THE ILEO-CLECAL YALVE. 317 



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 large intestine are not known with any certainty, 

 but there is no reason to doubt that they resemble very 

 nearly those discharged by the glands of like structure in 

 the small intestine. 



The difficulty of determining the function of any single 

 set of the intestinal glands seems indeed almost insuper- 

 able, so many fluids being discharged together into the 

 intestine ; for all acting, probably, at once, produce a com- 

 bined effect upon the food, so that it is almost impossible 

 to discern the share of any one of them in digestion. 



lleo-cacal valve. The ileo-csecal valve is situate 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 membrane, 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. The inner surface 

 of the folds is smooth ; the mucous membrane of the ileum 

 being continuous with that of the caecum. That surface 



