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MANUAL OF BACTERIOLOGY. 



solution of several different but related bodies, and he makes so-called "spectra" 

 to explain this idea. He thinks that primarily the substances are toxin and 

 toxon (Fig. 53), each having affinity for antitoxin; but the affinity of toxon for 

 antitoxin is weaker than the affinity of toxin for the antitoxin. And, further- 

 more, toxon no matter in what dose does not kill guinea-pigs quickly if at 

 all, but causes a paralysis of the animal some weeks after inoculation, while 

 toxin, on the other hand, in just the proper amount kills a guinea-pig weighing 

 250 grams in two days. This is the standard minimum fatal dose, or i d. 1. 

 (dosis letalis). 



Now, if enough antitoxin is added to the poisonous beef-broth it will neutral- 

 ize both the toxin and the toxon, but if not enough is added for this, the toxin 

 is first neutralized and the toxon still produces paralysis of the guinea-pig. 



But on standing, both toxin and toxon quickly become changed; a part of the 

 toxin is converted into a body called toxoid and a part of the toxon into toxonoid, 

 and, while retaining their affinity for antitoxin, these are both weakened in patho- 

 genic power as compared with the original toxin; toxoid, in fact, is devoid of 

 toxic properties. Toxoid, then, is toxin deprived of its toxophore, but it retains 



Tox.on. 



200 



FIG. 53. "Spectrum" of theoretically fresh, crude toxin. 

 Such a combination probably does not occur. 



the haptophore group. Still further, the resulting toxoid and the toxon have 

 each three different degrees of affinity for antitoxin. 



A part of the toxoid has less affinity than the toxin; a part equal; a part more. 

 These are designated epitoxoids, syntoxoids and protoxoids, respectively (Figs. 

 54 and 55), and toxons are in like manner designated epitoxons, syntoxons and 

 protoxons. But, since all toxons have less affinity for antitoxin 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 (too 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 

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

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



