388 INFECTION AND IMMUNITY. 



for intoxication larger amounts are necessary than 

 for sensitization. 



Wells has also shown that toxicity and sensi- 

 tizing properties decrease equally by tryptic diges- 

 tion, and that both disappear with the disappear- 

 ance of heat coagulable proteins. According to 

 Wells, the importance of the action of heat is due 

 to the coagulation of protein, thus rendering it 

 capable of being taken up and digested by the 

 leucocytes. Casein and other proteins which do 

 not coagulate on boiling suffer no change through 

 heat until a temperature which destroys the pro- 

 tein molecule is reached. 



That toxic and sensitizing substances may be 

 closely related to the aromatic groups of the pro- 

 tein molecule is suggested by the fact that gelatin 

 which is devoid of tyrosin and contains little of 

 other aromatic groups does not produce the phe- 

 nomena of anaphylaxis (Wells). 



By the injection of serum of sensitized animals 

 it is possible to produce a passive sensitization, 

 analogous to passive immunity, and in this way 

 to demonstrate the presence of an anaphylactic 

 antibody. This antibody has received the name of 

 "anaphylactin" (Eosenau and Anderson), or "al- 

 lergin" (Anderson and Frost). It is possible to 

 produce passive anaphylaxis in various animals, 

 but, as in active anaphylaxis, the guinea-pig is 

 best adapted to the purpose. Transmission of 

 anaphylaxis from one species to another is also 

 possible. From rabbit to guinea-pig anaphylaxis 

 is readily transmitted. 



The necessary interval of time elapsing between 

 the injection of the serum containing anaphylactic 



