THE DIGESTIVE ORGANS. 



143 



ated in the submucous coat. From these plexuses fibres are dis- 

 tributed to the muscles and other structural elements. These fibres 

 are of the non-medullated variety. 



The nerves of the pancreas are also non-medullated, possess a 

 few ganglia within the organ, and are finally distributed among the 

 epithelial cells. 



The Tonsils, Lymph-follicles, and Peyer's Patches. These collec- 

 tions of lymphadenoid tissue in the alimentary tract have special 



FIG. 122. 





.-Section of human pancreas. (Bohm and Davidoff.) a, larger duct ; b, beginning of duct ; c, d, 

 acini with cells belonging to the corresponding duct-radicles in their centers ; e, acinus, 

 cut just beyond the lumen ; /, interalveolar cell-group (?) ; g, fibrous connective tissue, 

 forming the interstitial tissue of the organ. 



interest to the physician as being points particularly liable to infec- 

 tion. The solitary follicles of the stomach and of the small and 

 large intestine, and the collections of such follicles forming the 

 patches of Peyer, are the sites which are most vulnerable to 

 invasion by pathogenic bacteria in the digestive tract, though they 

 are probably protected to a considerable extent by the germicidal 

 powers of the acid gastric juice. This is not always capable of 

 guarding them from infection by the typhoid and tubercle bacilli, 

 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 

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



