. The posterior part of the cone 330 ANATOMY OF VERTEBRATES. of each of these premolars is traversed by a longitudinal ridge. The fourth premolar above is the carnassial tooth, and has its long blade divided by two notches into three lobes, the first a small thick cone, the second a long and compressed cone, the third a horizontal, sinuous, trenchant plate ; a strong tri- cdral tubercle, t, is developed from the inner side of the base of the anterior part of the crown. The single true molar of the upper jaw is a tubercular tooth of small size. The first premolar of the lower jaw fits into the interspace between the first and second premolars above, and answers, therefore, to the second lower premolar in the Viverridce. The second is the largest of the lower premolars ; its crown forms chiefly a strong rounded cone, girt by a basal ridge, and might serve as the model of a hammer for breaking stones. The last lower tooth is the sectorial,' as in Felis. The deciduous teeth consist of .3.3 1.1 3.3 Z 3^ ;c n ;m 3^ = 28 - The permanent dentition of the Hy&na assumes those charac- teristics which adapt it for the peculiar food and habits of the adult : of these the chief is the great size and strength of the molars as compared with the canines, and more especially the thick and strong conical crowns of the second and third premolars in both jaws, the base of the cone being belted by a strong ridge which defends the subjacent gum. This form of tooth is especially adapted for gnawing and breaking bones, and the wdiole cranium has its shape modified by the enormous development of the muscles which work the jaws and teeth in this operation. Adapted to obtain its food from the coarser parts of animals which are left by the nobler beasts of prey, the hyaena chiefly seeks the dead carcass, and bears the same relation to the lion which the vulture does to the eagle. The family Viverridce, which comprehends the Civets, Genets, Ichneumons, Musangs, Surikates, and Mangues, is characterised, with few exceptions, by the following formula :- .3.3 1.1 4.4 2.2 Z 373 ;C L1^474 ;7n 272 =4a It differs from that of the genus Canis by the absence of a tuber- cular tooth, m 3, on each side of the lower jaw ; but, in thus making a nearer step to the feline dentition, the Viverridce, on the other hand, recede from it by the less trenchant and more tuber- cular character of the sectorial teeth. The canines are more feeble, and their crowns are almost TEETH OF DIPHYODONTS. 331 smooth ; the premolars, however, assume a formidable size and shape in some aquatic species, as those of the sub-genus Cynogale, in which their crowns are large, compressed, triangular, sharp- pointed, with trenchant and serrated edges, like the teeth of certain sharks (whence the name Squalodon, proposed for one of the species), and well adapted to the exigencies of quadrupeds subsisting principally on fish ; the opposite or obtuse, thick form of the premolars is manifested by some of the Musangs, e.g. Paradoxurus auratus. The deciduous dentition consists, in the Yiverrine family, of- .3.3 1.1 3.3 Z 3T3 ;C Li ;W 3r3 =28 - The interlocking of the crowns of the teeth of the upper and lower jaws, which is their general relative position in the Carni- vora, is well-marked in regard to the premolars of the Viverrida ; as the lower canine is in front of the upper, so the first lower pre- molar rises into the space between the upper canine and first upper prernolar ; the fourth lower premolar in like manner fills the space between the third upper premolar and the sectorial tooth, playing upon the anterior lobe of the blade of that tooth which indicates by its position, as by its mode of succession, that it is the fourth premolar of the upper jaw. The first true molar below, modified as usual in the Carnivora to form the lower sectorial, sends the three tubercles of its anterior part to fill the space between the sectorial and the first true molar above. In the Musangs, the lower sectorial is in more direct opposition to its true homotype the first tubercular molar in the upper jaw ; and these Indian Viverridce (Paradoxuri} are the least carnivorous of their family, their chief food consisting of the fruit of palm-trees, whence they have been called ( Palm-cats.' The normal dental formula of the genus Canis is The incisors increase in size from the first to the third; the trenchant margin of the crown is divided by two notches into a large middle and two small lateral lobes. The canines, c, are curved, sub-compressed; the enamelled pointed crown forms nearly half the length of the tooth, and is smooth, without any groove. The premolars, fig. 293, p 1-4, have strong sub-compressed conical crowns gradually enlarging from the first to the third, p 3, in the upper jaw, and to the fourth, p 4, in the lower jaw, and acquiring one or two accessory posterior tubercles as they increase in size. The fourth upper premolar, p 4, presents a sudden increase of 332 ANATOMY OF VERTEBRATES. size, with its sectorial form; its blade is divided into two cones by a wide notch, the anterior cone being the strongest and most produced ; the tubercle is developed from the inner side of the base of this lobe. The first and second upper molars, m i and 2, are tuberculate ; but the second is very small, less than half the size of the first molar. The first true molar below, m i, is modi- fied to form the opposing blade to the sectorial tooth above ; re- taining the tuberculate character at its posterior half. The blade is divided by a vertical linear fissure into two cones, behind which the base of the crown extends into a broad trituberculate talon. The second molar, m 2, has two anterior cusps on the same trans- verse line, and a posterior broad flat talon ; the last lower molar, m 3, is the smallest of all the teeth. The absence of a tuberculate molar in the lower jaw of the immature Dog, brings the character of the deciduous dentition of the genus Canis, fig. 262, closer to the permanent dentition of stricter carnivores, and affords an interesting illustration of the 262 1/12 Deciduous and permanent teeth in the Dog (Cam's). law that unity of organisation is manifested directly as the proximity of the animal to the commencement of its development. The succession of two tubercular molar teeth behind the perma- nent sectorial tooth in the permanent dentition of the lower jaw contributes to adapt the Dog for a greater variety of climates, of food, and of other circumstances, all of which tend, in an important TEETH OF DIPHYODONTS. 333 degree, to fit that animal for the performance of its valuable services to man. In no other genus of quadruped are the jaws so well or so variously armed with dental organs ; notwith- standing the extent of the series, the vacancies are only sufficient to allow the interlocking; of the strong canines. These are effi- O CJ cient and formidable weapons for seizing, slaying, and lacerating a living prey ; the incisors are well adapted, by their shape and advanced position, for biting and gnawing ; the premolars, and especially the sectorials, are made for cutting and coarsely dividing the fibres of animal tissues, and the tuberculate molars are as admirably adapted for cracking, crushing, and completing the comminution of the food, whether of animal or vegetable nature. The dentition of the Weasel tribe (Mustelida) is illustrated in fig. 293 IV., Mustela : the dental formula is .3.3 1.1 4.4 1.1 Z 3^ ;c n^3^ ;77l ^2 = 36 - The first premolar, p i, in the upper jaw, which is absent in the Polecat and Weasel, is retained in the Otter, and is placed on the inner side of the canine ; the sectorial premolar, p 4, has its inner lobe much more developed in Lutra than in Putorius, and the tubercular molar, ml, is relatively larger. Similar modifications of these teeth distinguish the dentition of the lower jaw of the Otter, which agrees in the number and kind of teeth with that of the Polecat. The increased grinding surface relates to the inferior and coarser nature of the animal diet of the Otter, the back teeth being thus adapted for crushing the bones of fishes before they are swallowed. In the Martin cats (Mustela), the little homotype of p \ above is present in the lower jaw ; in the bloodthirsty Stoats and Wea- sels, p i is absent in both jaws ; as it is likewise in the great Sea- otter (Enhydra), in which also the two middle incisors are wanting in the lower jaw. In this animal the second premo]ar, p 3, has a strong obtuse conical crown, double the size of that of p 2 ; the third premolar, p 4, is more than twice the size of p 3, and represents the upper carnassial or sectorial strangely modified ; the two lobes of the blade being hemispheric tubercles. The last tooth, m i, has a larger crown than the sectorial, and is of a similar broad crushing form. In the family Melida> is comprised the European (Meles), the Indian (Arctonyx), and the American ( Taxidea) Badgers, which, with respect to their dentition, stand at the opposite extreme of the Mustelida to that occupied by the predaceous Weasel, and 334 ANATOMY OF VERTEBRATES. manifest the most tuberculate and omnivorous character of the teeth. The formula is- .3.3 1.1 3.3 1.1 Z 3.3 ;C l.i ;/7 4.4 ;m 2.2 =36 - The canines are strongly developed, well pointed, with a poste- rior trenchant edge ; they are more compressed in Arctonyx than in Meles. The first lower premolar is very small, single-fanged, and, generally, soon lost. The first above, corresponding with the second in the Dog, is also small, and implanted by two con- nate fangs. The second upper premolar, p 3, has a larger, but simple, sub- compressed conical crown, and is implanted by two fangs. The third repeats the form of the second on a larger scale, with a better developed posterior talon, and with the addition of a trituberculate low flat lobe, which is supported by a third fang ; the outer pointed and more produced part of this tooth represents the blade of the sectorial tooth and the entire crown of the antecedent premolars. The true molar in Meles is of enormous size compared with that of any of the preceding Carnivora ; it has three external tubercles, and an extensive horizontal surface traversed longitudinally by a low ridge, and bounded by an internal belt, or ( cingulum.' In other allied genera, which, like the badgers, have been grouped, on account of the plantigrade structure of their feet, with the bears, a progressive approximation is made to the type of the dentition of the Ursine species. The first true molar below soon loses all its sectorial modification, and acquires its true tubercular character ; and the last premolar above becomes more directly and completely opposed to its homotype in the lower jaw. The Racoon (Procyon), and the Coati (Nasua), present good examples of these transitional modifications ; they have the complete number of premolar teeth, the dental formula being- .3.3 1.1 4.4 2.2 *3-3 ;C T7r^474 ;m 2T2 = 40 ' That of the Benturong (Arctictis) and Kinkajou ( Cercoleptes) is- .3.3 1.1 3.3 2.2 Z 373 ;C L1^3T3 ;m 272 = 36 - The lower canine of Nasua has a deep longitudinal groove on the inner side of the crown. In Ailurus both upper and lower canines present two longitudinal grooves. In Cercoleptes a longitudinal ridge divides the two grooves on the canines. A fossil canine tooth from the eocene sand at Kyson presents a still greater number of grooves and ridges, whence the name Pricynodon. The essential characteristic of the dentition of the Bears, fig. TEETH OF DIPHYODONTS. 335 340, vol. ii. ( Ursus) is the development, in the lower jaw, of the true molar teeth to their typical number in the placental Mam- malia, and their general manifestation, in both jaws, of a tuber- culate grinding surface ; the premolar teeth are much reduced both in size and number. In the frugivorous Bears of India and the Indian Archipelago, the four premolars (p 1-4) are commonly retained longer than in the fiercer species of the northern lati- tudes. In these the second lower premolar is soon lost. The first true molar, m i, has a longer and narrower crown than the one above. The second true molar, m 2, has a narrow, oblong, subquadrate, tubercular crown, which, like that of the first true molar, is supported by two fangs. The crown of the third lower molar, m 3, is contracted posteriorly, and supported by two con- nate fangs ; it is relatively smallest in the Sun-bears, and largest in the great Ursus spelceus. The dental formula of the genus Ursus is 4 V m si = 42 (fig< 293 ' "' Ursus ^ It is essentially the same both in number and kind of teeth as in the genus Canis, but the individual or specific varieties, which in the Dog affect the true molar teeth, are confined in the Bears to the premo- lars. It would seem in the genus Ursus as if the preponde- rating size of the * Iff ; c \\ ' 263 large tubercular true molars had tended to blight o the development of the premolars. In fig. 263 the deciduous teeth and their successors are riveil aS disiollVed Deciduous dentition, Bear (Ursus). by the removal of the outer wall of their sockets. The milk- molars, four in number on each side of both jaws, progres- sively increase from the first to the fourth. The character- istic relative position to them of the premolars is shown at p 2, 3, and 4. Behind these is shown the large formative cell of the first, m i, of the true molar series. 336 ANATOMY OF VERTEBRATES. 264 22 Dentition of Seal (Phoca). A tendency to deviate from the ferine number of the incisors is seen in the most aquatic and piscivorous of the Musteline quadrupeds, viz., the Sea-otter (JEnhydra), in which species the two middle incisors of the lower jaw are not developed in the permanent dentition. In the family of true Seals the incisive formula is further reduced, in some species even to zero in the lower jaw, and it never exceeds f :- . All the PhocidcE possess powerful canines ; only in the aberrant Walrus, fig. 265, are they absent in the lower jaw, but this is compensated by the singular excess of development which they manifest in the upper jaw. The molar series, fig. 264, m, usually includes five, rarely six, teeth on each side of the upper jaw, and five on each side of the lower jaw ; with crowns which vary little in size or form in the same individual. They are supported in some genera, as the Eared Seals ( Otarice) and Elephant Seals ( Cystophord), by a single fang ; in other genera by two fangs, which are usually connate in the first or second teeth ; the fang or fangs of both incisors, canines, and molars, are always remarkable for their thickness, which commonly surpasses the longest diameter of the crown. The crowns are most commonly compressed, conical, more or less pointed, with the ( cingulum ' and the anterior and posterior basal tubercles more or less developed ; in a few of the largest species they are simple and obtuse, and particularly so in the Walrus, in which the molar teeth are reduced to a smaller number than in the true Seals. In these the line of demarcation between the true and false molars is very indefinitely indicated by characters of form or position ; but, according to the instances in which a deciduous dentition has been observed, the first three permanent molars in both jaws succeed and displace the same number of milk-molars, and are consequently, ' premolars ; ' occa- sionally, in the seals with two-rooted molars, the more simple character of the premolar teeth is manifested by their fangs being- connate, and in the Stenorhy nchus serridens the more complex character of the true molars is manifested in the crown. There is no special modification of the crown of any tooth by which it can merit the name of a ( sectorial ' or f carnassial ; ' but we may point with certainty to the third inolar above and the fourth TEETH OF DIPHYODONTS. 337 below, as answering to those teeth which manifest the sectorial character in the terrestrial Carnivora. The coadaptation of the crowns of the upper and lower teeth is completely alternate, the lower tooth always passing into the interspace anterior to its fellow in the upper jaw. In the genus Plioca proper (Calocephalus, Cuv.) typified by the common seal (Ph. vitulina), the dental formula is . 3.3 m 1.1 4.4 1.1 The Sterrincks with double-rooted molars (Pelagius, Steno- rhynchus} have four incisors above as well as below, i. e. J- :f . In the Saw-tooth Sterrinck (Stenorhynchus serridens), the three anterior molars on each side of both jaws are four-lobed, there being one anterior and two posterior accessory lobes ; the remaining posterior molars (true molars) are five-lobed, the principal cusp having one small lobe in front, and three de- veloped from its posterior margin ; the summits of the lobes are obtuse, and the posterior ones are recurved like the principal lobe. The allied sub-genus (Ontmatophoca) of Seals of the southern hemisphere has six molar teeth on each side of the upper, and five on each side of the lower jaw, with the principal lobe of the crown more incurved. In the genus Otaria the dental formula is- .3.3 1.1 4.4 2.2 Z - I C - \ p 1 Til ~ - = GO. 22 1144 1.1 The two middle incisors are small, sub-compressed, with the crown transversely notched; the simple crowns of the four incisors below fit into these notches ; the outer incisors above are much larger, with a long-pointed conical crown, like a small canine. The true canine is twice as large as the adjoining in- cisor, and is rather less recurved. The molars have each a single fang. In Stemmatopus the last upper molar has two divergent fangs, at least in the young state. In the great proboscidian and hooded Seals (Cystophora), the incisors and canines still more predominate in size over the molars ; but the incisors are reduced in number, the formula here s .2.2 1.1 4.4 1.1 The molars are single-rooted, and the incisors laniariform. The two middle incisors above and the two below are nearly equal ; 1 cxxm". p. 38. VOL. III. Z 333 ANATOMY OF VEETEBRATES. 265 the outer incisors above arc larger. The canines are still more formidable, especially in the males ; the curved root is thick and subquadrate. The crowns of the molar teeth are short, sub-com- pressed, obtuse ; sometimes terminated by a knob and defined by a constriction or neck from the fang ; the last is the smallest. In the Walrus (Trichcchus rosmarus, fig. 265) the normal incisive formula is transitorily represented in the very young animal, which has three teeth in each premaxillary and two on each side of the fore-part of the lower jaw ; they soon disappear, except the outer pair above, which remain close to the maxillary suture, on the inner side of the sockets of the enormous canines, and seem to commence the series of small and simple molars which they resemble in size and form. In the adult there are usually three such molars on each side, behind the permanent incisor, and four similar teeth on each side of the lower jaw ; the anterior one passing into the interspace between the upper incisor and the first molar. The crowns of these teeth must be almost on a level with the gum in skim and Teeth of the recent head ; they are very obtuse, and worn obliquely from above down to the inner border of their base. The molars of the lower jaw are rather narrower from side to side than those above, and are convex or worn upon their outer side. Each molar has a short, thick, simple and solid root. The upper canines are of enormous size, descending and pro- jecting from the mouth,, like tusks, fig. 265, c, slightly inclined outward and bent backward ; they present an oval transverse section, with a shallow longitudinal groove alon; the inner side, o O O and one or two narrower longitudinal impressions upon the outer side ; the base of the canine is widely open, its growth being uninterrupted. Their homotype below retains the size and shape of the succeeding molars. The food of the Walrus consists of sea-weed and bivalves ; the molars are well adapted to break and crush shells ; and frag- ments of a species of Mi/a have been found, with pounded sea- weed, in the stomach. The canine tusks serve as weapons of offence and defence, and to aid the animal in mounting and clambering over blocks of ice. TEETH OF PIPHYODONTS. 339 A large extinct carnivorous animal (Machairodus, fig. 293, vi.), had the upper canine teeth, c, developed to almost the same dis- proportionate length as in the Walrus, whereby they were also compelled to pass outside the lower jaw when the mouth was shut. But these teeth were shaped after the type of the feline canines, only with more compressed and trenchant crowns ; and they were associated with other teeth in number and kind demonstrating the feline affinity of the genus Machairodus. Its remains occur in newer tertiary deposits and in caves. 1 In older tertiary formations, remains of carnivorous Mammals have been found with the three true molar teeth as expressly modified for the division of flesh, and as worthy the term of ( sectorials ' as the teeth so called in the lion. These teeth were associated with conical premolars, long canines, and short incisors, so as to exemplify the typical formula, e.g. .3.3 1.1 4.4 3.3 Z 3T3 ;C LT ;/J 474 ;m 3.3 = 44 - The extinct Hy&nodon and Pterodon of the upper eocene forma- tions of Hampshire and of France, manifest this interesting and instructive character of dentition. .A reduced view of the lower jaw of the Hy&nodon Rcquieni is given in fig. 266. After the canines, c, come four successively enlarging conical com- pressed premolars, p 14; then, instead of 266 Dciititioii, lower jaw, of Hycenodon. a single carnassial re- presenting the first true molar, there are three of these singu- larly modified teeth- the first, m i, being of suddenly small size, as compared with the antecedent premolar, and obviously illustra- ting; its true nature as a continuation of the deciduous series, with C3 which, doubtless, it agreed in size. It became a permanent tooth only because there was no premolar developed beneath it, so as to displace it. The succeeding carnassial true molars, m 2 and 3, progressively increase in size. The symbols in fig. 266 denote the homolooies of the teeth. The marks of abrasion on the lower o teeth in the Hy&nodon prove the upper series to have been the same in number. A second form of equally ancient Carnivore was a mixed- 1 Kent's Hole, Devonshire, e. g.; cxvi". p. 174. Z 2 340 ANATOMY OF VERTEBRATES. feeding animal, allied to the viverrine and canine families, the true molars presenting the tuberculate modification, and the typical number and kinds of teeth being functionally developed, as in the Hycenodon. The series in the upper jaw are shown in fig. 267. The term f tubercular ' is as applicable to the three true molars of the Amphicyon, m i, 2, 3, as the term ' carnassial ' is to those of the Hycenodon. 267 Dentition, upper jaw, Amphicyon. 221. Teeth of Ungulata.- - The most common characteristic of this dentition is the large size, cuboid shape, and complex structure of the crowns of the grinding teeth. The enamel not only incloses but dips or penetrates into the substance of the dentinal body, and the cement, which is thick, accompanies the enamel. Thus the massive grinding organ is made up of substances of different densities, and the working surface is irregular by the projections of the harder material, as in the mineral ( grit ' that is thereby suitable as a millstone. A. Homologies of the parts of the grinding surface.- -The pattern of the grinding surface, especially of the upper molars, varies in each genus of Ungulata, and is eminently characteristic thereof. Nevertheless, two leading types may be recognised. One, of un- symmetrical character, was early shown in Palceotherium , and is traceable in secondary modifications characteristic of Paloplothe- rium, Hipparion, Equus, Hyrax, and Rhinoceros. A second was as early manifested in Anoplotherium and Dichodon ; it is more symmetrical in pattern, and is traceable, with modifications, in Dicotyles, Sus, Hippopotamus, and Ruminants. Indications of a more generalised type of molar have been obtained from tertiary TEETH OF TJNGULATA. 