IMMUNITY. 



189 



syntoxons and protoxons. But, since all toxons have less aflSnity for anti- 

 toxin than toxin has, it follows that epitoxoid and toxon are the same. All crude 

 toxin, then, is composed of a mixture of toxin, toxoid and toxon, for toxoids 

 begin to form immediately, so that toxin-toxon without toxoid is not known. 

 When enough antitoxin is added to 100 doses (100 d. l.'s) of crude toxin 

 to just neutralize it, all the toxin and all the toxon are united to antitoxin. But 

 if fresh toxin is added, some of the toxoid and toxon is liberated, and the added 

 toxin becomes attached to the antitoxin in its place; and so with each additional 



ProioKoid 



Toxon. 



60 'to ZOO 



Fig. 52. — "Spectrum" of Very Fresh Crude Toxin. 



amount of toxin added more toxon and toxoid is liberated tiU the point is reached 

 where all the toxon and toxoid is free, and the additional toxin finds all the 

 haptophores of antitoxin occupied by the toxin previously added. In this case 

 any additional toxin remains uncombined, and, if such a mixture is injected 

 into a guinea-pig, the animal is killed. 



'ProtoKoid 



Synloxoid 



60 



V////////////// 

 '/// //emitoxin yy//\ 



Ti/xan. 



160 



200 



Fig. 53. — "Spectrum" of Crude Toxin as it is Supposed Practically 

 Always to Occur. 



Bordet's* explanation differs from Ehrlich's. Bordet does not admit the 

 existence of toxons, and regards the paralysis attributed by EhrUch to the 

 action of this hypothetical substance as due to weakened toxin. He explains 

 the peculiar behavior of a neutralized mixture of crude toxin with antitoxin, 

 stated above, by assuming that antitoxin is capable of taking up and neutralizing 

 varying amounts of toxin. He compares the effect of mixing toxin and anti- 

 toxin to that of mixing starch and iodine : the more iodine added to the starch. 



* Bordet. Toxines et Antitoxines. 

 Pp. 161 et seq. 



Annates de I'Inslitut Pasteur. 



1903. 



