424 



ANATOMY OF VERTEBRATES. 



320 



faeces 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 

 length of the body, the large intestines once that length. In 



the Mole-rat {Bathyergus) the caecum 

 makes a close spiral turn, and its inner 

 membrane is augmented by many trans- 

 verse folds. The caecum is of greater 

 length in the Sciurida : in the common 

 Squirrel it is curved, fig. 320, c, and 

 divided from the colon, e, by a constric- 

 tion close to the termination of the ileum. 

 The colon is wider at its commencement 

 than in the Rats, and the whole intes- 

 tinal canal is longer. In Sciurus griseus 

 the small intestines are seven times, the 

 large intestines twice, the length of the 

 body; the caecum is half that length. 

 In the Hamster the colon describes two 

 direct and two reflected spiral coils at 

 its commencement, decreasing in calibre, 

 and then proceeds, of nearly the same 

 diameter as the ileum, to terminate in 

 the rectum. 1 In the Marmots (Arctomys) 

 the duodenum passes loosely down the 

 right side until its attachment, by a 

 mesentery from its concavity, to the first 

 bend of the colon, behind which it winds 

 to the left; and after an attachment to the 

 descending colon by serous layers from 

 its convexity, becomes jejunum. The 

 long and large caecum has a mesentery ; 

 its inner surface is multiplied by circular folds, indicated outwardly 

 by constrictions which led Hunter to compare it ' to a quilted pet- 

 ticoat.' a The indication of the low grade or affinities yielded by 

 the termination of the intestines, is thus noted in the present 

 Lissencephalan : — 'The rectum cannot be said to terminate at the 

 verge of the anus ; but about three-quarters of an inch higher up, 

 that lower part seems common to the anus and to a glandular appa- 

 ratus whose ducts open into it. It is something like the common 

 vagina to the bladder and uterus in fowls.' 3 In Capromys the ileum 



1 cxxn". xxni. p. 134, pi. xv. 2 ccxxxvi. vol. ii. p. 242. 



3 lb. p. 243. 



Caecum of the Squirrel, cxxir 



