THE DIGESTIVE ORGANS. 



149 



small intestine there are collections of these solitary follicles, which 

 have received the name " Peyer's patches." 



6. The small intestine below the duodenum resembles the latter 



Fig. 128. 



Section of solitary follicle from the ileum. (Cadiat. I a, space left by the disintegration of 

 the central, delicate lymphadenoid tissue of the follicle during the preparation of the sec- 

 tion; b, columnar epithelium of intestinal surface; c, r, villi, partially denuded of epithe- 

 lium ; d, crypt; e, /, muscularis mucosae; above /, the point where the vessels enter the 

 follicle. The Peyer's patches are collections of such solitary follicles, placed side by side 

 and destitute of villi at their upper surfaces. 



in structure, with a few modifications, which become progressively 

 more marked as the distance from the stomach increases. 



The glands of Brunner are most abundant near the upper part 

 of the duodenum, more sparsely distributed further down, and 

 usually disappear entirely before the beginning of the jejunum. 



The valvulae conniventes, which are most highly developed a 

 little below the entrance of the gall and pancreatic ducts, also 

 become lower and less frequent along the course of the intestine, 

 and finally disappear about the middle of the ileum. 



The crypts of Lieberkiihn are deepest in the upper part of the 

 intestinal tract, but persist in shallower form throughout its whole 

 extent, as well as along the whole length of the colon. 



The Peyer's patches are most abundant in the lower part of the 

 ileum, where they lie in the intestinal wall opposite the line of 

 mesenteric attachment, and form oval areas with their long axes 

 parallel to the axis of the intestine. 



7. The Colon. — The mucous membrane of the colon is destitute 



