THE DIGESTIVE ORGANS. 153 



and in the diseases of* the intestinal canal occasioned by those bac- 

 teria the follicles and Peyer's patches are the seat of the earliest 

 and most extensive ulcerations. The tonsils, which have the same 

 general structure, are still more prone to infection of various kinds, 

 for they are more directly exposed to the action of bacteria that may 

 train access to the month. 



The reason for this vulnerability appears to lie in the close prox- 

 imity of the lymphatics to the surface and their meagre protection 

 by a thin layer of epithelium liable to abrasion or destruction. The 

 solitary follicles of the intestine, for example, are covered with a 

 single layer of columnar epithelium (Fig. 128). 



The lymphadenoid tissue of the tonsil, it is true, is protected by 

 a layer of stratified epithelium ; but the surface of the tonsil is invag- 

 inated to form the crypts of that organ, and within those crypts it 



Section through the fundus of a erypt. (Benda ami Guenther's Atlas.) a, stratified epithe- 

 lium, desquamating at its surface ; 6, deep portion of the lymphadenoid tissue, in which 

 proliferation of lymphoid cells takes place as well as in the follicles represented in Fig. 131. 



is possible for bacteria to multiply and produce such an accumula- 

 tion of poisonous products as to destroy the integrity of the epithe- 

 lium and so permit an invasion of the lymphadenoid tissue beneath. 

 We therefore find the tonsils specially prone to such inflammatory 

 processes as tonsillitis and diphtheritic inflammation (Figs. 131 and 

 132). 



