IV 



ANAPHYLAXIS OR HYPERSUSCEPTIBILITY 

 Ix connection with the administration of antisera 

 for therapeutic purposes, the possibihty of the occur- 

 rence of the phenomenon known as anaphylactic shock 

 must be borne in mind. 



The phenomenon of protein sensitization was rec- 

 ognized by Vaughan, von Behring and others for 

 many years before the name anaphylaaJis, under which 

 it is now generally known, was given by Richet in 

 1911. The term indicates absence of protection, as 

 opposed to prophylaxis. Anaphylaxis consists in a 

 series of apparently deleterious effects produced by a 

 second injection of specific protein material into an 

 animal that has been previously *' sensitized " by a 

 first injection of the same material. For instance, if 

 an animal receive one injection of a foreign protein 

 material, say of antitoxic serum, no deleterious effects 

 are usually observed, but if this injection be repeated 

 after several days, even in a very small dose, the 

 second injection may be followed immediately by a 

 marked reaction, such as convulsions and respiratory 

 difficulty, in some cases with a fatal result. The ana- 

 phylactic phenomena usually follow when the second 

 injection is given at least twelve days after the first. 



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