THE STOMACH AND INTESTINE. 



28l 



4. THE LARGE INTESTINE, RECTUM, AND ANUS. 



The small intestine ends at the ileocecal valve. At some dis- 

 tance from the margin of the valve the villi of the ileum become 

 broad and low. In the immediate vicinity of the valve their basilar 

 portions become confluent, forming a honeycomb structure which 

 supports a few villi. At the base of the honeycomb open the glands 

 of Lieberkuhn. On the cecal side of the valve the villi become 

 fewer in number and finally disappear, while the folds which give 

 the honeycomb appearance persist for a considerable distance. In 



Fig. 221. Transverse section of human vermiform appendix; X 20. Observe the 

 numerous lymph nodules. The clear spaces in the submucosa are adipose tissue. 



the adult cecum the villi are absent. The mucosa and glands pre- 

 sent a structure similar to that of the remainder of the large intes- 

 tine. In the mucosa of the vermiform appendix is found a relatively 

 large number of solitary lymph-follicles, occasionally forming a 

 continuous layer. The marked development of the lymph-follicles 

 encroaches upon the glands of Lieberkuhn, so that many are 

 obliterated ; they are penetrated by the adenoid tissue, the epithe- 

 lial cells of the glands mingling with the lymph-cells. What finally 

 becomes of the secretory cells has not been definitely ascertained 

 (Riidinger, 91). 



