DIPHTHERIA BACILLUS. 363 



the antitoxin strength increases. It seems, therefore, 

 from the above facts that diphtheria antitoxin has the 

 characteristics of the globulins. Whether it is a union 

 of diphtheria toxin and globulin, or an increase of cer- 

 tain globulin-like substances through the stimulation of 

 the toxin, we have as yet no facts to tell us. Antitoxin 

 is destroyed by prolonged moderate heat (60 C.) and 

 by short exposure to higher temperatures (95 to 100 

 C.). It is much less sensitive than diphtheria toxin. 



Diphtheria antitoxin has the power of neutralizing 

 diphtheria toxin, so that when a certain amount is in- 

 jected into an animal before or together with the toxin 

 it overcomes its poisonous action. As already stated, 

 there is a great difference of opinion as to whether anti- 

 toxin acts by direct chemical neutralization of the toxin 

 or indirectly on the cells. The facts in favor of a direct 

 action of antitoxins upon their corresponding toxins 

 have recently been briefly summarized by Cobbett as 

 follows : 



1. Certain reactions have been observed to take 

 place between these substances outside the animal body 

 (venom, ricln, crotin, tetanus toxin, diphtheria toxin, 

 and their corresponding antitoxins). 



2. Various attempts to separate the toxins and anti- 

 toxins from neutral mixtures have been failures. Par- 

 tial successes have, at least in some instances, been 

 shown to depend upon the fact that insufficient time for 

 their complete union was allowed, separation being no 

 longer possible if this were granted. 



3. The accuracy of the titration of toxins and anti- 

 toxins to within 1 per cent, of error. 



4. The fact that to save an animal from 1000 fatal 

 doses of diphtheria toxin requires little more than a 



