36 INFECTION AND RESISTANCE 



the original filtrate, or its antitoxin-inducing power. Concerning 

 the methods which have been employed in the study of the chemistry 

 of these substances we will have more to say in another place. 23 It 

 is safe to summarize all this work for our present purposes, by stat- 

 ing that, whatever the method employed, until now all of the prep- 

 arations obtained have given one or another of the protein type- 

 reactions, and that none of them can be positively accepted as pro- 

 tein-free. The results here obtained have been entirely analogous to 

 those obtained in similar investigations upon enzymes. (See also 

 discussion of antigens, chapter 4.) 



The analogy with enzymes is indeed a striking one and noted by 

 the first investigators of a true toxin, Roux and Yersin. Biolog- 

 ically, of course, we have the cardinal similarity in that the injec- 

 tion of toxins into animals induces the production of antitoxin, and 

 treatment with enzymes induces specific and neutralizing anti-en- 

 zymes. In addition to this, they are alike in their susceptibility to 

 heat (both being destroyed when in solution by temperatures over 

 80 C.), in their gradual deterioration on standing, and their mys- 

 terious activity in small quantities upon disproportionately larger 

 masses of the substances they attack. There is, however, one impor- 

 tant difference between the two in their mode of action. For, while 

 the toxins are apparently bound or neutralized by the tissues they 

 attack, the action of an enzyme seems rather to be a process in which 

 the enzyme unites with the substance it acts upon, is released as the 

 result is attained, and freed for further action, without noticeable 

 loss of quantity. Such catalytic properties have not yet been satis- 

 factorily demonstrated for the bacterial toxins. However, there are 

 other modifying factors which may account for lack of similarity in 

 this respect, and in all other important points the two classes of sub- 

 stances are closely analogous. 



The property of heat sensitiveness, which is a characteristic of 

 bacterial exotoxins and enzymes, is shared with them by all of the 

 substances mentioned above except snake venoms. Snake venoms 

 are not destroyed completely until the temperature is raised to 75- 

 80 C. The earlier contention of Leclainche and Vallee, that the 

 toxin of symptomatic anthrax possessed similar heat stability has 

 been satisfactorily refuted by Grassberger and Schattenfroh, 24 who 

 find that heating it to 50 C. for an hour completely destroys it. 



There is another important attribute of the true toxin which 

 deserves discussion, though we are by no means in a position to offer 

 any satisfactory explanation for it. We refer to the incubation time 

 which elapses between the administration of a toxin and the occur- 



23 An extensive and authoritative summary of this phase of the subject is 

 that of E. Pick in "Kolle u. Wassermann Handbuch," etc., 2d ed., Vol. 1. 



24 Grassberger and Schattenfroh. "Tiber das Rauschbrandgift, etc., 1 '' 

 Wien. Deuticke, 1904. 



