30 LECTURES ON IMMUNITY 



toxin is destroyed by antitoxin without a diminution of the 

 quantity of the latter substance. Chemically speaking, the 

 antitoxin acted as a catalysator. This idea was incom- 

 patible with the measurements of Ehrlich on diphtheria- 

 poison, according to which the double quantity of antitoxin 

 neutralises the double quantity of poison. Ehrlich there- 

 fore held the opinion that a real chemical combination 

 takes place. On the other hand, Buchner 1 and Roux 2 

 supposed that this action of antitoxin on toxin takes place 

 only in the susceptible animal. According to their opinion 

 the antitoxin really reacts upon the animal, stimulating it 

 in the struggle against the poison. This idea was supported 

 by such experiments as those of Calmette, according to 

 which toxin and antitoxin coexist in their mixtures. Against 

 this type of explanation, Ehrlich carried out his experi- 

 ments on the neutralisation of toxins "in vitro," outside of 

 the living animal, and Martin and Cherry showed that experi- 

 ments similar to Calmette's might be due to an insufficient 

 time of reaction. The experiments "in vitro" have been mul- 

 tiplied in great number and the influence of the time of 

 reaction has been observed in most cases investigated, so 

 that the idea of the chemical combination between toxins 

 and antitoxins has been generally accepted. But their in- 

 complete knowledge of limited chemical reactions caused 

 Ehrlich and other investigators of these phenomena to 

 suppose that the processes observed are always unlimited; 

 and accordingly they were unable to explain all the phenom- 

 ena indicating the existence of chemical equilibria be- 

 tween the substances examined. To explain some of these 



1 Buchner: Deutsche med. VVochenschrift, 480(1903). 



2 Roux and Vaillard: Ann, de rinst. Pasteur, 8. 724 (1894). 



