ACTION OF ANTITOXINS ON TOXINS. 267 



toxin molecules are not monopolized by certain of the toxin mole- 

 cules, whose affinities become thereby satisfied, leaving the remain- 

 ing toxic units intact. On the contrary, the antitoxin molecules 

 are shared by and divided equally among all the toxic molecules 

 present, which thenceforth are partially saturated and lose to a 

 certain extent their original toxicity. 



2. The phenomena of intoxication caused by injecting this 

 compound into animals may not be the same as those produced 

 by a mixture of neutralized toxin plus intact toxin. 



3. Between the extremes of free toxin and entirely saturated 

 or innocuous toxin, all transitions or stages of progressive attenua- 

 tion may exist. Each time that a mixture of toxin and antitoxin 

 is made in a given relation the same degree of attenuation will be 

 produced. 



Ehrlich, as we know, interprets his phenomenon in quite a dif- 

 ferent way. He thinks that toxin and antitoxin unite in fixed pro- 

 portions. To harmonize his phenomenon with the law of fixed 

 proportions, Ehrlich makes the supposition that the composition 

 of toxic bouillon is very complex; that it contains, indeed, several 

 poisons: one, an active poison, is the toxin properly speaking; 

 another, less dangerous poison, is the toxon. 



A molecule of toxin absorbs as much antitoxin as does a mole- 

 cule of toxon. In this respect the two substances are equivalent. 

 But the toxin exceeds the toxon in the energy of its affinity for, 

 or in other words is more avid of, antitoxin. In order to neutralize 

 completely a toxic bouillon enough antitoxin must be added to 

 neutralize both toxin and toxon. But if an additional amount of 

 toxic bouillon is added, the additional toxin that it contains will 

 seize antitoxin that has already combined with the original toxon, 

 and so liberate this latter substance. In other words, if to 

 antitoxin a few doses of toxin in excess of the proper amount 

 for neutrality are added to obtain a fluid containing no free 

 toxin, there is, to be sure, uncombined toxon; but since this is 

 relatively harmless the animal withstands the injection of such a 

 mixture. 



As a matter of fact we have simplified this explanation con- 

 siderably, for Ehrlich has attributed an extraordinarily complicated 

 composition to the toxic bouillon in order to make his theory agree 