341 deposits antecedent in time to those characterised by Palceo- or Anoplo-therium : they are afforded by Pliolophus, 1 and Coryplwdon* The answerable parts of the grinding surface will first be illustrated in the unsymmetrical series. In Palaotherium, e. g. fig. 268, the tract of dentine, a, b, extending along the outer side of the crown, has two indents, /, /, whereby it is divided into two lobes, an anterior or * ant-external lobe,' , and a posterior or f post-external lobe,' b. The tract of dentine along the inner side of the crown is also divided by two deeper and more oblique clefts or valleys into an ' ant-internal lobe,' c, m, and a e post-internal lobe,' d : these lobes extend obliquely inward and backward from the outer ones, of which they are direct con- 268 269 Fpper molar (m 2) : Palceotherium magnum. Upper molar (m 2) : Paloplotherium. tinuations. The anterior of the two inner clefts, e, i, extends from the middle of the inner surface of the crown obliquely out- ward and forward : the posterior one, g, h, enters at the posterior side of the crown, and extends nearly parallel with e, i: both valleys expand and deepen at their blind ends. At an early period of the attrition of the crown they intercommunicate, and extend to the anterior side of the crown, at Z, as in the younger molar of Palop /other ium, fig. 269. But the shallow communica- ting passages between *li and z, i and /, are soon obliterated, the dentine of lobe d becoming continuous with b ; and that marked e with a. In Paloplotherium a branch valley, also, extends from e z, to the anterior side of the crown, &, cutting off the part of the ant-internal lobe m from the rest of c ; but, by con- tinued abrasion, this valley is also obliterated, and the tooth assumes more of the palaeotherian pattern. In Equus, fig. 270, the valleys are of less equal depth than in Palceotherium, and are 1 cxv". p. 54. 2 cxvi". p. 299. 342 ANATOMY OF VERTEBRATES. so shallow midway that, at an early stage of attrition, the entry of the posterior valley, g, is separated from its termination, h ; and that of the internal valley, e, from its termination i ; the blind ends of both valleys, moreover, are more extended and irregular, than in Pal&otherium, with the tendency to curve, so as to produce the crescentic form of the islands, z, h, in fig. 270. The oblitera- tion of the mid-part of the accessory valley, A, unites the dentinal tract, m } to the rest of the lobe, c, as in PalcBotherium, fig. 268 : but it long remains separate in Jfipparion, as in Paloplotherium , fig. 269. The Rhinoceros and Hyrax more closely adhere to the Palreo- therium type : but the outer indents, f, f, are less marked. The 270 271 Upper molar (m 2), Equus caballus. Upper molar (?;; 2). Ncgaceros. horse approaches nearest to the symmetrical type of the Rumi- nants, in which the homologous parts of the crown can, mostly, be well defined. In the unworn crown of the Ruminant molar, fig. 271, the valley, g, h, extends across the crown more parallel with the long axis of the jaw, than in fig. 268, curving with the concavity outward : it communicates with the valley, i ; and, as in Paloplo- therium, this is continued to the foreside of the crown, as at /, fig. 269, severing the lobe c from a. In Ruminants, both the O C? . * anterior and posterior entries to this antero-posterior double- curved cleft are so shallow that they are soon obliterated, and the lobe b is continued by a tract of dentine, with d, along the hind part of the crown : as the lobe a is continued into lobe c at the fore part, as seen in the worn molar of the deer, fig. 271 : the middle of valley, e, is separated from the end i, as in the horse : but the course of this valley is more transverse, and more di- rectly bisects the antero-posterior valley, h, i : thus the inner lobes c and d are more parallel with and similar to the outer TEETH OF UNO UL AT A. 343 extends straight across the tooth to 2:2 Upper molar (m 2\ Hippopotamus lobes #, b. Whether the accessory lobule m, be a homologue of the end, so marked, of lobe c in PalceotJiermm, Paloplotherium, and Equus, or a special development at the entry of valley e may be doubtful. In the Hippopotamus, fig. 272, the valley commencing at the inner side of the crown at e ?i, bisecting the crown trans- versely : it is also bisected, antero-posteriorly, by a shal- lower valley, answering to h, i, fig. 271. At the stage of attrition shown in fig. 272, the remnant of the latter valley is seen at h and i : the deeper transverse valley, e, n, remains : the shorter indents,/,/, g, k, give the trefoil character to the two chief divisions of the crown characteristic of Hippopotamus. Another exposition of the homologous parts of the complex crowns of the Unsfulate molars assumes the crucial division into O four quarters or lobes to be the primitive modification. The fore- and-aft cleft has already begun to be filled by the mid-lobules in Pliolophus : the arrest of the outer end of the transverse cleft produces the continuity of a with b : that of its mid-part, of d with e : the obliteration of both ends of the antero-posterior cleft insulates that cleft, as in the Ruminant. The obliteration of the middle of the transverse cleft produces the continuation of a, b, with d, c ; while the oblique continuation of e with i, and the retention of the continuity of y with h, leads to the type of Palceotherium and Rhinoceros. A sub-type of grinding surface is produced by the existence of a transverse without an antero-posterior valley, dividing the crown into a pair of transverse ridges ; as in the Tapir ; which, however, is mainly the greater development, and more transverse disposition, of the tracts b, d, and a, c, in Palceotherium, fig. 268. The bilophodont ' sub-type becomes more marked in Dinothcrium, fio-. 288, and in the anterior small molar of Mastodon : the sue- O J cessive multiplication of the transverse ridges completes the transition into the molar character of Elcphas. B. Artiodactyla. The extinct Cheer opotamus, Anthrac other him, Hyopotamus and Hippoliyus^ had the typical dental formula, and this is preserved in the existing representative of the same section 344 ANATOMY OF VERTEBRATES. of non-ruminant Artiodactyles, the Hog. The permanent dental formula of the genus Sus is illustrated in fig. 273. The upper incisors decrease in size from the first, i i, to the third, i 3, receding from each other in the same degree ; the first is relatively larger in the Sus larvatus than in the Sus scrofa ; the 273 Dentition of Boar (Sus). basal line of the enamel is irregular ; that substance extends more than an inch upon the outer side of the tooth, but only two or three lines on the inner side. The lower incisors are long, sub- compressed, nearly straight ; the second is rather larger than the first ; the third is the smallest, as in the upper jaw. The upper canines, in the Wild Boar, fig. 273, c, curve" forward, outward, and upward ; their sockets inclining in the same direc- tion, and being strengthened above by a ridge of bone, which is extraordinarily developed in the Masked Boar of Africa. The enamel covering the convex inferior side of this tusk is longi- tudinally ribbed, but is not limited to that part ; a narrow strip of the same hard substance is laid upon the anterior part, and another upon the posterior concave angle forming the point of the tusk, which is worn obliquely upwards from before, and backwards from that point. In the Sow the canines are much smaller than in the Boar. Castration arrests the development of the tusks in the male. The teeth of the molar series progressively increase in size from the first to the last. The first premolar, ib. p \ , has a simple, compressed, conical crown, thickest behind, and has two fangs. The second, p 2, has a broader crown with a hind-lobe, TEETH OF UNGULATA. 345 having a depression on its inner surface, and each fang begins to be subdivided. The third, p 3, has a similar but broader crown implanted by four fangs. The fourth, p 4, has two principal tubercles and some irregular vertical pits on the inner half of the crown. The first true molar, m i, when the permanent dentition is completed, exhibits the effects of its early development in a more marked degree than in most other mammals, and in the Wild Boar has its tubercles worn down, and a smooth field of dentine exposed by the time the last molar has come into place ; it originally bears four primary cones, with smaller subdivisions formed by the wrinkled enamel, and an anterior and posterior ridge. The four cones produced by the crucial impression, of which the transverse part is the deepest, are repeated on the second true molar m 2, with more complex shallow divisions, and a larger tuberculate posterior ridge. The greater extent of the last molar, m 3, is chiefly produced by the development of the back ridge into a cluster of tubercles ; the four primary cones beinsf distinguishable on the anterior 2 1 4 main body of the tooth. The crowns of the lower molars are very similar to those above but are rather nar- rower, and the outer and inner basal tubercles are much smaller, or are wanting ; the grinding surface of the i i r> 0*7/1 Grinding surface, (TO 3) fite. last is shown in ng. 2/4. The first or deciduous dentition of the Hog consists of The canines are feeble, and have their normal direction in both jaws, the upper ones descending according to the general type, which is not departed from until at a later period of life. The first deciduous molar is not succeeded by a premolar, but holds the place of such some time after the other deciduous molars are shed. The dentition of the Wart-hogs is reduced by the suppression of certain incisors and of the first two premolars the tooth- forming energy being, as it were, transferred to the last true molar, fig. 275, m 3, wiiich is even more remarkable than in the common hog for its size and complexity in both jaws : it is per- haps the most peculiar and complex tooth in the whole class of Mammalia. The surface of the crown presents three series of enamel-islands, in the direction of the long axis of the grinding surface ; the eight or nine islands of the middle row are elliptic and simple ; those of the other rows are equal in number, but are 346 ANATOMY OF VERTEBRATES. sometimes subdivided into smaller islands. These islands or lobes are the abraded ends of long and slender columns of dentine, encased by thick enamel, and the whole blended into a coherent crown by abundant cement, which fills up all the interspaces, and forms a thick exterior investment of the entire complex tooth. The milk-molars are J :f- in number ; but only the two last are succeeded by premolars. These are small, and, after the wearing out of the first true molar, are shed, leaving the remnant of the second true molar, fig. 275, in 2, with the last large one, m 3, to which the work of mastication is confined in old Wart-hogs. This interesting modification, as to order and number, in the 276 Deutition, lower jaw, old Wart-hog (Phacochoerus). Dentition of Hippopotamus. change of the dentition, has thrown important light on the more ano- malous dentition of the Elephant. 1 The tendency to excessive development which characterises the canine teeth in the Suidce, affects both these and the incisors in the genus Hippopotamus. The two median inferior incisive tusks, fig. 276, z, are cylindrical, of great size and length ; the two outer incisors are likewise cylindrical and straight, but much smaller. The upper canines curve downward and outward ; their exposed partis very short, and is worn obliquely at the forepart; they are three-sided, with a wide and deep longitudinal groove behind. The lower canines, ib. c, are massive, curved in the arc of a circle, subtriedral, the angle rounded off between the two an- terior sides, which are convex and thickly enamelled, the posterior side of the crown being almost wholly occupied by the oblique abraded surface opposed to that on the upper canine. The im- planted base of each of these incisive and canine teeth is simple, and excavated for a large persistent matrix, contributing to their perennial growth by constantly reproducing the dental matter to 1 CLXXiii". p. 495. TEETH OF UNGULATA. 347 replace the abraded extremities. The direction of the abraded surface is in part provided for by the partial disposition of the enamel. The molar series consists of 4.4 3^ The first premolar is small, far in advance of the second, and is soon shed: the others (fig. 276, 2, 3, 4) form a continuous series with the true molars (m, 2, 3). These have the double trefoil character shown in fig. 272. The crown of the last, in the lower jaw, is lengthened by a fifth cusp developed behind the normal pairs. The large tusks, fig. 276, c, exhibit the maximum of density in their component tissues. The enamel ( strikes fire ' with steel like flint. The compact dentine has a high commercial value, especially for the fabrication of artificial teeth. It differs from true ivory by showing, in transverse section, the simple concentric instead of the ( engine-turned' or curvilinear decussating lines. 1 The affinities of the Hippopotamus are clearly manifested by the character of its deciduous dentition ; and if this be compared with the dentition at a like immature period in other Unguhita, it will be seen, by its closer correspondence with that of Artio- dactyles, and more especially the Phacochere, that the Hippo- potamus is essentially a gigantic Hog. The formula of the teeth which are shed and replaced, is .2.2 1.1 3.3 If the small and simple tooth, which is developed anterior to the deciduous molars, and which has no successor, be regarded, from its early loss in the existing Hippopotamus, as the first of the deciduous series, we must then reckon with Cuvier four milk- molars on each side of both jaws. The incisors in both jaws are simply conical and subequal, with an entire cap of enamel on the crown. The deciduous canines scarcely surpass them in size in the upper jaw, and not at all in the lower. Projecting forward, here, from the angles of the broad and straight syniphysis, they appear like an additional pair of incisors ; and this character of equality of development was retained by the ancient form of Hippopotamus with the more typical number of incisors, -|:-J , which formerly inhabited India. The first true deciduous molar, d 2, has a conical crown and two fangs in both jaws. That above has also a conical crown with one strong posterior and two anterior ridges. The second 1 In v. is described (p. 509) and figured (pi. 142), the lower tusk of a Hippopota- mus which, after fracture, had been united again by a mass of ' ostcodentine.' 348 ANATOMY OF VERTEBRATES. deciduous molar, ds, has a large trilobate crown, the first lobe small, with an anterior basal ridge ; the second large, conical, with three longitudinal indentations ; the third lobe still larger, and cleft into two half-cones by an antero-posterior fissure assuming the normal pattern of the true molars. The third deciduous molar, d 4, above more closely resembles the ordinary upper true molar ; but its second pair of demi-cones are relatively larger. In the lower jaw the last deciduous molar, d 4, has a more complex crown than that of any other teeth of the permanent or deciduous dentition. It has three pairs of demi-cones, progressively increasing in size, from before backward, with an anterior and posterior basal ridge and tubercles. Like the last trilobate deciduous lower molar of the Hog, it increases in thickness posteriorly, instead of diminishing here, like the last true molar of the lower jaw of the adult Hippo- potamus. The upper incisors, and the first premolar of both jaws, are not developed in the typical Ruminants, rarely the upper canines : the dental formula being : 27 i ^2 ; c . p !?. TO H = 32 (vol. ii- P- 474, fig. 324). The gazelle, the sheep, the ox respectively representing the families Antilopidce, Ovidce, and Bovida, which are collectively designated the ' hollow-horned ruminants ' - all present this formula. It likewise characterises many of the solid-horned ruminants, or the deer tribe ( CerrzW<),the exceptions hav- ing canine teeth in the upper jaw of the male sex, and sometimes also in the females, though they are always smaller in these. The upper canines attain their greatest length in the Muntjac (vol. ii. p. 478, fig. 328, a a) and the small Musk- deer, and especially in the typical species (Moschns moschiferus, fig. 277.) These teeth, in- deed, in the male Musk, ib. c, present proportions intermediate be- tween those of the upper canines of the Machairodus and of the Morse. The inverse relationship in the development of teeth and horns, exemplified by the total absence of canines in the Rumi- nants with persistent frontal weapons, by their first appearance 1 The line traverses the Cuvierian ' dents carnassieres ' ; the interrupted line tra- verses the Blainvillian * dents principales '. Dentition, Moschus moschiferus.i TEETH OF UNGULATA. 349 278 Dentition of Camel (Camehta boctrianus) . in the periodically hornless deer, and by their larger size in the absolutely hornless Musks, is further illustrated by the presence not only of canines, but of a pair of laniariform incisors, fig. 278, i, in the upper jaw of the Camelidce. In the Camel and Dromedary the upper canines, fig. 278, c, are formidable for their size and shape, but do not project beyond the lips like the tusks of the Musk-deer ; they are more feeble in the Lla- mas and Vicugnas, and are always of smaller size in the females than in the males. The inferior ca- nines, 0, moreover, retain their laniariform shape in the Camelidce, and are more erect in position than in the ordinary Ru- minants. They are separated by a short diastema from the inci- sors in the Auchenice. The true nature of the corresponding canines in the ordinary Ruminants, in which they are procumbent, and form part of the same series with the incisors, is always indicated by the lateness of their development, and often by some peculiarity of form. Thus in the Moschus, fig. 277, c, they are smaller and more pointed than the incisors ; in the Giraffe they have a much larger crown, which is bilobed. The laniariform tooth in the premaxillary bone of the Camelidce, fig. 278, i, which represents the upper and outer incisor, 2, is smaller than the true canine, c, which is placed behind it in the Camel and Dromedary ; but in the Vicugna it is as large as, or larger than, the true canine. Most of the deciduous molars of the Ruminants resemble in form the true molars ; the last milk-molar, for example, fig. 279, d 4, in the lower jaw, has three lobes like the last lower true molar, m 3. The deciduous molars in existing true Ruminants are , . , i n Deciduous arid permanent teeth of a Sheep. three in number on each side, and, being succeeded by as many premolars, the ordinary perma- nent molar formula is 3.3 3.3 279 d c 3 'II 350 ANATOMY OF VERTEBRATES. but there is a rudiment of d \ in the embryo Fallow-deer, and in one of the most ancient of the extinct Ruminants (Dorcatherium, Kaup) the normal number of premolars was fully developed. The characteristic complexity of the Ruminant grinder, fig. 271, is seen, in the permanent series, only in the three posterior teeth of both upper and lower jaws, which are the true molars ; the three first, or premolars, having more simple crowns than those which they displace. The complexity in question is the result of peculiar plications of the formative capsule, some of which are longitudinal, or project inward from the sides of the capsule, and form peninsular folds of enamel upon the grinding surface of the tooth, whilst others depend vertically from the summit of the matrix into the body of the tooth, and form islands of enamel when the crown begins to be worn. Of the longi- tudinal folds, two in the upper true molars are external, broad, but shallow, and often sinuous, and one is internal, narrow, and deep, extending quite across the summit of the crown of the tooth, and decreasing in depth toward the base of the crown. The corresponding fold of enamel in the completed tooth, ac- cordingly, extends more or less across the crown, from within outward, as the tooth is less or more worn. The whole circum- ference of this complex molar is also invested by a coat of enamel and a thinner layer of cement. In some Ruminants, e.g. Ox, Deer, and Giraffe, a small vertical column, fig. 271, m } is de- veloped at the internal interspace of the two lobes of one or more of the upper true molars, varying in height, and rarely reaching the summit of the new-formed crown, but longest in the Bovidce. Different genera of Ruminants also differ in the depth and sinu- osity of the two outer longitudinal folds, f y and in the depth and complexity of the two vertical folds, h,i, which likewise are united in some species by a longer common base than in others, producing thereby a continuity of the enamel, and complete antero-posterior bisection of the grinding surface during a longer period of attri- O ~ O O A tion. The molars of the Camel present the most simple con- dition of the Ruminant type of these teeth ; the transverse fold dividing the crown being short, the dentine of the two lobes soon C3 O forms a continuous tract. The common base of the crescentic vertical folds of the capsule being likewise short, the enamel islands are soon separated from each other. They include a shallow or narrow crescentic cavity, with a simple but slightly sinuous contour. The two outer shallow longitudinal depressions of the crown have no middle rising ; and there is no columnar process at the interspace of the tAvo inner convexities. TEETH OF UNGULATA. 351 The lower molars are like the upper ones reversed. The single median longitudinal fold is external, and divides the convex outer sides of the two lobes. The base of the fold extends, in some species, across the molar for some distance before it contracts in breadth, retreating toward the outer side, and the two lobes of the crown accordingly continue to be completely divided for a longer period, as in the Elk and Giraffe. The inner surface of the molar is gently sinuous, the concavities being rarely so deep as those of the outer surface of the upper molars. The lower molars are always thinner, in proportion to their breadth, than those above, and the crescentic islands are narrower and less bowed. The differences which the lower molars present in dif- ferent genera of Ruminants are analogous to those in the upper molars, but are less marked. The accessory small column, when present, as in Bos, Urus, Megaceros, and Alces, is situated at the outer interspace of the convex lobes, and nearer the base in the Cervidce than in the Bovidce. It is not developed in the Antelopes, Sheep, or Camel, and is wanting in most of the smaller species of Deer. The last true molar of the lower jaw is characterised in all Ruminants by the addition of a third pos- terior lobe. This is very small and simple in the Camel and the Gnu, is relatively larger in the Bovidce and Cervidce, and pre- sents, in the Megaceros and Sivatherium, a deeper central enamel island or fold, which also characterises the smaller third lobe in the Giraffe. The lower molars of the genus Auchenia are pecu- liarly distinguished by the vertical ridge at the forepart of the anterior lobe, which does not exist in the Camels of the Old World. In all Ruminants, the outer contour of the entire molar series is slightly zigzag, the anterior and outer angle of one tooth pro- jecting beyond the posterior and outer angle of the next in advance. All the three lower premolars have compressed, sub- trenchant, and pointed crowns in the small Musk-deer ( Trayulus). The true Musk (Moschus) more resembles the ordinary Deer in its premolars. The aberrant Camelidcz deviate most from ruminant type in the position, shape, and number of the pre- molars: the anterior one, fig. 278, s, is laniariform in both jaws. As phenomena of dentition serve to determine, or indicate, the age of Hoofed beasts, a table is subjoined in which the charac- teristic teeth are indicated by the symbols adopted in my ( Odon- tography' (v), and illustrated in figs. 279 and 294, with reference to those domesticated varieties raised for food, which are usually exhibited, in competition, of prescribed ages, at the great cattle 352 ANATOMY OF VERTEBRATES. shows. The range of variety, for which allowance may be made, is noted in the Ox and Sheep. TABLE OF THE TIMES OF APPEARANCE OF THE PERMANENT TEETH IN THE Ox, SHEEP, AND HOG. Symbols. OX. SHEEP. HOG. Early. Year. Month. Late. Year. Mouth. Early. Year. Month Late. Year. Month. Year. Month. i 1 1 9 2 3 1 1 4 to 8 1 i2 2 3 2 9 1 6 2 to 4 1 6 i 3 2 9 3 3 2 3 2 9 to 12 9 c 3 3 3 9 3 3 6 9 ml 4 6 3 6 6 m2 1 3 1 8 9 1 10 m3 2 2 3 1 6 2 1 6 dorp 1 p2 pZ p 4 2 6 2 6 2 8 2 8 2 8 3 2 2 2 3 2 6 2 6 2 6 6 1 1 1 3 C, Perissodactyla.