LYMPHOID ORGANS. 



115 



In the follicle (Fig. 109), we distinguish three parts, the 

 apex (d), covered only by epithelium, and projecting between 

 adjacent villi (a) into the lumen of the intestine, then a middle 

 zone (at the elevation of c), and, finally, a basis portion (/). 

 The middle zone and basis portion are buried in the sub-mu- 

 cous cellular tissue. Here — and we are reminded of the tonsils 

 and trachoma follicles — the middle and lower portions are 

 united by a more narrow-meshed lymphoid tissue. The sur- 

 faces of both these parts are again surrounded by a lymphatic 

 canal-work in a reticular form. Not so in the follicles in the 

 small intestine of the ox, and in the processus vermiformis of 

 the rabbit. In these the basis portion is surrounded, similar 

 to the follicles of a lymphatic gland, by a connected cup-like 



JU 



Fig. iio. — Transverse section, through the equatorial plane of three Peyerian follicles of the 

 rabbit ; a, the capillary net-work ; b, the larger annular-shaped vessels. 



lymphatic investment space, while in the middle zone, it is 

 true, the reticular passages are still retained. 



The lymphatic injection shows interesting conditions, re- 

 minding us of those of the lymphatic glands, and the discover- 





