530 



THE TISSUES. 

 Fig. 359. 



Fig. 360. 



Vertical section through a patch of Peyer s glands in the dog. a. Villi. l>. Glands of Lieberkiihn. 

 with the apices of Peyer's glands, c. Submucous tissue, with the glands of Peyer imbedded in it. 

 d. Muscular and peritoneal coats, e. Apex of one of Peyer's glands projecting among the tubes of 

 Lieberkiihn. s. Its contents. The glands are seen laid open by the section. (Magnified about 20 

 diameters.) 



no villi. When, however, the follicles are isolated (glandulae soli- 

 tarise), they usually present a convex surface, and support villi. 

 (Fig. 360.) Each follicle has a completely closed, thick, and strong 

 coat of indistinctly fibrillated collagenous tis- 

 sue, with interposed nuclei; within which are 

 the soft grayish contents, consisting of a little 

 fluid, and innumerable nuclei and round cells, 

 Wffu to T^fii) f an i QC h i n diameter. Very 

 fine bloodvessels ramify, like those of the closed 

 follicles of the tonsils, on the exterior of these 

 follicles (Fig. 350), and penetrate to their inte- 

 rior. (Frei and JErnst.} Lymphatics also form 



A solitary gland from the J J J. 



networks around them; but do not enter them, 



as Brucke asserted. (KoWker) 



The patches of Peyer are from 20 to 30 in 

 number, when confined, as usual, to the ileum and lower part of the 

 jejunum; from 50 to 60 when extending nearly to, or even into, the 

 duodenum. They are rounded or elliptical in form, always situated 

 on the portion of intestine opposite the mesentery, and are J of an 

 inch to even 1 inch long, and J to even } of an inch broad. They 

 are mere aggregations of the closed follicles just described, each 



intestine of the hu- 