- -The Horse is selected as the first example of the dentition of the hoofed Quadrupeds with toes in uneven number, because it offers in this part of its organisation some transitional 280 Dentition of Horse (Equus). features between those of the dental characters of the typical members of the artiodactyle and of those of the perissodactyle Ungulata. All the kinds of teeth are retained, in nearly normal numbers, in both jaws, and with almost as little unequal or excessive de- velopment as in the Anoplothere ; but the pi-olongation of the slender jaws carries the canines, figs. 280, c, and incisors, ib. i y to TEETH OF UNGULATA. 3,53 281 some distance from the molars, and creates a long diastema, as in the Ruminants and Tapirs. The first deciduous molar is very minute and is not succeeded by a premolar; yet, remaining longer in place than the larger deciduous molars behind, it represents the first premolar, and completes the typical number of that division of the grinding series. If the dental formula of the genus Equus be restricted to the functionally developed perma- nent teeth, it will be- .3.3 1.1 3.3 3.3 The outer side of the upper molar of the Horse (Equus Ca- ballus, fig. 269) is impressed, as in the Pala3othere, fig. 267, by two wide longitudinal channels : the other evidences of the peris- sodactyle type of grinding surface, and the modifications thereof, are given at p. 341. In the lower jaw, the teeth, as usual, are narrower transversely than in the upper jaw ; they are divided externally into two convex lobes by a median longitudinal fissure, and on the inner side they present three principal unequal con- vex ridges, and an anterior and posterior narrower ridge ; but the crown of the molar is penetrated from the inner side by deeper and more complex folds than in the Rhinoceros or Palaeothere. The incisors, figs. 280, 285, i, are arranged close together in the arc of a circle at the ex- tremity of both jaws. They are slightly curved, longitudinally grooved, with long simple subtri- hedral fangs tapering to their extremity, fig. 280. The crowns are broad, thick, and short. The contour of the biting surface, before it is much worn, approaches an ellipse. These teeth, if found detached, recent or fossil, are distin- guishable from those of the Ruminants by their greater curvature, and from those of all ~ * other animals by the fold of enamel (ib. c'), which penetrates the body of the crown from its broad flat summit, like the inverted finger of a glove. When the tooth begins to be worn, the fold forms an island of enamel inclosing Section of incisor Horse - a cavity, s, partly filled by cement and partly by the discoloured substances of the food ; this is called by horse-dealers the ' mark.' In aged horses the incisors are worn down below the extent of the fold, and the mark disappears. The cavity is usually obli- terated in the first or mid-incisors at the sixth year, in the second VOL. nr. A. A 854 ANATOMY OF VERTEBRATES. incisors at the seventh year, and in the third or outer incisors at the eighth year, in the lower jaw. It remains longer in those of the upper jaw, and in both the place of the ( mark ' continues for some years to be indicated by the dark-coloured cement or osteo-dentine. The canines are small in the stallion, less in the gelding, and rudimental in the mare. The unworn crown is remarkable for the folding in of the anterior ami posterior margins of enamel, which here includes an extremely thin layer of dentine. The upper canine is situated in the middle of the long interspace be- tween the incisors and molars : the lower canine, fig. 280, c, is close to the outer incisor, as in the Ruminants, but is better dis- tinguished by its cuspidate form. The most obvious character by which the horse's molars may be distinguished from the complex teeth of other Herbivora cor- responding with them in size, is the great length of the tooth before it divides into fangs. This division, indeed, does not begin to take place until much of the crown has been worn away; and thus, except in old horses, a considerable portion of the whole of the molar is implanted in the socket by an undivided base. This is slightly curved in the upper molars. It provides for mas- tication during a longer life than in the cow. The following is the average course of development and suc- cession of the teeth in the Equus Caballus :- -The summits of the first functional deciduous molar 1 ( 6 first grinder' of veterinary \ o authors) are usually apparent at birth; the succeeding grinder 2 sometimes rises a day or two later, sometimes together with the first. Their appearance is speedily followed by that of the first decidu- ous incisor, fig. 282, d i ( ( centre nipper ' of veterinarians), which usu- ally cuts the gum between the third and sixth days ; but occasionally pro- trudes at birth. The second deciduous incisor, ib. d 2, appears between the twentieth and fortieth days, and about this time the rudimental molar, 3 comes into place, and the last de- ciduous molar 4 begins to cut the gum. Deciduous iiuMsor 8kl Cult. Lower jaw. IncNive dentitinji of 4-year old Colt. Lower ja\v. molar, m i, appears between the eleventh and fourteenth months. The f second ' molar, m 2, follows at the twentieth month or the second year. The first functional premolar, p 2, displaces the deci- duous molar, d 2, at from two years to two years and a half old. 1 The first permanent incisor, fig. 283, i i, displaces d 3, and pro- trudes from the gum at between two years and a half and three years. At the same period the second or penultimate premolar, p 3, pushes out the penultimate milk-molar,, and the penultimate true molar, m 2, comes into place. The last premolar, p 4, displaces the last deciduous molar at between three years and a half and four years; the appearance above the gum of the last true molar, m 3, is usually somewhat earlier. The second incisor, fig. 284, i 2, pushes out its deciduous predecessor at about three years and eight months. The permanent canine or ' tusk,' c, next follows ; its appearance indicates the age of four years and a half; but it sometimes comes earlier. The third, or outer incisor, fig. 285, i 3, pushes out the de- ciduous incisor, d 3, about the fifth year, but is seldom in full place before the horse is five years and a half old ; the last premolar is then usually on a level with the other grinders. Upon the rising 1 The homologous teeth in the young Hyrax, fig. 287, are indicated by the same symbols, and the sole developmental difference from the Horse is the displacement r-\ d ] by up 1 of functional size. A A 2 356 ANATOMY OF VERTEBRATES. of the third permanent incisor, or ( corner nipper,' the ( colt ' be- comes a ' horse,' and the ' filly ' a ' mare,' in the language of the horse-dealers; after the disappearance of the 'mark 'in the in- cisors, at the eighth or ninth year, the horse becomes ( aged.' The modifications which the upper molars of Hi/rax, fig. 286, present, as compared with those of Paleotherium, will be readily understood by the re- 3 marks in the section on the homologies of the grinding sur- face, as illustrated by figs. 268- 2 70. The present genus is a mi- niature form of the family, and, like the primitive eo- and mio- therium), retains large incisors, with a type molar series, e.g. Incisive dentition, 5-year old Horse. Lower jaw. . 1.1 o.o 4.4 \m'- - = 32. Dentition, upper jaw (Hyrax). There are no canines. As to the incisors in Hyrax or Rhinoceros the species vary, not only in regard to their form and proportions, 286 but also their existence ; and in the varieties of these teeth we may dis- cern the same inverse relation to the develop- ment of the horns which is manifested by the ca- nines of the Ruminants. Thus, the two-horned Rhinoceroses of Africa, which are remarkable for the great length of one (Rh. bicornis, Rh. simus) or both (Rh. Keitloa) of the nasal weapons, have no incisors in their adult dentition; neither had that great extinct two-horned species (Rh. tichorinus), the prodigious development of whose horns is indicated by the singu- lar modifications of the vomerine, nasal, and premaxillary bones, in relation to the firm support of those weapons. The Sumatran. bicorn Rhinoceros combines, with comparatively small horns, moderately developed incisors in both jaws. The incisors are of larger size in the unicorn Rhinoceroses (Rh. Indicus and Rh. Son- daicus) ; still larger, relatively, in the hornless Acerotherium and Hyrax, figs. 286, 287, i. TEETH OF UNGULATA. 357 The deciduous molars of the Rhinoceros are, in number as well as in shape, similar to those in Hyrax, which bears the same re- lation to the great Rhinoceros as the small existing Sloth does to the extinct Megatherium. The change of dentition of the Rhi- nocerotidce is, therefore, here illustrated by the young Hyrax capensis, fig. 287. The four premolars, p i, 2, 3, 4, are exposed above 287 ?n Deciduous and permanent teeth, Hyrax. Nat. size. the four deciduous molars, di, 2, 3, 4, which they push out ; the first true molar, m i, is in place ; the second, m 2, and third, m 3, molars are in different states of forwardness. The first premolar differs from the rest only by a graduated inferiority of size, which, in the last premolar, p 4, ceases to be a distinction between it and the true molars. The dental formula of the Tapir is .3.3 1.1 4^4 3.3 oo'ii*-* ** ^ * ** ** O.O I . 1 O.O O,O = 42 (vol. ii. p. 449, fig. 300, immature). The median incisors above have a broad trenchant crown, k, separated by a transverse channel from a large basal ridge ; the wedge-shaped crowns of the opposite pair below fit into the channel, and have no basal ridge ; the outer incisors above are very large and like canines ; those below are unusually small. The canines, /, have crowns much shorter than their roots, and not projecting, like tusks, beyond the lips; they are pointed, with an outer convex, separated by sharp edges from an inner, less convex, surface. The lower canines form part of the same semi- circular series with the incisors. The first three premolars above have the outer part of the crown composed of two half-cones, the posterior one having a basal ridge ; the anterior basal ridge rises into a small cusp in the second premolar, which increases in size in the third and fourth ; in this tooth the transverse depression divides at the base of the anterior and outer demicone, and the posterior division is continued into the interspace of the two demicones ; these, therefore, now become in m i and m 2 the outer ends of the two transverse wedge-shaped eminences, giving their summits a curve whose concavity is turned backward ; the last molar, m 3, may be known by the shorter and more curved pos- terior eminence. In the dentition of the lower jaw the double transverse ridged structure prevails throughout the molar series, 358 ANATOMY OF VERTEBRATES. the anterior talon being most produced and compressed in the first tooth, ]> 2. Certain huge fossil bilophodont grinders, which seemed to indicate a gigantic Tapir, are now known, by the discovery of the cranium, and the enormous tusks of the lower jaw, fig. 288, /, to belong to a genus connecting the tapiroid with the proboscidian families. The permanent dentition of the genus Dinotherium is- . o.o o.o 2.2 3.3 1.1 The two deciduous molars in situ on each side of the fragment ot the upper jaw of the young Dinotherium, which Professor Kaup 1 has figured, answer to the third and fourth of the typical series. The crown of the anterior milk-molar supports two transverse 288 \ Dentition of Dinotherium (.Kaup). ridges with an anterior and posterior basal ridge; its contour is almost square ; the last milk-molar has a greater antero-poste- rior extent, and supports three transverse eminences with an anterior and posterior basal ridge, the anterior ridge being developed into a pointed tubercle at its outer end. The two premolars, fig. 288, p 3 and 4, conform to the general rule in being more simple than the teeth which they displace and suc- ceed. The transverse diameter of the second premolar exceeds the antero-posterior one, the proportions being the reverse of those of the deciduous molar, which it displaces. The first true molar, m i, repeats the structure of the hindmost deciduous molar, its crown 1 CLXIX", p. 401 ; and cxm". Tab. i. TEETH OF UNGULATA. 359 having a disproportionate antero-posterior extent, and supporting three transverse eminences, with an anterior, posterior, and inter- nal basal ridge. The Dinothere resumes the tapiroid character, and differs from the Mastodon, inasmuch as the posterior molars? m 2 and 3, instead of having an increased aiitero-posterior extent and more complex crowns, increase only in thickness, and support two instead of three transverse eminences ; they have also an an- terior and a posterior basal ridge. In the lower jaw the first premolar, p 3, is implanted, like that above, by two fangs ; but it has a smaller and simpler crown, which is narrower in proportion to its antero-posterior extent, and is almost entirely occupied by the antero-posterior ridge, only the posterior of the two inner tuber- cles being developed ; thus the crown presents more of a trenchant than of a grinding character ; the second premolar, p 4, supports two transverse ridges. The third of the permanent series, which is the first true molar, m i, has three transverse ridges, like the one above, but is relatively narrower; the second, m 2, and third, m 3, true molars have each large square crowns, with two trans- verse ridges, and an anterior and posterior talon, the latter being more developed than in the corresponding molars of the upper jaw. The generic peculiarity of the Dinotherium is most strongly manifested in its tusks. These, fig. 288, i, are two in number, implanted in the prolonged and deflected symphysis of the lower jaw, in close contiguity with each other, and having their exserted crown directed downward and bent backward, gradually de- creasing to the pointed extremity. In jaws with molar teeth of equal size, the symphysis and its tusks offer two sizes ; the larger ones, which have been found four feet in length, with tusks of two feet, may be attributed to the male Dinothere ; the smaller specimens, with tusks of half size, to the female. The ivory of these tusks presents the fine concentric structure of those of the Hippopotamus, not the decussating curvilinear character which characterises the ivory of the Elephant and Mastodon. No cor- responding tusks, nor the germs of such, have yet been discovered in the upper jaw of the Dinotherium. D. Probnscidia. The dentition of the genus FAephas^ the sole existing modification of the once numerous and varied Probosci- dian family, includes two long tusks, fig. 289, one, i, in each of the premaxillary bones, and large and complex molars, ib., d 4, m i, m 2, in both jaws : of the latter there is never more than one wholly, or two partially, in place and use on each side at any given time, the series being continually in progress of formation 360 ANATOMY OF VERTEBRATES. and destruction, of shedding and replacement : and all the grinders succeed one another, like true molars, horizontally, from behind forwards. The total number of teeth developed in the elephant appears O Q df* to be i ' ,ra fi = 28 : the two large permanent tusks being preceded by two small deciduous ones, and the number of molar teeth which follow one another on each side of both jaws being 289 not less than six, of which the last three answer to the true molars of other mammals. The deciduous tusk appears beyond the gum between the fifth and seventh month ; it rarely exceeds two inches in length, and is shed between the first and second year. The permanent tusks cut the gum when about an inch in length, a month or usually after the milk-tusks are shed. Their widely open base is fixed upon a conical pulp, which, with the capsule surrounding the base of the tusk and the socket, conti- nues to increase in size and depth, obliterating all vestiges of that of the deciduous tusk, and finally extending its base Section of cranium and tusk of Elephant. close to the nasal aperture, fig. 289, n. The tusk, being subject to no attrition from an opposed tooth, but being worn only by the oc- casional uses to which it is applied, arrives at an extraordinary length, following the curve originally impressed upon it by the form of the socket, and gradually widening from the projecting TEETH OF UNGULATA. 361 290 apex to that part which was formed when the matrix and the socket had reached their full size. These incisive teeth of the elephant not only surpass other teeth in size, as belonging to a quadruped so enormous, but they are the largest of all teeth in proportion to the size of the body ; representing in a natural state those monstrous incisors of the rodents, which are the result of accidental suppression of the wearing force of the opposite teeth, fig. 239. The tusks of the elephant, like those of the mastodon, consist chiefly of that modification of dentine which is called f ivory,' and which shows, on transverse fractures or sections, stria? pro- ceeding in the arc of a circle from the centre to the circumference in opposite directions, and forming by their decussations curvili- near lozenges. This character is peculiar to the tusks of the Proboscidian Pachyderms. In the Indian Elephant the tusks are always short and straight in the female, and less deeply implanted than in the male : she thus retaining, as usual, more of the characters of the immature state. In the male they have been known to acquire a length of nine feet, with a basal diameter of eight inches, and to weigh one hundred and fifty pounds : but these dimensions are rare in the Asiatic species. The elephant of Africa, at least in certain localities, has large tusks in both sexes ; and the ivory is most esteemed by the manufacturer for its density and whiteness. The molar teeth of the elephant are remarkable for their great size, and extreme complexity of their struc- ture, fig. 290. The crown, of which a great proportion is buried in the socket, and very little more than the grinding surface appears above the gum, is deeply divided into a number of transverse perpendicular plates, consisting each of a body of den- tine, d, coated by a layer of enamel ib., e, and this again by the cement, ib., c, which fills the interspaces of the enamelled plates, and here more especially merits its name, since it binds together the several divisions of the crown before they are fully formed and united by the confluence of their bases p Section of molar, Elephant. 862 ANATOMY OF VERTEBRATES. 291 Molars, African Eler>h;int. into a common body of dentine. As the growth of each plate begins at the summit, they remain detached and like so many separate teeth or denticules, until their base is completed, when it becomes blended with the bases of contiguous plates to form the common body of the crown of the complex tooth from which the roots are next developed. The plates of the molar teeth of the Siberian Mammoth (Eleplms primigenius) are thinner in proportion to their breadth, and more numerous in proportion to the size of the crown than in the existing species of Asiatic Elephant. In the African Elephant, fig. 291, the lamellar divisions of the crown are fewer and thicker, and they expand more uniformly from the mar- gins to the centre, yielding a lozenge- form when cut or worn transversely, as in mastication. From this modification the gradation is close in the many extinct species to the three- ridged Mastodons and two-ridged Dinotheres. The first molars of the Asiatic Elephant include four plates, are in place and use at three months, and are shed when the elephant is about two years old. The eight or nine plates of the second molar are formed in the closed alveolus, behind the first molar by the time this cuts the gum, and they are united with the body of the tooth, and most of them are in use, when the first molar is shed. The third molar has the crown divided into from eleven to thirteen plates ; it averages four inches in length, and two inches in breadth, and has a small anterior, and a very large posterior root ; it begins to appear above the gum about the end of the second year, is in its most complete state and extensive use during the fifth year, and is worn out and shed in the ninth year. Its remains about this period are shown in fig. 289, d 4. The three preceding teeth answer to the deciduous molars, d 2, ds, and 4, above, although acquiring a relative superiority of size to its homologue in the Bear, and more decidedly a carnassial form, is not the homotype of the permanent carnassial below, but of that premolar, p 4, which displaces the deciduous carnassial, d 4. The symbols in fig. 293, m., sufficiently indicate the re- lations of the other teeth, and the conclusions that are to be drawn from them as to their homologies. In the genus Felis, fig. 260, the small permanent tubercular molar of the upper jaw, m i, has cut the gum before d 4 has been shed ; but though analogous in function, this tooth is not homo- logous with, or the precedent tooth to m i, but precedes the great carnassially modified premolar, p 4. In the lower jaw the tooth, m i, which is functionally analogous to the carnassial above, is also, as in the Dog, the first of the true molar series, and the homotype of the little tubercular tooth, m i, above. And the homologues of the permanent teeth, p 4 and m i below, fig. 293, Y., with those so symbolised in the Dog, ib. m., teach us that the teeth which are wanting in the feline, in order to equal the number of those in the canine dentition, are m 2 in the upper jaw, m 2 and m 3 in the lower jaw ; p i in the upper jaw, p i and p 2 in the lower jaw ; thus illustrating the rule, that, when the molar series falls short of the typical number, it is from opposite extremes of such series that the teeth are taken, and that so much of the series as is retained is thus preserved unbroken. VOL. III. *B B 3 374 ANATOMY OF VERTEBRATES. In the great extinct sabre-toothed Tiger, Machairodus, fig. 293, vii., the series is still further reduced by the loss of p 2, in the upper jaw. In the common Cat, the deciduous incisors, d i, begin to appear between two and three weeks old ; the canines, d c, next, and then the molars, d m, follow, the whole being in place before the sixth week. After the seventh month they begin to fall in the same order; but the lower sectorial molar, m i, and its tubercular homotype above, in i, appear before d 2, d 3, and d 4 fall. The longitudinal grooves are very faintly marked in the deciduous canines. The first deciduous molar, in 2, in the upper jaw is a very small and simple one-fanged tooth ; it is succeeded by the corresponding tooth of the perma- nent series, Avhich answers to the second premolar, p 2, of the Hyaena and Dog. The second deciduous molar, m 3, is the sectorial tooth ; its blade is trilobate, but both the anterior and posterior smaller lobes are notched, and the internal tubercle, which is relatively larger than in the permanent sectorial, is continued from the base of the middle lobe, as in the deciduous sectorial of the Dog and Hyasna ; it thus typifies the form of the upper sectorial, which is retained in the permanent den- tition of several Viverrine and Musteline species. The third or internal fang of the deciduous sectorial is continued from the inner tubercle, and is opposite the interspace of the two outer fangs. The Musteline type is further adhered to by the young Feline in the large proportional size of its deciduous tubercular tooth, d 4. In the lower jaw, the first milk-molar, d 3, is suc- ceeded by a tooth, p 3, which answers to the third lower pre- molar in the Dog and Civet. The deciduous sectorial, d 4, which is succeeded by the premolar, p 4, answering to the fourth in the Dog, has a smaller proportional anterior lobe, and a larger posterior talon, which is usually notched ; thereby ap- proaching the form of the permanent lower sectorial tooth in the Mustelidos. AY hen the premolars and the molars are below their typical number, the absent teeth, as a rule, 1 are missing from the fore- part of the premolar series and from the back-part of the molar series. The most constant teeth are the fourth premolar and the first true molar ; and these being known by their order and mode of development, the homologies of the remaining molars and pre- molars are determined by counting the molars from before back- 1 In some instances the first premolar or first milk-molar remains, of small size, when p 2 and p 3 are lost. HOMOLOGIES OF TEETH. 