DISSOCIATION IN THE TOXIN-ANTITOXIN COMBINATION. 671 



TABLE VI. 



for some time. With mixtures that have stood 24 hours before dilut- 

 ing, there is practically no increase in toxicity as a result of dilution, 

 and this is all the more noticeable because the mixture which stood 

 24 hours contained only three-quarters of the quantity of toxin con- 

 tained in that which stood only three hours. It is necessary, there- 

 fore, to distinguish two phases in the reaction between toxin and 

 antitoxin, a primary phase in which neutralization has taken place, 

 but in which dilution suffices to again liberate some of the toxin, and 

 a secondary phase in which this is no longer possible or is possible 

 only to a very slight degree. The assumption of these two phases 

 accords completely with Ehrlich's views concerning the relations 

 existing between toxin and antitoxin. We assume that in the toxin- 

 antitoxin reaction there exists a stage in which the reaction is to a 

 certain extent reversible, and that this is succeeded by a tightening 

 of the bonds, a stage of firm union, in which the reversibility is lost. 

 The most striking example of this secondary tightening is that known 

 as the Danysz-Dungern 1 phenomenon, which consists in the demon- 

 stration of increased toxicity of toxin-antitoxin mixtures by the 

 fractional additional of the toxin. 



In the phenomenon which we are studying, the first stage of the 

 reaction, namely, that of reversibility, is brought out by diluting the 

 mixtures. It has, of course, long been known that the union of 

 toxin and antitoxin proceeds more rapidly in concentrated than in 

 dilute solutions, and this has from the outset been emphasized by 

 Ehrlich. WTiat was new about these observations was the fact that 

 neutralized, concentrated toxin-antitoxin mixtures could be disso- 



1 v. Dungern, Deutsch. med. Wochenschr., 1904; Sachs, Berl. klin. Wochen- 

 schr., 1904; and Centralbl. Bacteriol. I Abt., Orig. Vol. XXXVII, 1904. 



