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the pressure of the contents of the stomach, when acted upon by the powerful muscular coat, the œsophagus enters in a valvular manner, and is surrounded at its termination by a great accession of muscular fibres, forming a coat of an inch or more in thickness: the outermost of these fibres run longitudinally; the middle ones decussate each other obliquely; the innermost are circular and form a sphincter round the cardia. The diameter of the canal so surrounded is but 3 lines and its inner membrane is gathered into irregular transverse rugæ. That of the cardiac compartment is puckered up around the cardia, whence a few small irregular rugæ extend along the lesser curvature and about the constriction leading to the pyloric compartment: over the rest of the surface the membrane was not folded and was finely reticulate. At the constriction, ib. c, there is an accession of circular muscular fibres and a valvular production of the inner membrane about 3 lines broad. Immediately beyond this circular fold are the orifices of the two cæcal appendages, ib. d, d: they are relatively narrower than in the Manatee: their lining membrane is minutely rugous: there were comminuted fuci in both; their muscular coat is 1 lines thick: they are, in some Dugongs, of unequal length. The pyloric stomach, ib. b, is long and narrow, and extends a foot beyond the cæcal appendages before terminating in the pylorus, ib. g: the inner membrane presented a few rugæ: the cavity is bent upon itself, and the terminal part, g, is intestiniform, but with thick walls. The small intestines, in a half-grown Dugong, presented a length of 27 feet and a uniform diameter of 1 inch: they have a similar uniformity in the Manatee. In the Dugong the mucous membrane, beyond the pylorus, is for a few inches slightly rugous, and then becomes disposed in transverse wavy folds: at 5 inches from the pylorus the duodenum receives the biliary and pancreatic secretions on a mammillary eminence. Beyond this part the transverse rugæ are crossed by longitudinal ones, and the surface becomes sub-reticulate: this disposition extends along about 6 feet of the gut, when the transverse disposition subsides, and the longitudinal folding prevails throughout the rest of the small intestine. The muscular coat is 2 lines thick, the external longitudinal layer being about half a line. The orifices of intestinal follicles are arranged in a zig-zag line, thus ..

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the mucous surface along the side of the intestine next the mesentery, all the way to the cæcum, fig. 357. Where the ileum, ib. a, enters that cavity it is surrounded by a sphincter as thick as that at the cardia. The cæcum is conical; in my half-grown

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subject it was 6 inches long, with a basal diameter of 4 inches. The muscular coat rapidly increases toward the apex to a thickness of one inch: the inner surface is smooth, its capacity trifling as compared with the area of the

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rest of the large intestine, to which it may be said to act as a kind of heart, giving a first powerful impulse to the long column of vegetable magma' usually distending the colon. There is no constriction between this gut, c, and the cæcum, b. The parietes of the colon are thinner than those of the small intestine, the inner membrane is generally smooth. At the wider terminal part of the colon there are a few irregular folds for about an inch within the anus it is of a dark leaden colour, the pigmentum being continued so far beneath the rectal epithelium.

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The cæcum of the Manatee is bifid: and the colon at its commencement is sub-sacculate.

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§ 335. Alimentary canal of Proboscidia.-In the Elephant the stomach presents a simple exterior, but is longer than usual, with the cardiac sac much produced and conical: the lining membrane of this part is produced into twelve or fourteen broad transverse folds which do not go quite round.' The duodenum is at first loosely suspended and convolute, as in some rodents: it is more closely attached at its termination. The mucous coat of the jejunum is thrown into small irregular folds, both transverse and longitudinal. There are oblong patches of agminate follicles. The termination of the ileum projects as a conical valve into the cæcum. The longitudinal layer of muscular fibres is continued. directly from the ileum upon the cæcum: but the circular layer accompanies the valvular production of the mucous membrane, and is there thicker than on the free gut. The large cæcum is sacculated on three longitudinal bands, which are continued some way along the colon. In a young Indian Elephant, about 7 feet high at the shoulder, the following were the dimensions of the intestinal canal:

1 CCXXXVI. vol. ii. p. 171.

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§ 336. Alimentary canal of Perissodactyla.-In all this order the stomach has the ordinary simple outward form; the cæcum and large intestine are capacious and sacculate. In the Tapir' the œsophagus ends about one third from the left end of the stomach its thick epithelium is continued for the extent of 3 inches to the left of the cardia, and for that of 7 inches to the right, toward the pylorus: the rest of the stomach has a compact villous surface with a few narrow well-defined rugæ: the gastro-mucous membrane increases in thickness, through lengthening of the gastric tubules, as it nears the pylorus. The stomach of the Sumatran Tapir presents a similar disposition and proportion of the cuticular lining. The pyloric part of the stomach shows a tendinous lustre on each side. In one subject the length of the stomach in a right line, was 1 foot 8 inches. In the duodenum of the American Tapir, the mucous coat is raised into transverse folds, along an extent of gut of about 5 inches: in the rest of the small intestines it is smooth and even. In the Sumatran species the valvula conniventes are continued along a greater extent of the beginning of the small intestine, and reappear toward the cæcum. The length of this cavity is 1 foot, and its greatest breadth the same: it is honeycombed internally, and its lining membrane developes short obtuse processes. The

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Stomach of the Horse. CXXII'.

length of the small intestines in the Sumatran Tapir is 69 feet: in the American species 45 feet: the length of the large intestines in the Sumatran Tapir is 20 feet, but in the American kind only 10 feet. The comparative shortness of the intestinal canal in the American Tapir is a specific difference not explicable on any observed or known difference of food or habits.

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In all the Equide the stomach is simple, differing from that in Man by the pyloric part, fig. 358, d, being less contracted and

The species dissected were the common one (Tapirus Americanus, Gmelin), CLI". p. 161, and the Tapirus Sumatranus.

produced beyond the cardiac part: and this distinction is maintained by more important characters of internal structure. The œsophagus, b, is inserted at an acute angle into the smaller curvature, which rather resembles a deep cleft. The cardiac cul-desac, c, is very capacious, and is lined throughout internally with a thick cuticular layer continuous with the lining of the esophagus, and extends toward the pylorus as far as the middle of the

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cavity, where it terminates abruptly by a prominent indented edge: the interior of the pyloric half of the viscus, a, d, presents the usual villous mucous surface. The muscular coat of the stomach consists of several superimposed layers of fibres that cross each other in different directions, some of them being appa

1 Vomiting is rare and difficult; but has been observed in sea-sick horses slung on board transport-vessels.

rently derivations from the muscular bands of the œsophagus.' The alimentary canal is short in comparison with that of the Ruminants; but this want of length, together with the simplicity of the stomach, is compensated by the enormous capacity of the large intestine, which seems of itself to occupy the whole of the abdominal cavity, fig. 359.2

Commencing from the pylorus, the duodenum, fig. 358, f, is considerably dilated; but its diameter soon contracts, and the rest of the tract of the small intestines is of pretty equable dimensions throughout, or if it presents constrictions here and there, they disappear when the gut is distended. The ileum, fig. 360, d, terminates in a cæcum of enormous bulk, ib. a, b, c, e,

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folds, fig. 359, a, b, mount upward as far as the diaphragm, whence they descend to the left iliac region, where, becoming gradually contracted, the great gut terminates in the rectum. The ascending portion of the colon, a, b, is separated from the descending part, c, d, by a constriction; and the latter forms a third remarkable dilatation before it ends in the rectum. The whole colon is puckered up into huge sacculi by three longitudinal muscular bands, which toward the end of the colon are reduced to two; and these expand and coalesce at the beginning of the rectum, of which they form the strong outer muscular layer. The small intestines are about 56 feet in length: the cæcum is 24 feet in length and about 2 feet in circumference. The colon maintains the same circumference to near its termination, save that, about a yard from the cæcum, it becomes much dilated its length is 21 feet.

At certain seasons the stomach of the Horse is infested with the larvae of a gad-fly (Estrus equi). Daubenton figures the cavity in this state. CXXI'. pl. v, fig. 2. 2 CXXII. vol. iv. pls. Iv-v.

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