375 wards, e.g. ' one,' ' two,' ( three" ; and the premolars from behind forwards, ( four,' f three,' ' two,' * one.' Examples of the typical diphyodont dentition are exceptions in the actual creation ; but it was the rule in the earlier forms of placental Mammalia, whether the teeth were modified for animal or vegetable food. Not only the Hy&nodon, fig. 266, and Amphicyon, fig. 267, but the Dichodon, Anoplotherium, Palceotherium, Cheer op otamus^ An- tlirac other ium, Hyopotamus, Pliolophus, Hyracotherium, and many other ancient (eocene and miocene) tertiary Mammalian genera presented the forty-four teeth, in number and kind ac- cording to that which is here propounded as the typical or normal dentition of the placental diphyodonts. When the clue is afforded to their homologies, it infallibly conducts to the true knowledge of the nature both of the teeth which are retained, and of those which are wanting to complete the typical number. Thus may be deciphered the much modified dentition of the genus Felis ; and the same clue will guide to the knowledge of the precise homologies of the teeth in our own species. The known limits of the premaxillary in Man leads to the de- termination of the incisors, which are reduced to two on each side of both jaws ; the contiguous tooth shows by its shape as well as position that it is the canine ; and the characters of size and shape have also served to divide the remaining five teeth in each lateral series into two bicuspids and three molars. In this in- stance the secondary characters conform with the essential ones, as exhibited in the dissection of the jaws of a child of about six years of age, fig. 258. The two incisors on each side, d i, are followed by a canine, c, and this by three teeth having crowns resembling those of the three molar teeth of the adult. In fact, the last of the three is the first of the permanent molars ; it has pushed through the gum, like the two molars which are in ad- vance of it, without displacing any previous tooth, and the sub- stance of the jaw contains no germ of any tooth destined to displace it ; it is therefore, by this character of its development, a true molar, and the germs of the permanent teeth, which are exposed in the substance of the jaw between the diverging fangs of the molars, d 3 and d 4, prove them to be temporary, destined to be replaced, and prove also that the teeth about to displace them are premolars. According, therefore, to the rule previously laid down, we count the permanent molar in place the first of its series, m i, and the adjoining premolar as the last of its series, and consequently the fourth of the typical dentition, p 4. 376 ANATOMY OF VERTEBRATES. We are thus enabled, with the same scientific certainty as that whereby we recognise in the middle toe of our foot the homologue of that great digit which forms the whole foot, and is encased by the hoof, in the horse, to point to p 4, or the second bicuspid in the upper jaw, and to m i, or the first molar in the lower jaw, of Man, fig. 293, I., as the homologties of the great carnassial teeth of the Lion, p 4, m i, ib. v. We also conclude that the teeth which are Avanting in Man to complete the typical molar series, are the first and second premolars, the homologues of those marked p i and p 2 in the Bear, ib. u. The characteristic shortening of the maxillary bones required this diminution of the number of their teeth, as well as of their size, and of the canines more especially ; and the still greater curtailment of the premaxillary bone is attended with a diminished number and an altered position of the incisors. The homologous teeth being thus determinable, they may be severally signified by a symbol as well as by a name. The incisors, e.g., are represented in the present work by their initial letter i, and individually by an added number, i i, i 2, and i 3, counting from the medial line outwards ; the canines by the letter c ; the premolars by the letter p ; and the molars by the letter m ; these also being differentiated by added numerals. Thus, the number of these teeth, on each side of both jaws, in any given species, Man, e.g., may be expressed by the following brief formula : .2.2 1.1 2.2 3.3 '2V c i.i ; ^ ;m 3:3 = 32; and the homolofnes of the individual teeth, in relation to the D typical formula, may be signified by i i, z 2; c; p 3, /?4; mi, m 2, m 3 ; the suppressed teeth being i 3, p i, and jo 2. The soundness of the foregoing conclusions as to the "nature of O O the teeth absent in the reduced dental formula of Man, is exem- plified by the mode in which the type is progressively resumed in descending from Man through the order most nearly allied to our own. Through a considerable part of the Quadrumanous series, the s^ame number and kinds of teeth are present as in Man, the first deviation being the sexual disproportionate size of the canines and the concomitant break or 4 diastcma ' in the dental series for the reception of their crowns when the mouth is shut. This is manifested in Gorillas, Chimpanzees and Orangs, together with the sexual difference in the proportions of the canine teeth. Then comes the added premolar in the New World Monkeys, fig. 251, HOMOLOGIES OF TEETH. 377 p 2, and the further additions in lower quadrupeds, until in the Hog genus we see the old primitive type of diphyodont dentition resumed or retained. In the genus Sits, fig. 293 illustrates the phenomena of de- velopment which distinguish the premolars from the molars. At the stage exemplified the first premolar, 1 p i, and the first molar, m i, are in place and use, together with the three deciduous molars, r/2, d 3, and d 4 ; the second molar, m 2, has just begun to cut the gum ; p 2, p 3, and p 4, together with m 3, are more or less incomplete and concealed in their closed alveoli. The premolars displace deciduous molars in order to rise into 291 Deciduous aud perinaiieni .s,'!.^. l,i>\\<." j:\v place ; the molars have no such relations ; it Avill be observed, that the last deciduous molar, r/4, has the same relative supe- riority of size to d 3 and d 2 which m 3 bears to m 2 and m i ; and the crowns of p 3 and p 4 are of a more simple form than those of the milk-teeth which they are destined to succeed. The premolars have a more simple structure as well as smaller size, than the true molars, in all Artiodactyles. In the Ru- minants they represent only the moiety of the true molars, or one of the two semi-cylindrical lobes of which those teeth consist, with, at most, a rudiment of the second lobe. The Perissodactyles are distinguished by the size and complexity of more or less of the premolars. In Equus, p 2, p 3 and p 4, even exceed in size in i, 77*2 and in 3. In Rhinoceros and Palceotlierium the propor- tions of the molars and premolars are reversed ; but the struc- ture is the same. In Lophiodon, Conjphodon and Pliolophus the premolars become more simplified as well as diminished, ap- 1 If this tooth have not displaced a minute milk- molar, it may be reckoned a d I, which is longer retained than the rest of the deciduous molars ; in this degree the type-dentitioii is departed from. 378 ANATOMY OF VERTEBRATES. preaching to a common Ungulate type. In the Proboscidian group, the oldest species indicate retentions of type unknown in the dentition of existing Elephants. A premolar, fig. 295, p 3, displaces vertically the second deciduous grinder, ds, in some Mastodons : and, that the third molar in the order of appearance, ^/4, is also the last of the deciduous series, is indicated by the contrasted superiority of size of the tooth, m i, that follows. The great extent and activity of the processes of dental development required for the preparation of the large and complex true molar teeth, w T ould seem to exhaust the power in Proboscidians, which, in ordinary Pachyderms, is expended in developing the vertical successors of the deciduous teeth. In the miocene Mastodon above cited, this normal exercise of the reproductive force was not, however, wholly exhausted ; and one premolar, fig. 295, p 3, of more simple form than its deciduous predecessor, was de- veloped on each side of both jaws. Another mark of adhesion to the archetype was shown by the development of two incisors in the lower jaw in the young of some Mastodons, by the retention and development of one of these in- ferior tusks in the male of the Mas- todongiganteus of North America, and by the retention of both in the Eu- ropean Mastodon longirostris, Kaup. No trace of these inferior homotypes of the premaxillary tusks have been Deciduous teeth, Mastodon. i i p n t detected in the toetus or young 01 the existing elephants. In the gigantic Dinotlierium, the upper in- cisors were suppressed, and the lower incisors were developed into huge tusks, which curved down from the symphysis of the massive lower jaw. The chief modifications of the marsupial dentition have already been described and illustrated. The observed phenomena of the development and change of the teeth led to the generalisation that the marsupial differed from the placental Diphyodont mammals in having four true molars, i. e., m :-* instead of m -J:-J ; and also that they differed in having only three pre- molars, i. e. p |:| instead of p -|:-J; the typical number of the grinding series, ^;i, being the same ; and it was convenient for comparison to symbolise them accordingly, in figs. 221-230. Since, however, there is reason to conclude that m i in the pla- cental Diphyodonts, as, e. g., figs. 259 and 294, is a continuation of the deciduous series of molars, which might be symbolised as HOMOLOGIES OF TEETH. 379 d 5, and only becomes a permanent molar because there is no premolar developed above it, so we may regard the tooth marked m i in figs. 221-230 as being an antecedent tooth of the deciduous series, rendered permanent by a like reason, the suppression, viz. of p 4. In other words, that m i in fig. 227 is the homologue of d 4 in fig. 294, and that the true homologue of p 4 is not deve- loped in the Marsupialia. The homologies of the teeth of the Kangaroo are illustrated in fig. 296, according to this idea of them ; the dental formula of both the MacropodidcB and Hypsiprymnida being - . 3J5. ^ Ll 1.1. / L1 - 3.3 instead of .3.3 1.1 1.1 4.4 i ; c ; p ; m - = 30. 1.1' 0.0' 1 1.1' 4.4 The canines, which are confined to the upper jaw, are small or minute when retained ; and disappear after being represented ' en o-erme ' in most of the true Kangaroos. o o In the deciduous dentition of the great Kangaroo (Macropus major) the canines are rudimental, and are absorbed rather than shed. No other of the deciduous series is calcified, save the molars d 2 and d 3, fig. 296, unless the permanent incisors be de- veloped and retained milk-teeth. When the young animal finally quits the pouch the dentition is- j-' 1 - 2 ' 2 the upper incisors being i i, the molars d 2 and d 3 of the typical dentition. This stage is exemplified in the lower jaw at A (fig. 296). The next stage shows the acquisition of i 2 in the upper jaw, and d 4 in both jaws, and the formula is 2.2 3.3 d i ; d m -^ = 18, ib. B. l.i. o.o At one year old, the dentition is 3.3 3.3 1.1 a i ; a m ; m = z ; 1.1 O.Q 1.1 the additional teeth being i 3 and m i (ib. c), in which the demon- stration of the true deciduous character of d 2 and d 3 is shown by the germ of their vertical successor p 3, which is exposed in the substance of the jaw. The next stage is the shedding of d 2, and the acquisition of m 2 (ib. D). Then d 3 is shed by 380 ANATOMY OF VERTEBRATES. 296 Development and succession <>f the molar series, Kangaroo. HOMOLOGIES OF TEETH. 381 the ascent of p 3 into its place (ib. E). Afterwards m 3 is ac- quired ; and in the Macropus giyas, p 3, simultaneously pushed out (ib. F). Thus, four individuals of this species may be found to have the same number of molars, i. e. -J:-J ; two of these individuals may seem, on a cursory comparison, to have them of the same shape, e. g., as in c and E, or as in D and F, fig. 296. In fact, to determine the identity or difference in such instances, it requires that the substance of the jaws be examined, to see if the germs of successional teeth are present, as at p 3, C and D, or at m 3, E. The result of such examination may be to show that not one of the four Kangaroos with the m -f:-J had the same or homologous teeth. The four grinders, e. g. may be d 2, d 3, d A, m i ; as in c ; or d 3, d 4, m i, m 2 ; as in D ; or p 3, d 4, m i, m 2 ; as in E ; or d 4, m i, m 2, and m 3 ; as in F. The changes, however, do not end here. As age advances, d 4 is shed, and the molar series is reduced numerically to the condition of B ; but, instead of d 2, d 3, and d 4, it consists of m i, m 2, m 3. Finally, m i is shed, and the dentition is reduced to the same numerical state as at A ; the teeth, however, being m 2 and m 3. The symbols used, it is hoped, are so plain and simple as to have formed no obstacle to the full and easy comprehension of the facts explained by means of them. If these facts, in the manifold diversities of Mammalian dentition, were to be de- scribed in the ordinary way, by verbal definitions, e. g., ' the second deciduous molar representing the third in the typical dentition,' instead of d 3, and so on, the description of dental development would continue to occupy much unnecessary space, and would levy such a tax upon the attention and memory as must tend to enfeeble the judgment and impair the power of seizing and appreciating the results of the comparison. Each year's experience has strengthened the writer's convic- tion that the rapid and successful progress of the knowledge of animal structures, and of the generalisations deducible therefrom, will be mainly influenced by the determination of the homology of parts and organs, and by the concomitant power of condensing the propositions relating to them, and of attaching to them signs or symbols equivalent to their single substantive names. In the writer's Works, CXL, CXLI, CXLIY, he has denoted most of the bones by simple numerals. The symbols of the teeth are fewer 382 ANATOMY OF VERTEBRATES. ill number,, are easily understood and remembered, and, if gene- rally adopted, might take the place of names. They would then render unnecessary the repetition of phrases, harmonise con- flicting synonyms, serve as a universal language, and at the same time express the expositor's meaning in the fewest and clearest terms. The entomologist has long found the advantage of such o o o signs as and $ , in reference to the sexes of insects, and the like ; and it is hoped that the time is now come when the ana- tomist may avail himself of this powerful instrument of thought, instruction, and discovery, from which the chemist, the astro- nomer, and the geometrician have obtained such important results. MOUTH OF MAMMALS. 383 CHAPTER XXX. ALIMENTARY CANAL AND APPENDAGES OF MAMMALS. 223. Mouth. Fleshy lips form the main characteristic of the mammalian mouth. But they are wanting in the Monotremes, with other significant shortcomings of mammalian excellence. Lips are, here, transitorily manifested, it is true, at the suckling period ; but soon degenerate into the pergameneous border of the beak in Platypus, and are reduced, in Echidna, to the scarcely movable margin of the small terminal oral orifice of the adult. The Cetacea show the greatest extremes within the limits of a natural group in the development of the lips. They are barely represented in the Porpoise, fig. 297, and other Delphinidce by 297 Section of mouth and nose, Porpoise. the low, firm, ridge of integument, supported by adipo-fibrous tissue with scarce a trace of f orbicularis oris ' : while in the Whale (Balcena) the upper lip falls down like a thick curtain some feet in depth concealing the baleen, and overlapping the 384 ANATOMY OF VERTEBRATES. inaudible when the mouth is closed. The side-walls of the mouth are not dilatable and contractile so as to vary the capacity of the buccal cavity, like the ' cheeks ' in most other mammals. As a rule, in the present class, the mouth is terminal : when not so, a rostral production, analogous to that in Sharks, makes the open- ing inferior, as in the Tapir, fig. 155. In the Chrysochlore the mouth is a small triradiate slit, like that of a leech, on the under surface of the muzzle : it. has a like inferior position, but is more deeply cleft in Shrews, in which the groove that runs along the mid-line of the under surface of the snout represents the third ray of the closed mouth. The remoteness of the mouth from the end of the muzzle is in the ratio of the length of the latter : consequently, among the Shrews, it is greater in those (Petrodromus, Rliyncliocyon, fig. 298) which, from the production of the snout, have been called f Elephant Mice': still more so in the Elephant itself, vol. ii. fig. 162. The Ornithorhyiichus subsists on aquatic insects, larva?, mol- lusks, and other small invertebrates which conceal themselves in the mud and banks of rivers, and is provided with a mouth nearly resembling the flat and sensitive bill of a lamellirostral bird. The jaw-bones are invested by a smooth coriaceous integu- ment, vol. ii. fig. 199, A, E, a, devoid of hair, but perforated by innumerable minute foramina. At the base of the jaws this in- tegument is produced into a free fold, which overlaps the hairy covering of the cranium immediately behind it. The integument covering the upper mandible extends beyond the margins of the bone, and forms a tumid, smooth, and highly sensible border ; the narrower and shorter under jaw is more closely invested : the oral or upper surface of the lateral part of the under jaw supports a series of about twenty nearly transverse folds, increasing in breadth as they approach the angle of the jaw: the corresponding surface of the upper jaw is smooth. On the outside of the pos- terior part of each molar in the lower jaw, is the orifice of an oblong cheek-pouch, fig. 3, r, F, about two inches in length, and half an inch in diameter : the pouch is continued backward, and is lined with a hard dry cuticle. The raised posterior lobe of the tongue, fig. 2 1 2,/, with the projecting horny bodies,//, #, can impede the passage of unmasticated food to the pharynx, and direct it on each side into the cheek-pouches ; whence the Ornithorhynchus may transfer its store at leisure to the molar teeth, and complete MOUTH OF MAMMALS. 385 its preparation for deglutition. An air-breathing warm-blooded animal, which obtains its food, while submerged, by the capture of small aquatic animals, must derive great advantage from the structure which enables it to transfer them quickly to a temporary receptacle, whence they may be extracted and masticated while the animal is floating on the surface or at rest in its burrow. The soft palate is thick, broad, and divided posteriorly into three fimbriated lobes. The pharynx is narrow, and is encom- passed by two posterior processes of the thyroid cartilage, fig. 212, c, c. The long tubular mouth in Echidna, like that in the Ant- eaters, is remarkable for its small orifice, fig. 302. The palate is armed with six or seven transverse rows of strong, sharp, but short retroverted spines. The tongue is long and slender, as in the true Anteaters ; its dorsum is broad, flat, callous, and beset with hard papillae, and the insects are doubtless crushed between these and the palatal spines. As, however, the food undergoes less comminution in the mouth of this Monotreme than in that of the Ornithorhynchus, the pharynx is wider. The jaws of the Marsupialia are covered by well-developed fleshy lips ; the upper one is partially cleft in the Kangaroos, as in some Rodents ; the muzzle is clad with hair in Macropus major and a few other species ; but in most Marsupials it is naked, and generally red from the vascularity of the integument. The palate is sculptured with transverse ridges. These are most numerous in the Bandicoots, being fourteen in the Perameles nasuta, and are slightly curved forwards : the roughness thus produced must aid the tongue in retaining small insects. In a few species of Marsupials I have detected cheek-pouches. In the Koala they are wide and shallow, situated one on each side of the upper lip ; the orifice is opposite the first superior premolar, and leads forward above a horizontal fold of the mucous membrane which attaches the upper lip to the side of the premaxillary bone, separating this part of the cheek-pouch from the mouth. In the Perameles lagotis there are also two small fossae, one on the inside of each cheek, about four lines in diameter, and lined by a very distinct white epithelium. The aquatic Opossum {Didelphys Yapock) has large cheek-pouches, extending far back into the mouth, in which, like the Ornithorhynchus, it may stow away fresh-water insects, Crustacea, &c. The fauces are wide in the zoophagous, but narrow in the entomophagous and phytophagous Marsupials. The tonsils are represented by a pair of small glan- dular cavities. 1 1 xx. vol. iii. p. 81. VOL. III. C C 38G ANATOMY OF VEBTEBEATES. 