3*6 DIGESTION. 



continuous with the ceecum, which forms the principal 

 part of the large intestine, and is divided into an ascend- 

 ing, transverse and descending portion ; and the rectum 

 which, after dilating at its lower part, again contracts, 

 and immediately afterwards opens externally through the 

 anus. Attached to the caecum is the small appendix 

 vermiformis. 



Like the small intestine, the large is constructed of three 

 principal coats, viz., the serous, muscular, and mucous. 

 The serous coat need not be here particularly described. 

 Connected with it are the small processes of peritoneum 

 containing fat, called appendices epiploicce. The fibres of 

 the muscular coat, like those of the small intestine, are 

 arranged in two layers the outer longitudinally, the 

 inner circularly. In the csecum and colon, the longi- 

 tudinal fibres, besides 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 inter- 

 mediate sacculi. On the division of these bands, the intes- 

 tine 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 mingle with the other longitudinal fibres, forming 

 with 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 epithe- 

 lium, but, unlike it, is quite smooth and destitute of villi, 

 and is not projected in the form of valvulse conniventes. 



