920 



THE ORGANS OF DIGESTION. 



a rule, possess villi on their free surface. Each patch is surrounded by a circle 

 of the crypts of Lieberkiihn. They are best marked in the young subject, becoming 

 indistinct in middle age, and sometimes altogether disappearing in advanced life. 



FIG. 504. Vertical section of one of Peyer's patches from man, injected through its lymphatic canals, a. 

 Villi with their chyle-passages. 6. Follicles of Lieberkuhn. c. Muscularis mucosae. d. Cupola or apex of soli- 

 tary glands, e. Mesial zone of glands. /. Base of glands, q. Points of exit of the chyle-passages from the 

 villi, and entrance into the true mucous membrane. A. Retiform arrangement of the lymphatics in the mesial 

 zone. i. Course of the latter at the base of the glands, k. Confluence of the lymphatics opening into the 

 vessels of the submucous tissue. I. Follicular tissue of the latter. 



They are largely supplied with blood-vessels, which form an abundant plexus 

 around each follicle and give off fine branches which permeate the lymphoid tissue 

 in the interior of the follicle. The lacteal plexuses which are found throughout 



HiMipolar ganglion- cells. 



FIG. 505. Meissner's plexus. (Klein and Noble Smith.) 



the small intestine are especially abundant around these patches ; here they form 

 rich plexuses with sinuses around the glands (Fig. 504). 