299 In Rodentia the scalpriform incisors are commonly more or less exposed in front of the mouth ; and, as their office is to re- duce the food to small bits, the mouth is small. A groove running thereto from the nostrils divides the upper lip, conspicuously so in the species which has suggested for this modification in other animals the name ' hare-lip.' But in a few Rodents, e.g. Mole- rats ( Orycteropus, Spalax), the undivided upper lip surrounds the bases of the huge pair of incisors by a kind of hairy sheath, and the lower lip is similarly modified in relation to the prominent lower incisors. The hairy integument is continued or reflected within the mouth in some degree in most Rodents. In the Paca ( Cceloyenys) it is continued along the inside of the cheeks, with an accession of glandular follicles ; then, losing the hair, it lines a large cavity formed by the singular expansion of the zygomatic process of the maxillary and by the malar bone, vol. ii. fig. 237, 21, 26. Some Rodents have dupli- catures of the buccal mem- brane, outside the zygomata, and capable of expansion, for storage and conveyance of alimentary substances. Fig. 299 shows these ' cheek-pouches' in Geomys 7 . A -i 1 oursanus, everted and m- Claeek-pouches of the Canada Hat (Gcoinya bursarius). n i i Hated : a more natural view of this buccal appendage is given in the dissection, fig. 300, of the head of an African pouched rat. In this species (Sacco- stomus lapidarius, Peters) an orifice at the angle of the mouth leads to the pouch, widening from the orbit to the lower border of the mandible, and reaching back as far as beneath the ear. In the Ham- ster ( Cricetus) the wide orifice of the pouch is just within the com- missure of the short lips : the bag itself extends along the side of the Cheek-pouch (Saccostomus). LXXXIV." 111 i rrM n head to the neck. I he orifice has a sphincter, and from this there diverge longitudinal fasciculi back- ward over the Avail of the cavity, Avhich is also provided with fibres from the dorso-lateral panniculus carnosus : these tending to retract the pouch-walls, while the others draw them forward, and both combining to empty the pouch. Saccomys and Spermophilus 300 MOUTH OF MAMMALS. 387 have similar cheek-pouches. The roof of the mouth between the incisors and molars is narrow and ridge-like : as it expands posteriorly it is commonly beset with two rows of hard oblique rido-es. In no mammalian order is the food so much reduced by O mastication as in Rodents, and many of them show concomitant modifications of the fauces ; such as the constriction of the soft palate in the Capybara, reducing the communication between the mouth and pharynx to a small aperture. In Capromys the upper lip is furrowed longitudinally, but not bifid. On the middle line of the palate, between the incisors and molars, are three distinct hard white tubercles : the first, the largest and most prominent, is situated about half-an-inch behind the incisors; the second, which is the smallest of the three, is at a distance of three lines from the former ; and immediately behind it is the third. On each ' / side of the first tubercle there is a softer one situated on the margins of the upper lip. The gape of the mouth is wide in insectivorous Cheiroptera. Some bats have a modification of the integument for an analogous office to the cheek-pouches in a part of the body remote from the mouth : the skin extended from the hind-legs to the incurved tail (interfemoral membrane) forms a bag into which flies are beaten, inclosed, and stored. The frugivorous kinds have not this structure. In Nycteris two converging ridges of the lower lip inclose a triangular prominence of the upper lip. In Otoops the upper lip is transversely grooved. In Noctilio it is dependent. The palate is transversely ridged, the hinder ones usually divided by a medial cleft. The tongue can be protruded far in Cheiroptera ; and, when retracted, usually shows transverse (Mormoojjs) or oblique foldings of the dorsum : the minuteness or absence of incisors permits protrusion even when the molars are in a state of apposition. Bats use the tongue in lapping ; also in licking off the juice of fruits, as e.g. in the tropical Phyllonycteris. The tip of the tongue is spinulose in Rhinopoma. In the Vampire (Desmodus, Phyllostoma) the ter- minal papillae resemble wart-like elevations, so arranged as to form a circular suctorial disk when they are brought into lateral contact by the action of a set of muscular fibres thereto adapted. Some bats (Saccolaimus) have a gular pouch : in Molossus this seems to be sexual, and is peculiar to the male. In the order Bruta, the mouth is remarkably short in the Sloths, and attains its maximum of length and narrowness in the Ant- eaters in which it seems to be mainly a sheath for the retracted C C 2 388 ANATOMY OF VERTEBRATES. tongue. The buccal orifice, fig. 9, a, is little wider than is needed for the protrusile and retractile movements of that slender organ, so singularly modified for the prehension of the Termites which form the staple food of the so-called ' anteaters.' The tongue in Myrmecophaga jubata, ib. I, is covered by a smooth shining epithelium, which begins to present a softer, more vascular or mucous character fourteen inches from the apex, but the only papillae anywhere visible are two fossulate ones, two lines apart, situated on the dorsum, about two inches in advance of the termination of the fraenum. A linear groove, commenc- ing two inches from the base of the tongue, extends along the dorsum to within four inches of the apex. The muscular sub- stance of the free part of the tongue is formed by the intrinsic fibres, or f linguales,' and by the lingual portions of the sterno- glossi, genio-glossi, and epihyo-glossi (p. 23). The buccal mem- brane is smooth, perforated at its lateral and inferior parts, and also superiorly beyond the bony palate, by innumerable very minute orifices, from a quarter of a line to one line apart, by which the secretion of a thin glandular stratum behind the mem- brane enters the mouth. Four inches in advance of the angle of the jaw, near the lower border of the ramus, a longitudinal ridge or low fold of the buccal membrane begins to rise, increasing in O J O depth and assuming a callous hardness as it extends forward and upward : this ridge is about two lines in breadth, and bends down so as to leave a groove between it and the lower membrane of the mouth. Introduced termites may be crushed by the action of the tongue against these two callous ridges, which seem to occupy the place of teeth on each side of the mouth. In the two-toed Anteater they take the form of a horny molar plate on each side of both jaws. The cavity of the mouth quickly expands as it passes backward, and acquires its greatest breadth opposite the base of the tongue, ib. o verse fibres than in the tongues of most other Mammals : the contraction of the longitudinal fibres taking place with the re- laxation of the transverse ones produces the retraction of the whole organ. The nerves of the tongue present the same dis- position as those in ordinary Ruminants, but the ninth pair is relatively larger than the branch from the fifth pair ; the nerve which runs along the inner or under surface of the stylo-glossi toward the free extremity of the tongue is remarkable for its beautifully wavy course, by which it is accommodated to the variations which occur in the length of the organ in the living animal. The back of the mouth appears to be as completely closed in the Giraffe as in the Capybara ; but, instead of contracting, like a funnel, to a small circular depression, it terminates by a transverse slit, through which projects the broad upper margin of the epiglottis, which is folded upon itself. The faucial membrane is coarsely corrugated. 1 The velum palati descends to the inter- space between the epiglottis and the large arytenoid cartilages ; and there is an uvular process from the middle of the inferior margin. The tonsils are well- developed glands of a flattened oval form, having each a short duct communicating by one wide opening with the fauces. 1 xcvn'. pi. xlii, fig. 3. MOUTH OF MAMMALS. 395 The back of the mouth, in Ruminants, presents its chief modi- fications in the Camel-tribe. A broad pendulous flap hangs down from the fore part of the soft palate and usually rests upon the dor- sum of the tongue. The velum palati extends beyond this process, some way down the pharynx and terminates by a concave border. The pharynx behind the velum dilates into a sac. In the rutting male the palatal flap is greatly enlarged. I have found it extend- ing ten inches down the pharynx, passing below the margin of the soft palate and the opening of the larynx, into the O3sophagus : in the living animal it is, at this season, occasionally protruded, with a belching noise, from the mouth. Its surface shows the pores of innumerable mucous crypts, and in the ordinary state, in both sexes, the flap may apply its own secretion, and water regur- gitated from the storage-cells of the stomach, to the extended surface of the pharynx and root of the tongue, so as to allay the feeling of thirst and help the animal to endure the long remis- sions of drinking to which it is liable in traversing the desert. The mouth in Carnivora is characterised by the width of its gape, and the mobility, dilatability, and contractility of its mus- cular and membranous walls. Cheek-pouches have not been found in any species. The great extent of faucial membrane between the back of the tongue and the larynx, with the coex- tensive soft palate in the Lion and some other large Felines, has been adverted to (p. 198); also the retroverted spines, and the lytta of the tongue in connection with the work of the mouth, in certain Carnivora. In the Hyasna the tonsils are relatively larger than in the Lion. The palatal gum is transversely ridged in most Carnivora. The provision for the lubricating mucus at the back of the mouth and fauces is much less in the present than in the hoofed group of Mammals. In Quadrumana the Cercopitheci, Macaci, and Cynocephali have cheek-pouches, the slit-like orifices of which are a little within the labial commissure ; the cavity extends outside and below the mandibular rami, where it is occasionally seen much distended with food. The Semnopitkeci and Colobi, remarkable for their large sacculated stomachs, have not such cheek-pouches : they are wanting also in Lemuridce, Platyrhines, and tailless Apes. The Lemuridce have the palatal gum ridged. In the Aye-aye ' there are three curved transverse ridges anteriorly, convex for- ward, followed by four transverse pairs of similar ridges. In other Lemur idee the palatal ridges are similarly curved, but 1 en', p. 41, pi. xii, fig. 6. 396 ANATOMY OF VERTEBRATES. usually undivided, from five (Potto) to eight or nine (Galago) in number : between the two anterior ridges are the orifices of canals leading from the palate to the nose. The uvula is represented in the Aye-aye and some other Le- muridce by a medial longitudinal fold from the back of the soft palate close to the margin, but does not project so as to divide the fauces into two arches : this form of soft palate begins to appear in Platyrhines : in the Baboons the uvula is thick and short : in the Apes it approaches nearer the proportions of that appendage in Man. In the higher Quadrumana the palate is smooth, or unridged, as in Man. 224. Salivary Glands. Fluids of different properties are poured into the mouth in aid of its various functions of receiv- ing, retaining, comminuting, softening or dissolving, tasting, and transmitting throatward, the food. For the preparation of these fluids corresponding modifications of glandular parts exist, from the simple mucous follicle to aggregates of three or of more complex follicles, with further multiplication and compaction of secerning surfaces, in groups and bodies, forming glands and ducts with definite names. As the function of the mouth is simplified so is the condition of such ministering glands. In the piscivorous Cetacea, which bolt their food like fishes, the parotids and submaxillaries are not present : the latter are represented with the sublinguals, in a diffused form in whalebone whales. The parotids are large in Sirenia ; * their ducts open in the Manatee on two papillae, one on each side the fore part of the palate : in the Dugong the parotids are situated immediately behind the ascending mandibular rami : there is a thick layer of mucous glands above the membrane covering the hard palate. In the Ornithorhynchus the parotid, fig. 3, E, is divided into flat portions or lobes thinly applied to the fundus of the cheek- pouch and anterior to the long meatus auditorius. The sub- maxillary, ib. D, is a moderately-sized, oval, compact body, situ- ated behind and below the meatus auditorius. The duct passes under the omo-mylo-hyoideus, ib. 10, and then, contrary to the usual mode, begins to be disposed in a series of about twelve close transverse folds, and terminates by a simple aperture at the fraenum linguae. In the Echidna the submaxillary gland, fig. 302, by is of unusual dimensions : it extends from the meatus audi- 1 cxvn". p. 29. SALIVARY GLANDS OF MAMMALS. 397 torius along the neck, and upon the anterior part of the thorax : it is a broad, flat, oblong tabulated body, narrowest at its anterior extremity, from which the wide duct emerges. When the duct 302 Submaxillary glands, Echidna setosa; nat. size. has reached the interspace of the lower jaw, it dilates, and then divides into eisfht or ten undulating branches, which subdivide o o y and ultimately terminate by numerous orifices upon the mem- 308 ANATOMY OF VERTEBRATES. branous floor of the mouth. This modification of * Wharton's duct ' appears to be unique. The large size of the glands and the mode in which the secretion is spread over the floor of the mouth relate to the lubrification of the long, slender, and exten- sible tongue, and to its fitness as an instrument for obtaining the insect food of the spiny Monotreme. The salivary glands in the carnivorous Dasyures consist of a small parotid and a large submaxillary gland on each side. They do not agree with the dogs in having the zygomatic glands. The submaxillary is placed in front of the neck, so that its duct passes on the dermal side of the tendon of the biventer maxilla, and terminates half an inch from the symphysis menti. There is a thick row of labial glands along the lower lip. The Opossums and Bandicoots present a similar salivary system. In the Pha- langista vulpina there is a sublingual gland on each side of a firm texture, about one inch in length and three lines broad ; a roundish submaxillary gland about the size of a hazel-nut ; and a broad and flat parotid, larger than in the entomophagous or sar- cophagous Marsupials. The parotid glands are relatively larger in the Koala, in which the duct takes the usual course over the masseter and enters the mouth opposite the third true molar, counting backwards. In the Wombat I found the parotid glands very thin, situated upon both the outer and inner side of the broad posterior portion of the lower jaw; the duct passed directly upwards and outwards to the insertion of the sterno-cleido-mas- toideus ; here it was buried in the cellular substance anterior to that muscle, then turned over the ramus of the jaw, and, pur- suing a somewhat tortuous course over the masseter, entered the mouth just anterior to the edge of the buccinator. The sub- maxiilary glands were each about the size of a walnut ; their ducts terminated as usual on each side of the fraenum line-use. In o ihe great Kangaroo the parotid is very large, extending from below the auditory meatus three or four inches down the neck : In the Potoroos it reaches as far as the clavicle. In both genera this gland is separated from the submaxillary gland by the sub- maxillary vein. The sublingual glands are elongate, but of mo- derate size. The tonsils are small in all the Marsupials, but are not represented in the carnivorous species, as in the placenta! Ferag, by simple glandular pouches at the sides of the fauces ; for example, they consist of an oblong glandular body on each side in the Dasyurus macrurus. In Rodents, as in Marsupials, the proportions of the parotid and submaxillary differ according to the nature of the food. In the SALIVARY GLANDS OF MAMMALS. 399 omnivorous rats with ferine tendencies, the submaxillaries are in excess : in most other Rodents which subsist mainly or ex- clusively on vegetable products the parotids are the largest. They are enormous in the Beaver, extending from before the ears forward and downward to contact with the submaxillaries, which are about one-twentieth their size ; the whole forming a sort of glandular collar : the buccal glands are numerous. In Leporidce the parotids partly inclose the base of the ear-conch and also descend to meet the submaxillaries : the parotid duct crosses the upper part of the masseter and terminates opposite the last upper molar tooth. The submaxillary duct terminates at the side of the frsenum linguae : the submaxillaries are thin and long: the chief mass of the molar follicles is near the upper molars. The submaxillary glands are almost as large as the parotids in the Paca (Coeloye?iys): both glands are large: the latter present a compact reddish tissue. There is also a large zygomatic salivary gland, which exists, of smaller relative di- mensions, in the Guinea-pig (Aperea). In the Hamster the parotids are elongate, narrow, and applied, as in the Ornitho- rhynchus, to the back of the cheek-pouches : there is also an accessory lobe, beneath the masseter. The submaxillaries are large, round, and of a reddish colour. The sublinguals are small, subglobular. In Bathyergus the salivary glands are smaller than in most other Rodents. Amongst Insectivora the hedgehog is remarkable for a zygo- matic gland which seems to be a development of the homologue of the ' molar ' glands in Marsupials. The parotids are larger than the submaxillaries ; but both are well-developed. The sub- lino-ual follicles are in two series, the larger one next the mandi- JT5 O bular ramus. The mole has large parotids and submaxillaries, the former oblong, the latter subdivided into roundish masses : the sublingual is placed very near the mandible : there is no zygomatic gland. In shrews the maxillary exceeds the parotid gland in size : the latter follows the auditory meatus in its in- ferior position. The same proportions hold in the insectivorous bats : but in the fruit-eating Pteropines the parotids are the larger glands. o ~ Great is the diversity of the salivary system in the order Bruta, as the difference of food and ways of getting it might indicate. The parotids are somewhat less than the submaxillaries even in the phyllophagous Sloths, and are much the smallest in the in- sectivorous families. In the Armadillos the parotid gland is small : its duct opens into the mouth near the angle of the lips. The 400 ANATOMY OF VERTEBRATES. submaxillary glands are very large, subcervical in position, extend- ing from the angle of the jaw to the anterior border of the pectoralis 303 major, where they meet at the middle line, under-lap- ping the sterno - hyoidei. The gland, fig. 303, c, 1 is lobular, and sends its se- cretion by three or four short ducts, d, d, into a pyriform bladder, e, situ- ated at the fore part of the gland, from the apex of which the duct, f, is con- tinued forward to terminate by a minute orifice on the sublingual membrane of the mouth, immediately behind the symphysis menti. The saliva which the bladder contains is tenacious, the serous part being probably absorbed during its deten- tion. Thus prepared and accumulated it is expelled at the fore and under part of the mouth, in order to lubricate the tongue. In the great Anteater the submaxillary salivary gland is a bilobed body, sixteen inches in length, two inches in greatest thickness at the posterior part where the two glands blend together. 2 From this confluent base they diverge, extending outward and forward, and form, each, a flattened triangular mass, from four to five inches in breadth 1 cxxvn". p. 144. The preparations which exemplify this modification of the salivary system are Nos. 772 L, and M, in xx, vol. i. p. 238 (1831). Prof. Rapp, in cxxix". (1843), refers, for this structure, to WINKER, Dissert, sistens observationes anatomicas de Tatu novemcincto. Tubing. 1826, pp. 10, 11 : RAPP, prgeses ; who adds: ' Nachdem Prof. Jager, in Stuttgart, sie schon vorher bemerkt hatte.' This inaugural Thesis I had not seen at the date of vm", and I became aware of its existence only through the reference thereto in Prof. Rapp's work. 2 vm". pi. 40. Salivary gland and bladder, Armadillo. SALIVARY GLANDS OF MAMMALS. 401 and two inches thick posteriorly, and becoming thinner towards the outer and anterior border, where the apex is prolonged into a slender process. The isthmus, or base of the combined glands, overlies the anterior half of the thorax ; the base of each lateral lobe is notched by the prominence of the shoulder-joint, round which its outer border extends ; the contracting anterior * O prolongations of the gland pass forward along the sides of the neck, external to the sterno-maxillaries, and terminate a little in advance of the angle of the jaw. The tAvo packets of ducts, which indicate the essential double- ness of the gland, emerge from the inner and posterior part of the lateral lobes, five or six inches in a straight line from the posterior border of the isthmus, and nine or ten inches from the anterior attenuated extremity of the gland. After a short course, the ducts dilate and form a small reservoir on each side ; they are here so closely covered and connected by elastic cellular tissue as to seem a single reservoir ; they maintain, however, their distinctness, and continue, contracted, from each dilatation, as three closely united attenuated ducts, which at length unite into one long and slender duct. The dilated portion is sur- rounded by a compressor muscle (constrictor salivaris). The gland is conglomerate, the primary lobes being for the most part oblong, subcompressed, from about three to nine lines in diameter. The closely united ducts, after quitting the reser- voir, are continued forward covered by the extraordinarily ex- tended mylohyoideus, and, after their union, the common duct terminates at the symphysis of the lower jaw. The parotid gland is small in proportion to the animal : it is situated in front and below the root of the ear, is of a triangular form, two inches four lines in length, one inch two lines in breadth, with the duct continued from the outer side of the an- terior apex of the gland, which apex terminates at the posterior end of the origin o f the masseter muscle. The duct extends for- O ward along the outside of the masseter near its origin, passes along the buccinator near its upper border and beneath the ten- dons of three of the retractors of the mouth, then dips under the orbicularis oris, and terminates near the opening of the mouth. The length of the duct is eleven inches, its diameter scarcely half a line. This is perhaps the longest duct, in proportion to the size of the gland, in the animal kingdom : as the submaxillary is the largest gland outside a visceral cavity in the vertebrate series. The depressor auris, which arises from the angle of the jaw, perforates the parotid gland. A chain of lymphatic glands VOL. III. D D 402 ANATOMY OF VERTEBRATES. is continued backward from beneath the parotid on The side of the neck. The representative of the ( snblingnal gland ' forms a thin layer, divided for the most part into narrow elongated lobes or groups of follicles, attached to and spread over the inferior buccal mem- brane for an extent of twelve inches: the greatest breadth of this layer is two and a half inches, and is opposite the angle of the jaw. There is a small elongated f labial gland,' lying upon the fore part of the buccinator, near its lower border, and sending its secretion into the side of the fore part of the mouth ; apparently to lubricate that contracted aperture during the frequent and rapid protrusive and retractile movements of the tongue. The t buccal glands' form a very extensive but extremely thin stratum of muco-glandular follicles, closely attached to the thin membrane of the mouth ; they are chiefly developed at the lower and lateral parts, and along the middle of the upper surface of that part of the mouth which is prolonged backward, below the similarly pro- longed nasal canal, beyond the bony palate. These glands ter- minate by innumerable very minute orifices upon the smooth inner surface of the buccal membrane, which they serve to lubri- cate. They are continuous with the better-marked series of follicles extending along the sides of the under surface of the mouth, beneath the lower jaw, which represent the ' sublinguales.' But the glands that pour out the abundant viscid secretion Avhich lubricates the tongue and is mainly subservient to its peculiar prehensile function in the Great Anteater, are those conjoined or interblended pair that answer to the submaxillary salivary glands in other animals ; which glands are most modified and developed, for a like function, in other species of Myrmecophaga, and, as we haA-e seen, in the Armadillos (Dasypus), and in the Echidna, In the little scansorial Myrmecopliaga didactyla, the homologues of the submaxillary glands are subcervical and blended together, as in the larger species ; and a slender process is continued from them to the labial gland. The duct commences by three tubes continued on each side from the main body of the gland ; and these tubes dilate into a small reservoir, provided with a com- pressor muscle, before the long and slender single duct is continued, covered by the mylohyoideus, to the symphysis of the jaw. The parotid gland is of very small relative size ; and this striking difference in the proportions of the two chief salivary glands indicates the difference in their functions and in the quality of their respective secretions. The labial glands are relatively larger in the Myrmecophaga didactyla than in the Myrmecopliaga SALIVARY GLANDS OF MAMMALS. 