192 MANUAL OF PHYSIOLOGY. 



of the leucin and tyrosin, although this is in a great measure held 

 in check by the antiseptic nature of the bile. 



It is in the large intestine that putrefactive fermentations have 

 the greatest effect, the acid reaction being caused by the various 

 acids produced. 



With regard to the interesting question, Why do not the 

 digestive fluids dissolve the tissues of the organs in which they 

 are contained, we cannot speak positively. We cannot now say 

 that the " vital principle " has a protective influence, for we 

 know the fact that a tissue being alive is not sufficient to ward 

 off the digestive action of the alimentary juices, since the limb of 

 a living frog is digested when introduced through a fistula into 

 the stomach of a dog ; and when the intestinal juice trickles from 

 a fistula the neighboring skin, the snout, and the tongue of the 

 animal soon become eaten away owing to its licking the fluid, 

 which rapidly digests these parts so as to destroy the skin and 

 even expose the blood vessels. 



We can, however, modify John Hunter's statement that the 

 resisting power was associated with the life of the structures, by 

 saying that it is not the property of an abstract " vital principle," 

 but a special resisting power dependent upon the specific charac- 

 ter of the vital processes of certain textures. 



