DIGESTION. 



20 7 



called appendices epiploicce. The fibres of the muscular coat, like those- 

 of the small intestine, are arranged in two layers the outer longitudinal, 

 the inner circular. In thecajcum and colon, the longitudinal fibres, be- 

 sides being, as in the small intestine, thinly disposed in all parts of the 

 wall of the bowel, are collected, for the most part, into three strong 

 bands, which, being shorter, from end to end, than the other coats of the 

 intestine, hold the canal in folds, bounding intermediate sacculi. On 

 the division of these bands, the intestine can be drawn out to its full 

 length, and it then assumes, of course, an uniformly cylindrical form. 

 In the rectum, the fasciculi of these longitudinal bands spread out and 



FIG. 200. A. Villus of sheep. B. Villi of man. (Slightly altered from Teichmann.) 



mingle with the other longitudinal fibres, forming \vith them a thicker 

 layer of fibres than exists on any other part of the intestinal canal. The 

 circular muscular fibres are spread over the whole surface of the bowel, 

 but are somewhat more marked in the intervals between the sacculi. 

 Towards the lower end of the rectum they become more numerous, and 

 at the anus they form a strong band called the internal sphincter muscle. 

 The mucous membrane of the large, like that of the small intestine, 

 is lined throughout by columnar epithelium, but, unlike it, is quite 

 smooth and destitute of villi, and is not projected in the form of valvulcB 

 conniventes. Its general microscopic structure resembles that of the 

 small intestine : and it is bounded below by the muscularis mucosce. 