403 jubata ; and there is a superadded aggregate of mucous follicles behind the eyeball, in the shallow orbit of the smaller species, the secretion of which enters near the angle of the mouth. In the Hyrax the parotid exceeds the submaxillaiy in size, and is of a redder colour : the sublinffiial is almost as laro'e as o the latter. In the Horse the parotid forms a considerable mass extending from its normal position behind the masseter, upward to the ear-conch, the base of which it embraces, and downward to the larynx, where it meets its fellow. Three ducts quit the mass at different points of its lower half, converge and unite as they pass downward and forward ; the common duct, which curves down beneath the lower border of the masseter, rises in front of that muscle to pierce the buccal membrane at a papilla opposite the last upper premolar. The submaxillaries are about one-fourth the size of the parotids, by which they are covered : the gland extends from the transverse process of the atlas to the angle of the jaw. The duct terminates on a valvular papilla anterior to the fraenum linguae. The sublingual glands, beneath the sides of the fraenum, are elongate, as large as the submaxillaiy, and communicate with the mouth by several orifices. The buccal glands form large tracts of lenticular follicles along the upper maxillary bone, ascending to beneath the zygoma. In the Hog-tribe the parotids have a large proportional size : the duct follows the lower border of the masseter, curves upward, and opens into the mouth opposite the last premolar : there is a small patch of buccal glands near its termination. In the Baby- roussa and Wart-hog the parotid extends from its normal position, downward and backward, to the shoulder-joint and, mesiad, to the sterno-thyroids : resembling in size, shape, and proportion, the siibmaxillary of the Armadillo : its duct crosses the upper part of the masseter. As in the Hog, there are two sublingual glands ; one, which is very long and narrow, accompanies the duct of the submaxillaiy gland, and is composed of small lobes of a pale reddish colour ; the orifice of its excretory duct is near that of the maxillary. The second sublingual gland is placed in front of the former, and is of a square form; it discharges its secretion through eight or ten short ducts, which pierce the mucous membrane of the mouth. Dr. Ward has given an illus- tration, fig. 304, from a preparation by Quekett, of the distri- bution of the capillaries in the parotid of a Pig. The arteries penetrate the areolar tissue at different points of the surface, and are conducted, as it were, by this tissue through the interlobular spaces as far as the primary aggregations of the vesicles, where D D 2 404 ANATOMY OF VERTEBRATES. 304 Capillaries of Parotid of Pig, niagn. cxxv". they form a network, which is distributed over the elementary parts of the gland. The parotids are large in all Ruminants. In the Ox the parotid is vertically extended behind the long ascending mandibular ra- mus from the lower border of the ear-conch to the angle : the duct, as in the Horse and Hog, follows the lower contour of the mas- seter, and penetrates the mouth opposite the first upper true molar. The submaxillary lies be- hind and upon the angle oi the jaw: it is relatively larger than in the horse ; its duct traverses the sublin- gual gland in passing to its termination below the fringed fore part of the fraenum. In the Giraffe its opening is similarly pro- tected by a small valvular papillose fold. There are three small elongate masses of buccal glands, over the alveoli of both upper and lower molar series : opening upon the angle of reflection of the gum-membrane upon the cheeks or lips. In the Carnivorous order the salivary system is least developed in the Seal-tribe : they have the parotid either very small or wanting: and have no zygomatic glands. In the Dog the pa- rotid, fig. 305, , is comparatively small, flat externally, with the duct continued from near the lower end, and traversing the masseter, in an almost straight course, at an equal distance from the upper and lower borders of the muscle : it terminates opposite *he upper carnassial, ib. b. The submaxillary, ib. c, is a large globose gland, beneath and partly covered by the parotid behind the angle of the jaw: its duct terminates at d'. The sublingual, ib. e, is more posteriorly placed than in Ungulates, and is in contact with the submaxillary, of which it seems an accessory lobe : its duct, f, has a similar termination at the fore part of the fraenum lingua?. The zygomatic gland, ib. y, seems to be a special development of part of the buccal system : its duct, h, terminates behind that of the parotid, opposite the interval be- tween the penultimate and last molars. The parotid is relatively larger in the Cat, and more so in the Bear-tribe. SALIVARY GLANDS OF MAMMALS. 405 In the Aye-aye the parotid, of a subtriangular flattened form, extends from its usual position to beneath the mandible where it is in contact with the submaxillary gland. The duct leaves the parotid about three lines above the lower margin of the mandible, 305 Salivary glands of Dog. iv". crosses the masseter, and penetrates the buccal membrane close to tne angle of the mouth. The submaxillary is smaller, thicker, more globose and compact in texture. 1 These forms and propor- tions of the two main salivary glands obtain in all Lemuridce: in Stenops the authors of cxxiv" describe and figure 2 the ducts of the submaxillaries as uniting, beneath the middle of the tongue, into a common duct which passes backward to terminate upon the mucous membrane of the mouth a little above the hyoid. In the Potto the submaxillary ducts open in the usual position, upon the free margin of the sublingual. In the higher Quad- rumana the salivary system accords, in the main, with that in Man. The situation of the submaxillary agrees with the name of the gland. The buccal follicles are more numerous in the cheek- pouched monkeys, and the parotids are relatively larger in the more exclusive vegetarians. The human parotid is a depressed, three-sided pyramid : its base forms the exterior surface, and the apex sinks deep to the stylo-hyal and its muscles, penetrating between them and the internal pterygoid muscle, as far as the pharynx. A dense fascia separates it from the submaxillary : that which covers its base is called ( parotid fascia : ' and the gland is attached by similar tissue, posteriorly, to the cartilage of the meatus auditorius. A portion of the gland which extends from the part overlapping 1 en', p. 43. P 52, pi. i, fig. 5. 40G ANATOMY OF VERTEBRATES. the massetcr, forward below tlic zygoma, is called ( socia pa- rotidis ; ' and in some cases it sends its secretion by one or two small tributary canals into the main duct. This crosses the */ massetcr, perforates the buccinator, glides between that muscle and the mucous membrane of the mouth, which it finally per- forates opposite the penultimate upper molar, m 2. The parotid derives its arterial supply from the ectocarotid, directly and through the medium of branches ; the disposition of the terminal capillaries resembles that shown in fig. 304. The nerves are derived from the facial, the anterior auricular, and the ex- ternal carotid plexus. The submaxillary gland, much smaller than the parotid and larger than the sublingual, is situated in the anterior portion of the digastric space. It is irregularly ob- long in form, and is enclosed in a loose investment of areolar O y tissue more delicate than that covering the parotid. Its long axis is directed from before backward, and is about an inch and a half in extent. Its external or maxillary surface is slightly concave, is lodged in a groove in the bone, and is in immediate contact with the mylo-hyoid nerve. The anterior extremity is the smallest, and from the part represented by the confluence of the inner and outer surfaces above, generally proceeds a process, longer than the gland itself, and passing along the upper surface of the mylo-hyoid muscle in company with the excretory duct, but above it, as far as the sublingual gland in front, with which it is occasionally incorporated. This process may be regarded as analogous to the accessory gland of the parotid, and like it varies considerably in size and relation to the body of the gland. A quarter of an inch below the base of the process appears the com- mencement of the excretory duct. It accompanies the gustatory nerve toward the tip of the tongue between the sublingual gland and the genio-hyo-glossus muscle to the side of the fraenum lingua? : in the terminal part of its course it is directed forward and inward, fig. 306, b, lies immediately beneath the mucous membrane, and opens by a very narrow orifice into the mouth, in the centre of a papilla of mucous membrane which projects from the side of the fraenum. The duct is about two inches in length, its coats are more delicate and extensible than those of the parotid. Its calibre exceeds that of the parotid duct, and, like it, its narrowest portion is that immediately beneath the mucous membrane, and this gradually contracts more and more, so that the terminal orifice becomes so small as scarcely to be visible by the naked eye. The primary lobes of the submaxillary gland are much larger than those of the parotid, and the lobules SALIVARY GLANDS OF MAMMALS. 407 Sublingual glands, Humaii, uat. size, c.xxv". have an irregularly triangular arrangement. The arteries and veins that supply the submaxillary gland, are derived from the facial and lingual. The nerves are from the mylo-hyoid branch of the dental, and the gus- tatory, but chiefly from the submaxillary ganglion. The sublingual gland forms a distinct eminence underneath the anterior part of the tongue by the side of the fraenmn. Its shape and position are shown in fig. 305, c, c : its lobules are smaller, firmer, and more distinct than those of either the parotid or max- illary : its ducts are nume- rous, their orifices conspi- cuous along the ridge of mucous membrane behind the terminal papilla of the duct of the submaxillary. Occasionally one duct is longer and larger than the rest : it is named, after the anatomist who first drew attention to it, ( Bartholin's duct,' fig. 306, a. For a like reason, Anthropotomy calls the duct of the submaxillary, ib. I, 6 TTharton's,' that of the parotid ' Steno's,' and the short ducts of the sublino-ual ( Rivinus's.' The secretion of the latter gland is ~ o more viscid than true saliva : and it may be considered as the best defined of the subsidiary glands of the salivary system. The posterior part of the sublingual is occasionally represented by one or more distinct glands in juxtaposition, each furnished with a very short excretory duct. The anterior lingual glands, fig. 307,5, are situate below the apex of the tongue, between the lower longi- tudinal and transverse muscular fibres, and emit their secretion during the movements of that organ upon the mucous membrane beneath the tip, by delicate ducts indicated by bristles in the figure. The labial glands form a series of closely packed small, dense, spheroidal crypts, situated in the areolar tissue between the mucous membrane of the mouth and the orbicularis oris muscle ; their excretory ducts open upon the posterior or free surface of the labial mucous membrane. They are not visible to the eye when the lips are in their natural lax position, but when the latter are everted, they appear as prominences upon the tense mucous membrane. 408 ANATOMY OF VERTEBRATES. The buccal arc smaller than the labial glands, but resemble them in form and position, being irregularly spheroidal, and placed between the buccinator and mucous membrane ; they open by the orifices of distinct ducts upon the free surface of the latter. The molar glands are placed between the buccinator and masseter muscles. They are larger and more dense than the buccal, being composed of several lobes. The ducts open upon the mucous membrane at the posterior part of the cheek. The pala- tine glands are very numerous and small, and situated partly between the mucous membrane and the palatine arch, and partly between the mucous and muscular layers of the soft palate. The former are situated on either side of the median line, and form a thick layer, being more closely aggregated together in the front and behind than in the middle, opening on to the mucous membrane by distinct orifices. The latter, smaller than the former, exist both on the upper and lower surface of the velum, and are continuous below, where they are more numerous than above, with the glands of the hard palate. The aggregate follicles opening near the fossulate papillae at the back part of the tongue are sometimes specified as the ( posterior lingual glands.' Like the other subsidiary glands their secretion is more mucous and lubricating than solvent : and the homologues of most of these glands are maximised in herbivorous Mammals in relation to the movements and mastication of their coarse vegetable food. The diversion of the paro- tid secretion from the mouth of a horse, during mastica- tion of oats, was followed by dryness of the interior of the bolus and an exte- rior envelope of tenacious mucus, which was as abundant as be- fore the division of Steno's ducts ; the experiment } indicating that the secretion of the parotid is of the more fluid saliva which moistens, in ordinary mastication, the whole mass ; and that the sub- maxillary and sublingual, like the more diffused tributary glands, provide the secretion of the slimy lubricating saliva. Further experiments showed 2 that the flows from the parotid, sub- maxillary and sublingual glands are respectively regulated by conditions special to each. Thus, the quantity of saliva secreted Anterior lingual gland, Human, nat. size. cxxv". 1 cxxvi". Ib. SALIVARY GLANDS OF MAMMALS. 409 by the parotid of a horse is in direct ratio to the dryness of the food and the difficulty experienced in its mechanical division. The mastication of straw and hay causes a greater flow than does that of oats and farinaceous matters ; the mastication of moist forms of food hardly excites any. The saliva from the sublingual and submaxillary ducts flows nearly in equal abundance whether mastication be exerted on dry or moist forms of food ; and, owing to its comparative tenacity, it is not easily imbibed into the centre of the masticated material, but is gathered round the surface of the mass, thus favouring its passage along the alimentary canal. The comparative anatomy of the salivary system supports the conclusions of experimental physiology : thus, the parotids are re- latively largest in mammals that masticate most; the submaxil- laries are largest in those that need the greatest amount of viscid lubricating secretion. In the anteaters, hairy or spiny, the parotid is so small as to have escaped the notice of Cuvier and his continuators : * the submaxillary attains its maximum of size. In many long-tongued Edentates (Myrmecophaga and Dasyjms) a bladder is superadded to the submaxillary gland both for storage of a quantity of secretion needed in a sudden excess of outflow, and also for adding to the tenacity of the secretion so poured out to lubricate the tongue. In Echidna the end is gained by sub- division with enlargement of Wharton's ducts. Most analyses of saliva have been made on that from the human mouth which is the combination of the secretions of the various glands above described. The peculiar animal principle called 6 ptyalin' is a nearly solid matter, adhesive, of a yellowish colour : it is neither acid nor alkaline, is readily soluble in ether, alcohol, and essential oils, but more sparingly soluble in water. It appears to give the peculiar odour to saliva : when pure it may be kept long at a moderate temperature without undergoing decomposition. Dr. Wright's analysis of human saliva 2 is as follows :- Water 988' 1 Ptyalin .... Fatty acid Chlorides of potassium and sodium Albumen combined with soda Phosphate of lime Albuminate of soda . Lactates of potash and soda Sulphocyanide of potassium Soda .... Mucus, with some ptyalin . 1-8 5 1-4 9 6 8 7 9 5 2-6 1 ' Lorsqu'il n'y a point de parotides, comme cela a lieu dans Tcchidne et le fov.rmi- lier, la proportion des maxillaires augmente considerablement.' xn. vol. iv. p. 421. 2 cxx". p. 417. 410 ANATOMY OF VERTEBRATES . 308 Pure saliva obtained from the parotids and submaxillaries of a dog, and from the parotids of a horse, is incompetent to effect the saccharine transformation of starch : but the secretion of the mucous and subsidiary glands of the mouth reacts upon either starch or sugar in the way of producing lactic acid. 2'25. Alimentary canal, Lijcncephala. - - In the Ornitho- rhyurlius the oesophagus becomes slightly dilated near the dia- phragm, extends a little way into the abdomen, and expands into a moderate-sized membranous stomach, fig. 308, t, which is chiefly remarkable for the close approximation of the cardiac and pyloric orifices. The intestinal canal is moderately wide, five feet three inches and a half in length, and provided, at a distance of four feet three inches from the pylorus, with a small and slen- der cascurn, ib. w. The small intestines are chiefly remarkable for the extent of the mucous coat, which is disposed in nume- rous folds or valvulaa conniventes: these are transverse at the be- ffinninff of the duodenum, but are O O placed more or less obliquely in the rest of the small intestine ; they are about two lines broad, are close together in the duode- o but diminish in breadth num. and number as they approach the crecum coli. There are about fifteen longitudinal folds in the o first half of the colon ; the re- mainder of the intestine has a smooth inner surface. There is 110 valvula coli. The rectum, ib. z, terminates at the anterior and dorsal part of the vestibular Thoracic and abdominal viscera, Ornitliorhynchus. Compartment 01 tllC Cloaca. As the food undergoes less comminution in the mouth of the Echidna than in that of the Ornithorhynchus, the pharynx and oesophagus arc wider, and a ALIMENTARY CANAL OE MARSUPIALIA. 41] dense epithelium lines the inner surface of the latter tube : it is continued over the capacious stomach to the pylorus, near which orifice it is developed into numerous horny and sharp papillae. The subjacent mucous membrane is smooth ; the tunics of the stomach are thin, to near the pylorus, where the muscular coat assumes something of the gizzard-character, and the inner coat forms a pro- minent protuberance in the duodenum. The intestinal canal of the Echidna is seven times the length of the body; the mucous membrane is not raised into valvular folds ; a small vermiform and glandular caecum divides the small from the large intestines; the rectum terminates as in the Ornithorhynchus. The various modes of locomotion, resulting from the different ' O modifications of the osseous and muscular systems observable in the several families of Marsupialia, relate to the acquisition of as various kinds of alimentary substances, which necessarily re- quire for their assimilation as many adaptations of the digestive organs. Food means of obtaining it- -instruments for preparing and mechanically dividing it cavities, canals, and glands for chemically reducing and animalising it form a closely connected chain of relationships and interdependencies. The preparatory instruments have been described in previous sections. In all Marsupials the oesophagus in passing through the chest recedes from the spine as it approaches the diaphragm, and is loosely connected with the bodies of the dorsal vertebras by a broad duplicature of the posterior mediastinum. In the Phalangers the oesophagus terminates in the stomach almost as soon as it has pierced the diaphragm ; in the Opossums it is continued some way into the abdomen ; in the Didelpliys virginiana, for example, for the extent of an inch and a half; in Did. brachyura, for half an inch. In the Kangaroos the abdominal portion of the oesophagus is of still greater extent ; I have observed it five inches long in a male Macropus major. The inner surface of the oesophagus is generally smooth, or dis- posed in fine longitudinal plaits ; but in the Virginian Opossum the terminal part of the oesophagus presents many transverse folds of the lining membrane analogous to, but relatively larger than, those in the Lion and other Felines. I have not met with a like structure in the Phalangers, nor in any other genus of Marsupials; what is more remarkable is that the transverse cesophageal rugae are not developed in the carnivorous Dasyures or Phascogales, where analogy would lead one to expect them, rather than in the insectivorous Opossums. The stomach presents three leading modifications of structure 412 ANATOMY OF VERTEBRATES. 309 in the Marsupialia ; it is either simple, as in the Zoophagous, Entomophagous, and Carpophagous tribes ; or is provided with a cardiac glandular apparatus, as in the Koala and Wombat ; or is complicated by sacculi, as in the Poephagans. It might have been expected that the stomach would have ex- hibited some modifications in the development of the left or cardiac extremity corresponding with the differences of food and dentition observable in the large proportion of the Marsupial order, in which this viscus presents its simple condition ; but this is not the case : the form of the stomach is essentially the same in the carnivorous Dasyure, the insectivorous Bandicoot, and the leaf-eating Phalangers, It presents a full, round, ovate, or sub- triangular figure, with the right extremity projecting beyond and below the pylorus ; the longitudinal diameter seldom exceeds the vertical or transverse by more than one-third ; often, as in Plias- cogale and Dasyurus viverrinus, by only one-fourth of its own ex- tent ; and the oesophagus enters at the middle of the lesser curvature, or sometimes nearer the pylorus, but always leaves a large hemi- spherical cul-de-sac on the left side. Daubenton 1 has given illus- trations of this characteristic form of the stomach in different species of Didelphys ; it is here figured as it exists in the PJiascogale, fig. 309. The stomach is relatively much more capacious in the carnivorous Marsupials than in the carnivorous Placentals. Some slight modifica- o tions occur in the disposition of the lining membrane ; in the Phasco- gcde a series of very thick rugre radiate from the middle of the upper part of the cascal end of the stomach, some of which were con- tinued alono; the lesser curvature Alimentary canal, Phascogale fla\Mpes. to the pylorus. In the Perameles nasuta the internal surface of the left cul-de-sac is smooth ; the right half of the stomach has rugae, running chiefly in a longitu- dinal direction, and particularly numerous towards the pylorus. 