192 INFECTION AND IMMUNITY. 



stroyed by the antitoxin the solution certainly 

 would not have regained its original toxicity on 

 the application of heat. 

 chemical The following facts add support to the view 



^tVjTction? that neutralization consists of chemical union be- 

 tween the two substances : 



First, neutralization takes place according to 

 the law of multiple proportions, i. e., ten times a 

 given amount of antitoxin will neutralize a pro- 

 portionate amount of toxin; second, neutralization 

 is more rapid at warm than at cold temperatures; 

 and, third, more rapid in concentrated than in di- 

 lute solutions. These are some well-known laws of 

 chemical reactions. 



Ferments. "Emil Fischer has shown that in the ferments, 

 definite atom-groups of special configuration are 

 present which above all else are requisite for the 

 whole phenomenon (of fermentation). Only such 

 substances as possess a group to which the ferment 

 group corresponds, as lock to key, are subject to 

 the action of a particular ferment." This applies 

 to the action of a particular ferment on only one 

 kind of substance. 



Having this conception in mind, Ehrlich as- 

 sumes that union occurs between toxin and anti- 

 toxin through a special group of atoms which the 

 toxin molecule possesses, and which fits into, or 

 corresponds specifically to, another group of atoms 

 in the antitoxin molecule. These are spoken of 

 as the binding or haptophorous groups (hapto- 

 phores) of the molecules. The haptophorous 

 group of the toxin molecule is highly specific since 

 a toxin can be neutralized only by its 'own anti- 

 toxin, and naturally the haptophorrous group of 

 the antitoxin molecule must be equally specific. 



