. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. RODENTIA. 389 The colon (e) is for a short distance almost of the same diameter as the caecum, but it soon diminishes in size, and throughout the rest of its extent is scarcely wider than the small intestine. Internally, it presents no septa or valvulae conniventes. The intestinal papillae form small lamella?, the borders of which are fringed with delicate filaments ; these papilla? extend throughout the whole length of the small intestine, but towards its termination becomes smaller and less per- ceptible. In the rats,
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. RODENTIA. 389 The colon (e) is for a short distance almost of the same diameter as the caecum, but it soon diminishes in size, and throughout the rest of its extent is scarcely wider than the small intestine. Internally, it presents no septa or valvulae conniventes. The intestinal papillae form small lamella?, the borders of which are fringed with delicate filaments ; these papilla? extend throughout the whole length of the small intestine, but towards its termination becomes smaller and less per- ceptible. In the rats, the alimentary canal would be nearly of the same calibre throughout, were it not for the interposition of the caecum between the ileum and the colon. The caecum in this family of Rodents rather re- sembles a second stomach (fig. 273. k, /) than a bowel ; it is capacious, short, and slightly curved upon itself, but without any constric- tions, tapering gradually towards its blind ex- tremity. The walls of the intestinal canal are throughout thin, delicate, and transparent; Fig. Cacum of the Water Vole (Aricola amplii/m/s). I, m, end of the small intestine ; n, o,p, q, cagcum ; r, dilated commencement of the colon; s, point at which the colon becomes contracted. but slight traces of a spiral valve are visible at the commencement of the colon. In the water-rat (Arvicola amphibius) the small intestines are of equable diameter throughout their whole extent, but their calibre is small, as indeed is that of the large intestine. The caecum is, however, of enor- mous proportions (fig. 274. n, o, p, q), and is divided at intervals into pouches by deep constrictions. The commencement of the colon (r) is extremely voluminous, but it soon diminishes in its diameter, and is twisted in a remarkable manner, so as to form several close spiral turns ; the walls of the small in- testine (/, m) are very thin and transparent; at the commencement of the colon its lining membrane is thrown int
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