1 CXXll". lulll. X, \t\. 48, fig. 1. ALIMENTARY CANAL OF MAESUPIALIA. 413 310 The stomach in the Wombat and Koala does not materially differ in external figure from that of the above-cited Marsupials ; the resophagus terminates nearly midway between the right and left extremities, but further from the pylorus in the Wombat than in the Koala. The conglomerate gastric gland is of a flat- tened ovate form, relatively larger in the Wombat than o in the Koala, situated to the left of the cardiac orifice, at the lesser curvature of the stomach, fig. 310. The gas- tric gland has a similar position in the Beaver, but in this animal the excretory orifices of the gland are ar- ranged in Stomach of the Wombat, inverted. 311 three longitu- dinal rows, while in the Wombat and Koala they are scattered irregularly ; in the Wombat they are about thirty in number, and the bottoms of the larger depressions are subdivided into smaller cells. In the partially contracted state the inner membrane of the stomach of the Wombat is dis- posed in longitudinal rugje, which gradually subside to- wards the pylorus ; but when the stomach is dis- tended these folds disap- pear, and the left extremity presents a full globular form. The sacculated stomach of the Kangaroo, which offers the extreme modifica- tion of this organ in the Marsupial order, resembles the human colon both in its longitudinal extent, structure, and disposition in the abdomen. In a full-grown female Kangaroo (Macropus major) I found the abdominal oesophagus, fig. 311, , four inches long, and ter- minating at six inches distance from the left extremity of the stomach : this was folded forward and to the right in front of the oesophagus ; from the basis of the left cul-de-sac the stomach continued to expand, and descended into the left lumbar and ff Stomach of the Kangaroo. 414 ANATOMY OF VERTEBRATES, iliac regions, whence it stretched upward and to the right side obliquely across the abdomen, to the right hypochondrium, where it became contracted and finally bent downward and backward to terminate in the duodenum. The whole length of the stomach, following its curvatures, was three feet six inches, equalling that of the animal itself from the muzzle to the vent. The cavity may be regarded as consisting of a left, a middle, and a right or pyloric division. The left extremity of the stomach is bifid, and terminates in two round cul-de-sacs. The sacculi of the stomach are produced, like those of the colon, by three narrow longitudinal bands of muscular fibres, which gradu- ally disappear, together with the sacculi at the pyloric division. One of the longitudinal bands runs along the greater curvature, at the line of attachment of the gastro-colic omen turn ; the others commence at the base of the left terminal pouches, and run, one along the anterior, the other along the posterior side of the sto- mach : the interspace, between these bands, forming the lesser curvature of the stomach, is not sacculated. The largest of the two terminal sacculi, d, fig. 310, is lined with an insulated patch of vascular mucous membrane, which is continued for the extent of five inches into the cardiac cavity ; the thick epithelium is continued from the oesophagus in one direction into the nearest and smallest sacculus, c, and extends in a sharp- pointed form for a considerable distance in the opposite direction into a series of sacculi in the middle compartment of the stomach, ib. e : this epithelium is quite smooth. The vascular mucous surface re- commences by a point at the great curvature, near the beginning of the middle compartment, and gradually expands until it forms the lining of the whole inner surface of the rio;ht half of the c3 o stomach. Three rows of clusters of mucous follicles, ib. g, g, are developed in the mucous membrane of the pyloric half of the middle compartment; they are placed parallel with the longi- tudinal muscular bands : about fifteen patches are situated along the greater curvature, and there are nine in each of the anterior o ' and posterior rows. These glandular patches disappear alto- gether in the pyloric compartment of the stomach, where the lining membrane is thickened, and finely corrugated ; but imme- diately beyond the pylorus there is a circular mucous gland three-fourths of an inch broad : the non-sacculated pyloric divi- sion of the stomach was five inches in length. In the smaller species of Kangaroo the stomach is less compli- cated than in the Macropus major; the number of sacculi is fewer : in Macropus parryi, e. g., the third longitudinal band at the great curvature of the stomach is almost obsolete : in the ALIMENTARY CANAL OF MAESUPIALIA. 415 Brush-tailed or Rock Kangaroo (Macropus penicillatus) the car- diac extremity terminates in a single subclavate cul-de-sac : the oesophagus opens into the middle division of the stomach, close to the produced crescentic fold which separates it from the cardiac compartment. In the great Kangaroo a second slighter fold is continued from the right side of the cardiac orifice parallel with the preceding, and forming with it a canal, somewhat analogous to that in the true ruminating stomachs, and along which fluids, or solid food not requiring previous preparation in the cardiac cavity, might be conducted into the middle compartment. I have more than once observed the act of rumination in the Kangaroos kept in the vivarium of the Zoological Society. It does not take place while they are recumbent, but when the animal is erect upon the tripod of the hind legs and tail. The abdominal muscles are in violent action for a few seconds, the head is then a little depressed, and the cud is masticated by a rapid rotatory motion of the jaws. This act is by no means re- peated in the Kangaroos with the same frequency or regularity as in the true Ruminants. A fact may, however, be noticed as an additional analogy between them ; balls of hair, cemented by mucus, adpressed and arranged in the same direction, are occa- sionally formed in the stomach, of which I have met with two, of an oval shape, in the Macropus parryi. In the genus Hypsiprymnus the stomach is as singularly com- plicated as in the Kangaroos, and the complication is essentially the same in both ; arising from the sacculation of the parietes of a very long canal by a partial disposition of shorter bands of longitudinal fibres ; but in the Potoroos this sacculation is con- o ' fined to that part of the stomach which lies to the left of the oesophagus, while the right division of the cavity has the ordinary form and structure of the pyloric moiety of a simple stomach. The left or cardiac division is enormously developed ; in relative proportion, indeed, it is surpassed only by the true ruminant stomachs, in which both the rumen and reticulum are expansions of the corresponding or cardiac moiety of the stomach. The re- lation of the stomach of a Potoroo to that of a Kangaroo may be concisely expressed by stating that the termination of the oeso- phagus in the former is removed from the commencement, or left, of the middle sacculated compartment to its termination. When fluid is injected into the stomach of a dead Potoroo, it distends first the pyloric division ; it is probably by a kind of antiperistaltic action that the aliment is propelled into the long sacculated cascum to the left of the oesophagus. Having seen that, with the exception of the Potoroos and Kan- 416 ANATOMY OF VERTEBRATES. garoos, the stomach is simple in the Marsupialia, presenting only some additional mucous glands in the Koala and Wombat, it is to the succeeding parts of the alimentary canal that we have to look for those modifications which should correspond with a vege- table, a mixed, or an animal diet ; and never perhaps was a physiological problem more clearly illustrated by comparative anatomy than is the use of the ca3cum coli by the varying con- ditions which it presents in the present group of Mammalia. In the most purely carnivorous group of the Marsupial order the stomach presents in the magnitude of the left cul-de-sac a structure better adapted for the retention of food than we find in the stomachs of the corresponding group in the placental series. In the most strictly carnivorous Ferce, as the cat-tribe, there is a caecum, though it is simple and short ; but in the Marsupial Sarcophaga 1 this part is entirely wanting, and the intestinal canal, short and wide, is continued, like the intestine of a reptile, along the margin of a single and simple mesentery from the pylorus to the rectum. The jejunum, in the Thylacine, has a diameter of two inches and a half. In the entomophagous 1 Marsupials, some of which are suspected with reason to have a mixed diet, the intestinal canal is relatively longer ; the distinction of small and large intestine is established ; and the latter division commences with a simple, moderate-sized, subclavate cascum, fig. 312. In the carpophagous 1 Phalangers, whose stomach resembles that of the predatory Dasyure, the compensation is made by a longer intestine, but principally by the extraordinary length of the caecum, which in some species is twice that of the body itself. 312 313 314 Crccum of the Opossum. Lastly, in the Koala, which is, perhaps, a more strictly vegetable feeder than the Petaurists or Phalano;ers, the crccum, O ' * fig. 313, is more than three times the length of the animal, and its essential part, 1 LXXIV' and LXXX', p. 330. CsBcum of the Kaola. Caecum of the Kangaroo. ALIMENTARY CANAL OF MARSUPIALIA. 417 the inner secreting membrane, is further augmented by about a dozen longitudinal parallel, or nearly parallel, plaits, which are continued from the colon three-fourths of the way towards the blind extremity. When we reflect that the Sloth, which has the same diet and corresponding habits with the Koala, has a singularly complicated stomach, but no caecum, the vicarious office of this lower blind production of the digestive tube as a subsidiary stomach is still more strikingly exemplified. In the Marsupials Avith sacculated stomachs the caecum coli is comparatively short and simple. In the Potoroos, which scratch up the soil in search of larvae and farinaceous roots, it is shorter than in the great Kangaroos which browze on grass. There is a slight tendency to sacculation at the commencement of the crecum in the latter Mar- supials, by the development of two longitudinal ca?cum of the bands, fio- 314. In the Wombat the caecum is ' ~ extremely short, but wide ; it is remarkable for being provided with a vermiform appendage, fig. 315. In this animal, how- ever, the colon is relatively longer, larger, and it is puckered up into sacculi by two broad longitudinal bands. In the speci- men dissected by me, one of these sacculi was so much longer than the rest as to almost merit special notice as a second caecum. The most interesting peculiarity which the Zoophagous Mar- supials exhibit in the disposition of their simple intestinal canal, consists in its being suspended from the very commencement of the duodenum on a simple and continuous mesentery, like the intestine of a carnivorous reptile. The duodenum makes the ordinary fold on the right side, but it is not tied to the spine at its termination; the commencement of the jejunum may, however, be distinguished by a slight twist of the mesentery, and a fold of peritoneum is continued from the lowest curve of the loop of the duodenum to the right iliac region, as in the Kangaroos. The intestine is a little narrower at its middle part than at its two extremes ; the tunics increase in thickness towards the rectum. There is a zone of glands at the commencement of the duodenum. In the Entomophagans ! the duodenum is tightly connected to the spine, where it crosses to be continued into the jejunum : from this part the mesentery is continued uninterruptedly along the small intestines and colon to the rectum ; so that although the caecum is generally found on the right side, its connections are sufficiently loose to admit of a change of position. In the Carpo- 1 See LXXIV', for characters of these families of Marsupialift. VOL. III. E E 418 ANATOMY OF VERTEBRATES. phagana l the pygmy Petaurist (Acrobates) shows the duodenum attached to the spine as in the opossums, but it is not tied down to the right iliac region by a fold of peritoneum continued from the convexity of its depending curve. The caecum is dis- posed in a spiral curve in the left lumbar region ; the colon ascends a little way in front of the stomach, receiving a branch of the superior mesenteric artery, and is then continued straight down to the anus ; again exemplifying the oviparous character by the shortness of the large intestine. In the Pet. tuyuanoides the duodenum is tied down to the iliac region, as in the Dasyure ; the caecum is four inches long, and the colon is relatively longer than in Acrobates ; it makes the tour of the abdomen much as in Man, but is continued into the rectum without forming a sigmoid flexure. In the Phalano-ers the duodenum winds round the root ^3 of the mesentery, descending pretty low down on the right side, and becoming a loose intestine or jejunum on the left side. The long cajcum is suspended by a broad duplicature of peritoneum continued from the mesocolon ; and the colon is closely attached at its transverse arch to the duodenum and root of the mesenterv. / In the Koala the caecum and large intestines arrive at their O maximum of development. The duodenum commences with a small pyriform sacculus nearly an inch in breadth, and soon contracts to a diameter of five lines, which is the general calibre O of the small intestines. The large intestines, where the ileum terminates, have a diameter of two inches. The end of the ileum, fig. 316, , protrudes for the extent of a quarter of an inch within the caecum, forming a very effectual valve : near this part there are two wide and deep glandular fossae : the longitudinal valvulre conniventes of the large intestines have already been noticed. In the Potoroos the small intestines are disposed nearly as in the Phalangers : the short and wide caecum lies in the right o o hypogastrium : the colon makes the usual tour of the abdomen, but is disposed in long convolutions through its whole course, 316 Ileo-csecal valve, Koala. Half its natural size. ALIMENTARY CANAL OF MAKSUPIALIA. 419 being suspended on a broad mesocolon. The diameter of both small and large intestines is nearly the same : in Hyps, setosus I found this to be half-an-inch. In the great Kangaroo the descending portion of the duodenum is attached posteriorly, by means of a thin peritoneal duplicature, to the spine, and anteriorly to the ascending colon : it makes an abrupt turn upon itself, and a fold of peritoneum is continued from the convexity of the curve to the right iliac region. The small intestines are strung in short folds on a rather narrow me- sentery. The caecum is in part suspended from the same me- senteric fold. The colon, besides its posterior connections with a mesocolon, is attached, as before observed, to the duodenum ; and also, by means of the great omentum, pretty closely to the stomach, whence it passes down, forming many large and loose convolutions, to the rectum, being attached by a broad mesocolon to the left hypochondriac region. The zone of glands at the commencement of the duodenum has been already noticed ; they are present in other Marsupials, even in the most carnivorous species. The villi of the small intestines in the Kangaroo are of moderate length, compressed and close- se't. Grlandulae aggregate are arranged in narrow patches in the ileum. There are seven groups of similar follicles in the caecum ; and a few long and narrow patches of glands occur in the colon intermingled with numerous glanduloe solitariaa ; the surface of the rest of the lining membrane of the large intestine is disposed in a very fine net-work. Two faint longitudinal bands extend along the first ten inches of the colon and are continued along two-thirds of the caecum : the sacculi produced by these bands are but very feebly marked. The contents of the caecum in the great Kangaroo are of a pultaceous consistence, and the mass continues undivided along the first two feet of the colon, gradually becoming less fluid and then beginning to be separated into cubical faeces about an inch square. The diameter of the large intestine in this species ex- ceeds very little that of the small intestines. In all the Marsupials two sebaceous follicles open into the termination of the rectum. The anus has its proper sphincter, but is also surrounded, in common with the genital outlet, by a larger one. TVheii the penis is retracted, the faecal, urinary, and o-eiiital canals all terminate within a common external o outlet ; so that in the literal sense the Marsupials are monotre- matous. The following is a table of the length of the intestinal canal, E E 2 4i>0 ANATOMY OF VERTEBRATES. and its parts, as compared with the body, in a lew species of the different families of Marsupialia :- SPECIES. Motly from snout to vent. Intc.-l in:il canal with caecum. Small intestines. I, urge intestines. Caecum. Thylacinus Harrisii . . Phascogalc Jlavipcs . . . Dasi/nrus -macrurus P< ramelcs nasuta Didilplit/s PJiilitiHlt r . . Petaurus -pygmaus . . Phahtngista vulpina . . Ditto ft. inch. 3 4 5 1 4 1 4 9 2i 1 S~ 1 7 ft. inch. 9 8 14 5 3 5 3 5 6$ 24 10' 18 8 ft. inch. 2 5 1 11 5 11 9 9 ft. inch. 9 1 2* 0| 9 6 10 ft. inch. 3 4 1 4 10 2 1 Phascolarctos fuscus Hijpsiprymnus setosus . . Macropus major Phascolomys Vombatus 1 11 1 3 3 2 6 24 5 32 25 6 7 8 2 5 22 11 3 10 5 2 6 9 14 2 6 5 2 1 8 1 317 226. Alimentary canal of Rodentia. In relation to the de- gree of comminution of the food and in continua- tion of the character of the fauces the oesophagus is narrow in all Rodents and is usually continued a short way into the abdo- men before opening into the stomach. The posi- tion of the cardia is at or near to the middle of the upper curvature (fig. 317, /, Rat, fig. 318, /,/, Vole) as in Marsupials, and the modifications of the ali- mentary canal in relation to the nature of the food are, also, manifested chiefly in the caecum. The left end of the stomach com- monly projects beyond the pylorus, fig. 317, d, fig. 318, I) : and it is not unusual to find both 'blind sacs ' marked off by transverse constrictions from the mid-part of the cavity, fig. 317, I. The cesophageal epithelium is usually continued upon the inner surface of the cardiac compartment, ib. a. In the Porcupine, which shows well this tripartite type of stomach, Intestinal canal, \\iih proper and supplementary stomachs (Mas Itatttis). cxxii'. ALIMENTARY CANAL OF KODENTIA. 421 the pyloric aperture is much larger than the cardiac one and is bounded toward the left side by a valvular ridge. In the Squirrels (Sciurus) the stomach is of a pyriform or oval shape, quickly contracting to a conical or cylindrical por- tion, which is bent upon the small curve and terminates in the pylorus. The cardiac compartment, which projects far to left beyond the oesophagus, is lined with a thick epidermis, which forms two oval lips, as it is prolonged around the opening into the second compartment, the lining membrane of which is gastro- mucous. In the Hamsters (Cricetus) the stomach is divided into two pouches, separated by a deep constriction ; the left pouch is cylindrical, the right globular. The cardiac orifice is situated in the constriction, so that food can pass at once into the pyloric compartment and be antiperistaltically moved and stored in the cardiac division. In the Rat (Mus decumanus) the abdominal part of the gullet, fig. 317,/, is 1^ inches long, and carries forward a fold of peri- toneum. The cardiac compartment, ib. a, has thin coats and is lined by an epithelium which usually gives it a whiter colour than the rest of the organ. At the midpart, ib. b, there is a tendinous 318 319 Stomach of tlie Water-vole, cxxn'. Stomadi of the Lemming, inner surface. cxxxm". patch from which muscular fibres radiate, as in the bird's stomach : the muscular coats of the pyloric division, d, are thicker, as is also the gastro-vascular lining membrane. In the Water-vole (Arvicola amphibius) the cardiac and middle compartments form one elongated cavity, fig. 318, a, f, sepa- rated by a constriction from the pyloric portion, b. This swells out in two directions, above into a small sacculus, e, the coats of which are thin, like those of /, and below into the true digestive pyloric part, with a thicker muscular tunic and gastro-vascular lining membrane. The epithelial lining of a, f, terminates by a 422 ANATOMY OF VERTEBRATES. fringed margin. The Lemmings have a similar type of stomach, complicated with a slight subdivision, fig. 319, c, of the right com- partment, near the pylorus, where the thicker glandular lining graduates into the thin smooth mucous membrane of the supra- pyloric sac, e. From the cardiac orifice a pair of ridges curve toward the pyloric division, defining a groove or canal, f, ana- logous to that which will be shown in the Ruminants ; the border of the epithelium of the cardiac half is well-defined and some- times fringed. The gastric tubes of the compartment, /;, are so complex as to give the character of a gland to the lining mem- brane. In the Beaver ( Castor) the stomach is transverse and elongated in that direction, the right portion being larger than that which is situated to the left of the cardia ; the oesophagus is inserted into the first third of its anterior margin by a narrow opening, surrounded with pointed processes, which are analogous to the fringes formed by the epithelium in many other Rodents. On the right of the oesophagus, at the lesser curvature of the stomach, is a gastric gland composed of numerous branched follicles, the blind ends of which, when exposed by removal of the muscular coat, give the gland a tabulated surface : the orifices of the glands are arranged on slight ridges in three longitudinal rows on a flat tract of the inner surface. On the right of these orifices com- mences the pyloric portion, the termination of which is indicated by an external constriction, and by an internal thickened ring : the pylorus is approximated to the cardiac orifice. This pyloric portion, which is more muscular than the rest, is sometimes dilated into a distinct pouch, separated by a constriction from the pyloric cul-de-sac. The internal membrane presents everywhere the same appearance, except that in the pyloric portion it appears to be more smooth, and its folds take a different direction. On the right of the cardia there is a very thick fold, separating the left from the right compartment. In the Dormouse (Mi/ozus ylis) and Muscardine (M. avellanarius) similar follicular glands are aggregated round a dilated termination of the oesophagus, or cardiac commencement of the stomach, like the ( proventriculus ' of birds. 