454 THE ALIMENTARY CANAL. [CH. xxvii. 



resembles that of the small intestine : and it is bounded below 

 by the muscularis mucosce. 



The arrangement of ganglia and nerve-fibres in the large 

 resembles that in the small intestine. 



Glands. The glands with which the large intestine is provided 

 are simple tubular glands, or glands of Lieberkiihn ; they re- 

 semble those of the small intestine, but are somewhat larger and 

 more numerous, and contain a very great number of goblet cells ; 

 nodules of adenoid or lymphoid tissue are most numercms in the 

 csecum and vermiform appendix. They resemble in shape and 

 structure the solitary glands of the small intestine. Peyer's 

 patches are not found in the large intestine. 



Heo-ccecal Valve. The ileo-csecal valve is situated at the place 

 of junction of the small with the large intestine, and guards 

 against any reflux of the contents of the latter into the ileum. 

 It is composed of two semilunar folds of mucous membrane. 

 Each fold is formed by a doubling inwards of the mucous mem- 

 brane, and is strengthened on the outside by some of the 

 circular muscular fibres of the intestine, which are contained 

 between the outer surfaces of the two layers of which each fold 

 is composed. While the circular muscular fibres, however, at the 

 junction of the ileum with the csecum are contained between 

 the outer opposed surfaces of the folds of mucous membrane 

 which form the valve, the longitudinal muscular fibres and 

 the peritoneum of the small and large intestine respectively 

 are continuous with each other, without dipping in to follow the 

 circular fibres and the mucous membrane. In this manner, 

 therefore, the folding inwards of these two last-named structures 

 is preserved, while on the other hand, by dividing the longitu- 

 dinal muscular fibres and the peritoneum, the valve can be 

 made to disappear, just as the constrictions between the sacculi 

 of the large intestine can be made to disappear by performing 

 a similar operation. The mucous membrane of the ileum is 

 continuous with that of the csecum. That surface of each 

 fold of the ileo-csecal valve, which looks towards the small in- 

 testine is covered with villi, while that which looks to the csecum 

 has none. When the csecum is distended, the margins of the 

 folds are stretched, and thus are brought into firm apposition one 

 with the other. 



