SENSITISING INJECTION 25 



Von Pirquet and Schick had already expressed the 

 opinion that horse serum when injected would give 

 rise in the body of the animal to a reaction product 

 which is a kind of antibody (" anti-Korperartiges 

 Reaktionsprodukt ")} These authors thus explained 

 the incubation period, which is observed in indivi- 

 duals injected with the serum, and which lasts eight 

 to twelve days, and never less than six days. 



In the opinion of Rosenau and Anderson also, the 

 anaphylactic state was due not to the substance in- 

 jected, but to the reaction which this substance set up 

 in the animal, a reaction which is made possible by 

 the formation of antibody. 



From the date of our first experiments dealing 

 with anaphylaxis we have been very positive about 

 this: " Under the influence of a very weak dose of 

 normal serum injected subcutaneously," we wrote in 

 collaboration with Steinhardt, " the guinea-pig elabo- 

 rates a new substance — namely, a sensibilisinP' 



In the course of his studies on Arthus's pheno- 

 menon in the rabbit Nicolle® was successful in obtain- 

 ing a clear view of the presence of sensibilisin ; in 

 fact, he was enabled to produce Arthus's phenomenon 

 in fresh rabbits by injecting them with serum derived 

 from prepared rabbits. 



Working on the same lines, Charles Richet* carried 

 out the following pretty experiment: A dog was 

 twice injected with crepitin, one month being allowed 

 to elapse between the injections. Six weeks after the 

 second injection the dog was venesected : it need hardly 

 be said that its serum was innocuous. To this serum 

 Richet added some crepitin in an innocuous dose : 

 the mixture was forthwith injected into a fresh dog. 

 The animal was immediately seized with acute ana- 



* Loc. cit. 2 Annates de I'Institut Pasteur, 1907, xxi., p. 384- 

 ^ Ibid., p. 136. 



* Comptes rend. Soc. de Biol., 1909, Ixvi., p. 1055. 



