310 DIGESTION. 



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 valvular conniventes. 

 Its general microscopic structure resembles that of the 

 small intestine. 



Glands of the Large Intestine. The glands with which 

 the large intestine is provided are of two kinds, the tubular 

 and lenticular. 



The tubular glands, or glands of Lieberkiihn, resemble 

 those of the small intestine, but are somewhat larger 

 and more numerous. They are also more uniformly 

 distributed. 



The lenticular glands are most numerous in the caecum 

 and vermiform appendix. They resemble in shape and 

 structure, almost exactly, the solitary glands of the small 

 intestine, and, like them, have no opening. Just over 

 them, however, there is commonly a small depression in 

 the mucous membrane, which has led to the erroneous 

 belief that some of them open on the surface. 



The functions discharged by the glands found in the 



