IMMUNITY AND DIGESTION 253 



into simpler soluble proteins of the second order. Indeed we 

 have this remarkable fact that if, instead of allowing them to 

 be absorbed and acted upon by the intestinal mucosa, we intro- 

 duce these peptones and proteoses directly into the circulation, 

 they are found to be highly toxic. There is evidently, therefore, 

 a pronounced difference between enteral or intestinal, and 'paren- 

 teral digestion, the breaking down, that is, of foreign proteins 

 introduced into the organisms outside of, and without the 

 intermediation of, the digestive tube. 



We owe to Victor Vaughan, of Ann Arbor, and his long con- 

 tinued studies from 1901 onwards, the demonstration of the fact 

 that outside the body, by the simple procedure of digestion with 

 several times its bulk of absolute alcohol in the presence of 2 per 

 cent of sodium hydroxide, any protein — even so apparently 

 harmless a body as egg albumen — is split up into a poisonous 

 and a non-poisonous moiety, the former soluble in alcohol, the 

 latter insoluble, and this poisonous moiety, when introduced 

 into the system other than through the intestine, is rapidly fatal 

 in doses so minute as from 8 to 100 mg. per guinea-pig. Evidently 

 in the process of passage through the intestinal mucosa, either 

 this poisonous moiety of the protein molecule is detoxicated, 

 or protein disintegration there is so carried on that it is never 

 given off. 



The high significance of these observations lies in this, that 

 the bacterial bodies are largely compounded of proteins, that 

 bacterial bodies similarly treated give these same poisonous 

 and non-poisonous moieties : that the process of destruction 

 of bacteria that have gained entrance into the tissues is one of 

 parenteral digestion, and that the phenomena associated with 

 parenteral digestion must therefore be closely studied in order 

 to understand the nature of infection and the phenomena of 

 immunity. It is this study that has ushered in the latest phase 

 of our subject ; and in this subject two names stand out par- 

 ticularly, those of Victor Vaughan and Abderhalden. Perhaps 

 it would be equally correct to state that this latest phase corre- 

 sponds with the study of anaphylactic phenomena, and of their 

 relationship to immunity, for, as I shall proceed to show, the two 

 are most intimately connected. 



