4 ANAPHYLAXIS AND ANTI-ANAPHYLAXIS 



on a single occasion. What again is perplexing to 

 the last degree is that substances such as egg-albumen, 

 milk, and serum, which may be employed in almost 

 unlimited quantities on ordinary occasions, become 

 deadly in doses that are almost infinitesimal during 

 periods of anaphylaxis. 



Such is the riddle which numerous scientists have 

 sought to explain. What is the source of this toxi- 

 city which nothing justifies and which nevertheless 

 makes its appearance with such suddenness and 

 violence at the time of reinjection of the same sub- 

 stance ? 



Clearly this toxicity can only originate in some 

 change that takes place in the body of the animal 

 itself under the influence of the first injection. 



We shall return to this point in the course of this 

 monograph, more especially in the chapter devoted 

 to Theories relating to Anaphylaxis. 



