DISSOCIATION IN THE TOXIN-ANTITOXIN COMBINATION. 675 



prepared fresh antilytic sera by immunizing rabbits, and found that 

 these at once gave the paradoxical results under discussion. Con- 

 cerning the cause of this peculiar behavior of fresh and old anti- 

 toxin we can only offer conjectures. One could assume that on 

 standing the antitoxin becomes changed into a form possessing greater 

 affinity. It must be admitted that the experiences had with other 

 sera, both antitoxic and bactericidal, do not lend support to this 

 assumption, since thus far we know age merely to weaken the sera 

 but not to increase the antitoxic action. It is more natural, there- 

 fore, to assume that the serum contains substances which act like 

 negative catalyzers. Thus, while the positive catalyzers already 

 mentioned hasten the toxin-antitoxin reaction, the negative cata- 

 lyzers assumed to exist in the serum would retard the tightening 

 of the union. One would then say that the fresh antiarachnolysin 

 serum contained the negative catalyzer, and that this by retarding 

 the tightening of the union, made possible the dissociation of the 

 two components when the mixtures were diluted. In an old serum, 

 on the other hand, this retarding substance would be absent, thus 

 making the toxin-antitoxin union firm in a very short time. In 

 that case, of course, the dilution phenomenon could not be demon- 

 strated. 



We believe that a mere study of the successive events in the 

 toxin-antitoxin neutralization permits of no direct conclusions. We 

 have seen that it is impossible to exclude certain factors which 

 markedly affect the course of the reaction; the existence of positive 

 catalyzers had necessarily to be assumed, and the influence of nega- 

 tive catalyzers was rendered probable by the results of our investi- 

 gations. It is therefore impossible by a mere numerical analysis of 

 the course of the experiment to draw definite conclusions concerning 

 the absolute combining affinity in the toxin-antitoxin reaction. 



