In the Rodentia the stomach is separated by an external constriction into tvi-o portions: —a cardiac, clothed with a thick epidermis, and a pyloric, occupied by a mucous mem brane which has the ordinary tubular struc ture. The size of the former pouch varies in different genera ; the latter sometimes pre sents an imperfect subdivision. The whole organ occasionally approaches a conical or spherical shape. In the Beaver and Muscar din, the stomach is complicated by the addi tion of glandular crypts and cmca, the im port of which is unknown. The intestine of the Rodent is very long and convoluted, and the small and large intestine are of nearly equal diameter; but the latter is deeply sac culated. The cmcum is usually very large, and is sometimes subdivided by spiral or cir cular folds. But in the omnivorous Rat it is small ; and in the Dormouse it is altogether absent.
Marsupialia. —In a large proportion of this order, the stomach has a considerable resem blance to that of the human subject. Such an organ is found in both carnivorous and herbivorous Marsupialia : and indeed, it is difficult to point out any differences in its size or shape which are distinctly referrible to the habits of its possessors. In some, how ever, a stomach of very similar outside shape exhibits a lesser curvature, vihich is oc cupied by a gastric gland like that of the Beaver, composed of numerous irregular crypts. In the Kangaroo (111neropus) both the shape and the structure of the organ differ widely from the preceding. The stomach is of a length which equals that of the whole body ; the cardiac pouch is subdivided into two cwca ; and the middle part of the organ is sacculated by three bands of longitudi nal 'muscular fibres, so as closely to resem ble the ordinary arrangement of the colon,— except that the interspace between the upper two, or that third of the surface which occu pies the lesser curvature, is not sacculated. The gastric gland is broken up into numerous follicles, which are placed in three rows parallel to the longitudinal muscular bands. The mucous menibrane of the cesophagus is continued right and left of the cardiac orifice for a considerable distance ; some what as in the stomach of the Pig. The re mainder of the mucous membrane is of the ordinary soft character.
The intestine of the Marsupial is also sub ject to great differences. The carnivorous members of the class are devoid of a cxcum.
The insectivorous Marsupials have a longer intestinal canal, vt hich is separated into large and small intestine, and exhibits a cmcum of moderate size. Those that live upon fruits have bowels which are still longer, and a large cwcum of twice the length of the whole body. Finally, the true vegetivorous genera have a ccuin which is thrice as long as the body. In those which are possessed of a saccu lated stomach, the cmcum is, however, much shorter. One genus, the Wombat, has a vermiform appendix. The length of the whole
intestine varies from two to ten times the length of the animal.
In the Monotremata the alimentary canal is chiefly remarkable from its terminating in a cloaca common to it and the urinary and generative organs. A small ccum separates the long and narrow bowel into two parts. The diameter of the small intestine gradually diminishes to the cmcum, while that of the large intestine gradually increases to the rec tum.
The Cetacea offer two chief varieties of stomach, which are connected with differences in their food, though scarcely explained by them. Those which live on vegetable food exhibit a simpler form of organ. Thus, in the Dugong, the stomach is long and transverse; and is divided by a deep constriction into a globular cardiac, and a conical pyloric, portion. Two large caeca open into it near this con striction ; and a special glandular apparatus occupies the upper part of the cardiac pouch. In the carnivorous Cetaceans, the stomach is subdivided into three, five, seven, or more cavi ties. In some genera, however, there are only four. Of these the first has an epidermoid lining, while the three last have a soft mucous membrane. The biliary duct often opens into a dilated cavity, the import of which is unknown. The intestine is longer in the herbivorous di vision. Here there is also a coecum ; which is sometimes large and glandular, but some times small, short, and even bifid. In the zoophagous Cetaceans there is rarely either excum or valve:—so that the intestine, which decreases slightly in size from the pylorus to the anus, offers no separation into large and small. But in the genus Balcena there is a small cmcurn, like that of the Cat.
The Quadruniana possess a stomach the form of which approaches that of the human organ. In some cases, however, it is more elongated ; while in others it assutnes a glo bular shape, with a cardia and pylorus in close proximity. The latter deviation is generally found in conjunction with carnivorous or insectivorous habits. It is usually separated into two portions, a cardiac and a pyloric ; and sometimes the latter, which is more glohuhr than usual, is distinguished by an internal fold from a short tubular part, which termi nates in the pyloric valve and the duodenum. Rudimentary pyloric cmca have been retnarked by Cuvier in one instance. The Sem. nopithecus presents a form of stomach which recalls that of the Kangaroo. For the cardiac cavity, smooth and ahnost bifid at its com mencement,issoon sacculated by a superior and inferior band of longitudinal fibres which conic from the cesophagus ; and from thence the sto mach continues to the right side, as a saccu lated tube, which is bent upon itself, and closely resembles a large intestine. But before reach ing the pylorus, these sacculi diminish and dis appear.