LYMPHOID ORGANS. 



i'3 



tication has not yet been furnished, but the facts are undoubt- 

 edly the same. 



Let us now pass from the simple to the complicated. 



Let us take the amygdale or tonsils (Fig. 108). These, 

 subjected to many changes in the mammalia, show in the 



Fig. ioS. — Tonsil of the adult (after Schmidt); a, larger excretory duct ; b, more simple one ; 

 c, lymphoid parietal layer, with follicles ; d, lobule, reminding one of a lingual follicle ; e, superficial ; 

 f, deeper mucous follicle. 



human body a complicated system of fossse in the surface of the 

 mucous membrane. The passages of these depressions open 

 in part conjointly (a), in part separately (b). At the peri- 

 phery of the follicular aggregation, there are often still smaller 

 and shallower fossae (c). The cavities are lined with the 

 pavement epithelium of the mouth. A thick, lymphoid 

 parietal layer (c), surrounded externally by a connective- 

 tissue capsule, invests the entire system of fossae. In this 

 lymphoid tissue occur rounded bodies of a large-meshed 

 structure and a brighter appearance. These are the follicles. 

 In the narrow-meshed connecting tissue, one recognizes 

 reticular passages which circumvallate these bodies. They 

 form the paths for the lymph, as the injection shows. 



Simplified formations are presented by the lingual follicles 

 on the posterior portion of the dorsum of the tongue. Their 

 structure reminds one of the place d of our Fig. 108. 



The so-called trachoma glands have a similar structure, but 

 spread out flatter, and are without fossae (Fig. ioi). They 

 likewise present brighter follicles (b), as well as a narrower- 

 meshed and therefore, again, more opaque connecting layer. 

 In the latter runs a more developed lymphatic canal-work (c), 



