182 IMMUNE SERA 



ceivable that the condition is really an immunity 

 reaction. Looking at the entire question broadly 

 we may regard the mechanism which lies at the 

 bottom of the phenomenon of anaphylaxis as a 

 useful contrivance which enables the organism to 

 rid itself of alien proteid, both organized and un- 

 organized, which has been introduced parenterally. 



Immunity Reaction on the Part of Bacteria. It 

 may be well at this point to call attention to a view 

 advanced by Welch some years ago. According to 

 this it is reasonable to suppose that just as the 

 animal body produces antibodies against an invad- 

 ing organism, so does the latter, owing to the action 

 of the body fluids, produce antibodies directed 

 against the tissues of the invaded body. In this 

 way the infecting organism w r ould be adapting itself 

 to unfavorable surroundings, and this we know it 

 often does. It is certain that the animal body often 

 successfully overcomes an infectious disease without 

 entirely overcoming the infecting bacteria. This is 

 well shown by what we call chronic germ carriers. 

 Deutsch regards the increase in virulence brought 

 about by successive passage of a bacterium through 

 a susceptible animal as representing an immunity 

 developed by the bacterium against the anti- 

 bacterial agencies of the body. 



Atrepsy. Ehrlich has investigated this phe- 

 nomenon in the case of trypanosomes. He found 

 that a monkey which had been infected with a 