1 We have here a repetition of the structure noted in the Wombat. In the Cape Mole (IBctthyergus) the abdominal oesophagus is an inch in length and terminates midway between the two ends of the stomach. The right compartment is of enormous size, elongated and pierced at its base by the cardiac orifice ; the left 1 xx. vol. i. p. 181, No. 590 A. ALIMENTARY CANAL OF KODEXTIA. 423 compartment is of smaller dimensions, of a globular form, and separated from the preceding, both by an external constriction and an internal fold of the mucous membrane. There are, more- over, two additional folds nearer to the pylorus, which seem to form a third compartment. The Oryctere ( Ori/cterus) has its stomach slightly different : its position is more longitudinal, so that the left compartment is anterior, and the right posterior ; the pyloric portion is short, cylindrical, and directed forward. In Capromys Fournieri the oesophagus, after a short course in the abdomen, terminates in a stomach six inches long, about 2^ inches from the left end : a pouch of the same extent is con- tinued from the right of the pylorus, which is situated 1 J inches to the rio;ht of the cardia. ~ In the Coypu (Myopotamus) the stomach closely resembles that of Capromys., being of an oblong figure, both extremities having pretty nearly the same volume ; the cardiac extremity projects three inches beyond the entrance of the narrow ceso- phagus, and the pyloric sacculus, a little more than two beyond the pyloric orifice. The stomach, measured in a straight line from end to end, is 7J inches ; its greatest depth 4-J inches. In the Agouti (Dasi/procta agouti), with a stomach 5J inches long, the constriction dividing it into cardiac and pyloric por- tions is deep : the latter bulges out on each side the pylorus so as to make the duodenum commence from a central depres- sion. The Paca ( Coelogenys) shows the same structure. In an Acouchi the gastric constriction was not present or had relaxed. In the Capybara the abdominal oesophagus is two inches in extent : the greater curvature of the stomach is sometimes found puckered into sacculi by contraction of a band of longitudinal fibres. In the Rabbit and Hare (Lepus, Lin.) the stomach is roundish, bent in a quick curve, with the oesophagus entering nearer the left or great end than the pyloric end : the left end adheres to part of the abdominal oesophagus : it is usually found partially constricted into two compartments, the pyloric being the thickest and most muscular. The sides of this division have a well-marked tendinous patch. The intestinal canal usually, in Rodents, begins by a well-marked dilatation, and the whole duodenum is more continuously and loosely suspended than in most higher Mammals. In the Dormice {Myoxus) which hybernate like the bear, there is no ca3cum. In the common Mouse and Rat (Mus, fig. 317) the crecum, k, /, is short, wide, and bent ; the colon, />, reduced to the calibre of the ileum, leaves the ca3cum, like the duodenum quitting the stomach. The 424 ANATOMY OF VERTEBRATES. 320 fa-ces begin to be divided in the colon, by constrictions of the gut, as in the figure : the rectum runs some way along the base of the tail before terminating. The small intestines are five times the o leno-th of the bodv, the large intestines once that length. In O / ' O O the Mole-rat (Bathyeryus) the ca3cum makes a close spiral turn, and its inner membrane is augmented by many trans- verse folds. The caecum is of greater length in the Sciuridce : in the common Squirrel it is curved, fig. 320, c, and divided from the colon, (l i/tex] there is a more marked constriction between the appendix and the ciucum. The colon is sacculated and mo- derately long in all Catarhines : it is loosely suspended by a broad mesocolon, and only in tailless apes does the crecum begin to adhere, through an incomplete peritoneal investment, to the right hypogastric region. 330. Alimentary canal of Bimana.- -The chief characters of the canal in this order are the termination of the gullet almost as soon as it has entered the ab- domen ; the more extensive and closer adhesion of parts of the alimentary canal, as the duodenum, caecum, beginning and end of colon, to the abdo- minal walls, which relates to the erect posture ; the more definite and finished character of the several parts of the canal ; and the modification of the lining membrane of the small intestines, called ' valvulas con- niventes, ' for a more com- plete and efficient extraction of nutritious matter from the chyme. The stomach presents a greater extent transversely to the abdomen than in Quadru- mana, and the blind left end (' saccus caucus,' Haller) is less extended and expanded than in Monkeys and Lemurs, the O3sophagus opening more to the left, and leaving a more extensive ( lesser curvature,' fig. 332, c, P. Anthropotomy distinguishes the ' cardiac orifice,' fig. 333,,^r ; the ' cardiac pouch ' or ' blind sac,' ib. g, d ; the 'lesser curvature,' ib. a, e, b ; the ( greater curvature,' ib. g, d,f, c, h ; the ' pyloric portion,' ib. e, b, b, c ; and its orifice or ( pylorus,' ib. b, b. In a state of moderate distension the length of the Stomach and intestina cnna of the adult Human subject. CXLVIII". ALIMENTARY CANAL OF BIMANA. 435 stomach averages from thirteen to fifteen inches; its widest diameter five inches; its capacity five pints. It extends almost transversely across the upper (in Man) part of the abdomen from the left toward the right side, the pylorus entering the region called 'right hypochondrium :' as the stomach becomes distended, it gently rotates the great curvature forward. The outer or ' serous ' coat is continued from the lesser curvature and contributes with the end of the gullet and beginning of the gut to suspend or attach the bag : from the curve d, f, c, the serous coat extends down to form the ' great omen- turn,' fig. 388 : thus provision is made for the digestive cavity to encroach upon the interspace of the two serous layers during 333 o-< >ui, Human stomacli, inverted. CXLVIII". expansion. The muscular coat of the stomach is in three layers which, from the general course of the fibres, are termed i lon- gitudinal,' ' transverse,' and ' oblique : ' the latter or innermost layer, fig. 333, //, d, f, c, is partial : the other two are com- plete. The longitudinal layer, like that of the gullet, is the outermost; and the fibres radiate from the cardia, becoming thinner as they diverge, spreading and decussating with the other fibres, and hardly traceable continuously to the pylorus, save along the lesser curvature. The transverse fibres, which lie immediately beneath the longitudinal, form a thicker and more uniform stratum: in the inverted stomach, from which the mucous membrane has been dissected, in fig. 333, they are the innermost at the pyloric end, c, e, b: at the cardiac end they are lined by the layer of ' oblique ' fibres. The transverse layer increases in thickness to the pylorus, fig. 334, the circular fibres or sphincter occupying the valvular fold of the mucous membrane, F F 2 436 ANATOMY OF VERTEBRATES. ib. p. This membrane is usually of a pale pink colour, deeper tinted at the pyloric than at the cardiac portion, and produced 334 into numerous wrinkled folds or rugae. which Longitudinal section of the pylorus. CXLVJH". are not so soon effaced, under distension, as in the quadrumanous stomach. The ' basal ' part of the membrane is areolar or cellular tissue, connecting it to the muscular coat ; it also supports the vessels and nerves, forms the cylinders of the gastric tubules, and is covered by a delicate epithelial layer of the columnar kind. The gastric tubules, fig. 337, are cylin- ders of the basal membrane, packed vertically side by side, and filled by cells : their inserted end, d, is closed : they expand slightly before reaching the free surface of the membrane, where their margins become continuous with each other, so as to form a series of low ridges, the height and width of which vary somewhat in different parts of the stomach. The length of these tubes is about T , ; V^ U f an inch at the middle of the organ, almost double that length at the pyloric portion, and half that length at the cardiac region, a difference causing the different thickness of the mucous membrane in these parts of the cavity. Their diameter is about ^^th of an inch, and is a little increased in the pyloric ones : in some of these, blind processes are continued from the inserted end ; as commonly seen in the Dog, fig. 349. Toward the outlet the tubule is occupied by ( columnar epithelial cells,' fig. 337, c : the deeper portion is filled by oval nucleate cells, attaining in some cases T ^Vo* n f an inch in diameter, ib. b. The tubules are connected together by a finely fibrous form of areolar tissue, in which their blind ends, or branches, are imbedded. The principal arteries of the stomach, derived from the ( crc- liac axis,' are the l arteria coro- naria ventriculi,' fig. 335, , which courses along the lesser curvature ; the ' gastro-duodenalis,' d, which gives off the ' arteria pylorica,' g ; the ( gastro-epiploica,' ' dextra,' e, and ( sinistra,' i. The branches of all these arteries have a tortuous course and freely inosculate ; their ramuli per- 335 Arteries of the stomach, as seen by raising it CXLVIII''. ALIMENTARY CANAL OF BIMANA. 437 forate the muscular coat and form, with the veins, an expanse of network, fig. 336, e> in the loose 337 submucous areolar tissue : the capil- laries, ib. #, penetrate the gastro-mu- cous coat, their ultimate branches, of from -j-jVo'th to T gVoth of an inch in diam., ib. d, passing vertically along or between the walls of the gastric tubes o to their outlets, where thev form a fine / superficial network, b : from this the 336 Capillaries of the gasti o-mucous membrane. CXLVIII". Gastric tubule, from the middle of the Human stomach ; magii. 140 diam. CXLVIII". veins commence, and return by the vertical canals, .">.">./. curves outward and backward to the under surface of the rio-ht lobe of the liver, and lias an entire investment of r^ peritoneum : the gnt descends along the inner border of the right kidney, where the posterior Avail is left uncovered by the peritoneum, and is attached by cellular tissue to the subjacent parts : it then crosses beloAv the pancreas, be- hind the stomach, to the left, having a partial covering of peritoneum, and only regains the entire serous coat where it emerges to form the beginning of the next part of the small intestine. This is termed ' jejunum,' fig. 332, j, from its usual emptiness, and the rest of the tube is ' ileum,' ib. I : these con- volutions are suspended upon the duplica- tnre of peritoneum called ' mesentery.' The muscular tunic of the intestine consists of an outer longitudinal and an inner transverse or o circular stratum ; both layers being some- what stronger in the duodenum. The mu- cous membrane begins, in the second portion 339 a ? comiiventes,- Human o f the duodenum. to be disposed in transverse small intestine. CXLVIII". P11 nil i IIAI lolds called by the old Anthropotonnsts ' A r alA r ula3 conniventes,' fig. 338, as tending to impede, while, at the same time, conniving at, the passage of the chyme; but, in truth, extending the surface to which the chyme adheres in the process of elimination, of the chyle : their direction at right angles to the course of peristalsis not only checks the passage but insures the admixture of the various constituents of the chyme. The alteratiA'e and absorbent surface of the small intestine is further aujj- o mented, as in most Mammals, by the minute filamentary processes which, giving the free surface a velvety cha- racter, are termed i villi.' In the mag- nified section of the intestinal tunics, "fig. 339, a are the villi, c the submu- cous areolar tissue, e transverse fibres, /longitudinal fibres of the 1 The length of the body from the vertex to the vent, not to the heel, is that which should be taken for comparison of proportionate length of the intestines in Man with those of brutes recorded in the ' Tables ' of xli, tome iv. pp. 182-208. Section of Human jrjmiuni : inayii. :>u di:tm. CXLVIII". ALIMENTARY CANAL OF BIMANA. 439 muscular coat; in fig. 341 the serous coat is marked g. In the interspaces of the villi minute pores may be seen by the aid of the lens : they are the outlets of the ( intestinal tubules,' figs. 339, 341, b. Like those of the stomach they are hollow cylinders, fig. 340, closed at the ends, e, which are buried in the areolo- 340 tf m&^ j&$ m&mvl&mv 341 m j^*=-A*afc (7 ~ i ' Intestinal tubes from the jejunum niagn. 80 diam. cxLVtn". Intestinal follicle in vertical section ; magn. 40 diam. CXLVIII". fibrous tissue: their length is about five times their width, which averages -^oth of an inch : their proper wall consists of nucleated columnar cells, , b ; their mouths d, open into the area of the gut : their contents are a clear fluid and minute granules. Each villus is covered by an epithelium of columnar cells inclosing a parenchyme, with traces of unstriped muscular fibre, the com- mencement of the lacteal absorbents, and a rich supply of .capillary vessels. From the analogy of the gastric tubules it may be concluded that the intestinal ones continue the sol- */ vent and alterative operations on the chyme. Other arrange- ments of secreting surface relate to the furnishing of lubri- cating mucus for accessory offices : these are noted as the 'follicles.' They are either l solitary,' fig. 341, i, or in groups, termed i agminate,' fig. 342, and such patches appear to be bare of villi. The size and structure of the follicles are the same under both arrangements : they are considerably larger than the intestinal tubules, fig. 341, b; the follicle, 7z, expands as it sinks into the submucous tissue, d, and its broad base is usually applied to the muscular coat, e. The follicles are filled with an albumino-mucous pulp. Fig. 342 gives a moderately magnified view of a patch of ' agminate follicles,' of which patches .about a 440 ANATOMY OF VERTKHKATES. 342 score may be found in the tract of the small intestine, situated opposite the line of attachment of the mesentery, and most nu- merous in the ileum, where the intestinal contents become less dilute : rarely are any seen in the duo- denum. Viewed with a higher power, as in fig. 343, the follicular orifice, , is surrounded by a circle of pores of the ' intestinal tubules : ' and in the inter- spaces of the clustered follicles project short obtuse conical villi, b, of so much smaller size than the ordinary ones as to make the patch appear bare. The looped capillaries of the follicle come off from vessels encircling their cap- sule. The s racemose glands,' fig. 343, c, are peculiar to the duodenum, and most numerous at its commencement Avhere they form a circular layer just beyond the pylorus. Here each gland is about T y^th of an inch in diameter. The duct at the areolo-fibrous base of the intesti- nal glands, fig. 344, a, divides and sub- divides in the thick submucous tissue, and ultimately terminates, or receives the secretion of numerous subglobular or polyhedral follicles, averaging ^-^th of an inch O A / O O o U U in diameter : these answer to what are termed the e acini ' in larger glands : the nature of their secretion has not been de- termined : it, probably, resembles the pan- Patch of agminate follicles, niagii. 5 diam. CXLVIII". 343 - -.i^iCe&e . i* kW**: *- S^j^^v^^ creatic from analogy of structure. f^\ -^^ -> -i \;^Z ^TBJ 1 - Cs V ^fe ft S^S^f^S^s The ileum terminates in the side of the portion of n beginning of the large intestine leaving a short and wide sacculated ' caecum ' from near the end of which is sent off a slender ( vermiform appendage,' lig. 332, c C. The human caecum is further characterised by its fixed position ; having only a partial covering of peritoneum, which passing off from its fore part binds it down to the 'iliacus interims' muscle to which its non-serous surface is connected by areolar tissue and fascia. The intestine, as it rises from the crccuin, is called ' colon' or 'ascending colon,' ib. A c, and continues, as it passes the right kidney and e quadrat us lumborum,' to be attached ALIMENTARY CANAL OF BIMANA. 441 344 thereto by a progressively decreasing breadth of non-serous wall: the gut then resumes a complete serous coat, which passes oft into the progressively widening duplicature of peritoneum, for- ming the ( mesocolon : ' nearing the duodenum it arches across to the left, TC, at the line between the f umbilical ' and ' epigastric ' regions of Anthropotomy : then, descending ventrad of the left kidney and i quadratus lumbo- r urn,' it becomes attached thereto by areolar tissue : it next forms the folds called ' sigmoid flexure ;' ib. s F ; and, bending to the mid line, contracts and passes as the ' rectum,' R, to the vent. Save at this terminal portion, the longitudinal fibres of the large intestine are specially ag- gregated along three nearly equidistant tracts, one of which runs along the line of attachment of the mesocolon : these ' bands ' are nearly one-half shorter than the entire 345 gut, and consequently pucker it up into sacculi. They commence at the setting on of the vermiform appendage and di- verge therefrom to their positions on the crecum and colon : at the sigmoid flexure they begin to expand and form, with added fibres, a strong continuous longitudinal stratum upon the rectum. The circular fibres, uniformly thin and feeble upon the colon, are thickened round the rectum. The human ' vermiform appendage,' fig. 345, //, is commonly from 4 to 5 inches in leno-th : its diameter is about i of an & * inch : the follicular glands are so nume- rous as to constitute sometimes a conti- nuous laver. The ileum, ib. ft, opens by , . , . *, Cs?cum and ileo-cfecal valve, a transverse slit into the inner or mesial side of the caecum, c : the opening being defended by a pair Ita.-emose gland ; Human duodenum ; rnagn. 40 diam. CXLVIII". 442 ANATOMY OF VERTEBRATES. of semilunar valvular folds, of which the lower, /, is the ' ileo- crccal,' the upper, e, the ' ileo-colic ' valve. A transverse con- striction, (I, usually marks the boundary between caecum and colon. In the apes and all lower quadrumana the ileo-cascal orifice and valve are circular. The mucous membrane of the caecum and colon is the seat of both intestinal tubules and fol- licles : the latter are chiefly pre- sent in that of the rectum, which is disposed in numerous folds. Although this gut appears straight in a front view, it fol- O lows, in Man, the curve of the pelvic cavity, through which it passes, as shown in the side view, fig. 346. The peritoneum is re- flected from its upper third, form- ing the ( recto vesical ' pouch, ib. r, v ; and the rest of the gut is section of HinnanpeuM*, snowing course of rectum. Cached by tli e ordinary areolar CXLVII1". > * tissue to the surrounding part. Anthropotoniy accordingly distinguishes, in the rectum, an upper or i oblique segment,' s, r i : a middle or ' arcuate segment,' r 2, and a ' terminal portion,' r 3 : inclosed at the end by the ' sphincter am. ?> n. 331. Alimentary canal oj Carnivora. In this group the di- gestive system is adapted, as a rule, exclusively for animal diet. The oesophagus is usually wide. The muscular fibres are arranged in an external ~ longitudinal and an internal transverse layer : but, in the Lion, a third layer of longi- tudinal fibres is applied to the inner side of the circular ones at the terminal part of the tube : they are separated from the circular fibres by loose areolar tissue ; and are closely attached to the lining membrane of the oesophagus, which they, here, pucker up into numerous narrow alternating StoniMch ui' the Lion. ALIMENTARY CANAL OF CARNIVORA. 443 transverse rugae. The stomach of the Lion, fig. 347, shows its common form in the order : it is chiefly elongated from right */ c? cu to left : but lies less transversely to the abdomen than in Man : the tf cardia, , and pylorus, b, are wide apart: there is but a small extent of ( blind sac,' d, to the left of the cardia, and the pyloric end, e, b, is bent abruptly and closely upon the middle of the stomach. The longitudinal fibres of the muscular coat form a o strong band along the lesser curvature : the rugae of the inner coat affect a longitudinal course : the pyloric valve is less promi- nent than in man. The branches from the f arteria coronaria ventriculi ' pass some way down the front wall before penetrating the gastric coats ; not entering at the lesser curvature, as in Man. In all Fdid(s the pylorus is suspended by a duplicature of peri- toneum, and the duodenum has the same loose attachment, to its termination, which becomes more closely tied to the vertebral body. V tf The mesentery again expands to suspend the rest of the small in- testines. In a full grown Lion these measured 18 feet, with a uni- form circumference of 2J inches. The caecum was 2 inches long: it is simple and conical, fig. 348 : the 348 length of the large intestines was 2 feet 10 inches; the colon soon gains a circum- ference of 4 inches. The muscular coat of the intestines is thick throughout. The terminal orifice of the ileum is circular, and situated on a valvular prominence of the same form. The apex of the caecum , ^ . . i p 1 1 i Caecum of the Lion is a cluster ot intestinal tollicles. The lining membrane of the small intestine has fine and close- o set villi in the Lion ; they are longer and coarser in the Bear, and seem to be rather flattened than cylindrical. In contracted parts of the tube the lining membrane is thrown into longitudinal ~ t5 rugae : the agminate follicles form long longitudinal tracts in the Lion. In the Hyaena the caecum is about twice the length of that J O in the Lion, relatively. In the Dog the gullet extends about two inches beyond the diaphragm before terminating in the stomach. The duodenum is loosely suspended by a mesentery, except at its transit across the vertebra? to become jejunum. The caecum is relatively longer than in the Hyaena, and after a short course is folded or curved. The intestinal canal is longer and narrower in the Dog than in the <-> O Wolf, and the caecum in the latter is curved from its origin : it has O three coils in the Fox. The rugae of the gastric membrane are numerous and well- 444 ANATOMY OF VERTEBRATES. marked in the contracted stomach of the Dog. Microscopic in- vestigation of the gastro-mucous coat has shown the tubules to be more commonly subdivided at their blind ends than in Man. In fig. .')49, A is a tubule from the cardiac half., and B one from the pyloric portion, of a Dog's stomach : a, I the columnar epithe- 349 thelium ; c the sub-sacculate branches of the pyloric tubules. The intestinal mucous mem- brane is finely villous. Fig. 350 shows a magnified view of 350 Gastric tubules, Dog's stomach, magn. 60 diam. CXLV1II". Villus of the ilc u m of a Dog, magn. 40 diam. CXLVIII". one of the villi, b, from which the columnar epithelium, a, c, is partly detached : d, e, are columnar cells, more magnified, showing the nucleus. Some of the Civet tribe have a stomach of a fuller form. In the Suricate (Ry- zcena tetradactyla) the oeso- phagus, fig. 351, a, runs half an inch into the abdomen before ending in the stomach, about half an inch from the left end, ib, b. The epithelial lining of the gullet terminates abruptly, as in all Carnivora, at the cardiac orifice. The stomach is of a full oval Stomach, duodenum, and pancreas, Suricate J nut. size shape, maintaining much ALIMENTARY CANAL OF CARNIVOKA. 445 width to near the pyloric end,, c, which is too short to be bent. The duodenum, d, d, makes a large curve, and is a loose intestine, with a meso-duodenum which becomes shorter as it approaches the spine at the lower end of the curve : 3o2 it is continued into the jejunum before crossing the spine. The biliary and pan- creatic ducts, d, terminate about an inch from the pylorus. The length of the small intestines is 3 feet 2 inches, wi