TOXINS AND ANTITOXINS 209 



stantly decreasing (by reason of toxoid formation), L + remained 

 practically unchanged. 



Simply stated, this means that the epitoxoids or substances which 

 have weaker affinity for antitoxin than toxin itself are already present 

 in fresh bouillon and are not increased with time. For this reason, 

 Ehrlich has separated these substances from toxoids. He calls them " tox- 

 on " and believes them to be, like toxin, primary secretory products of 

 the diphtheria bacilli. The toxoids themselves, Ehrlich believes, are of 

 two kinds, those with a stronger affinity for antitoxin than toxin it- 

 self (protoxoids), and those whose affinity for antitoxin is equal to that 

 of toxin. These latter he calls "syntoxoids." 



The toxon (epitoxoid originally), as Ehrlich believes, has a hapto- 

 phore or " binding" group similar to that of toxin, but a different 

 toxophore or " poisoning" group. Qualitatively it has been shown 

 to differ from toxin in that, lacking the power to produce acute symp- 

 toms, it causes gradual emaciation and paresis in animals. 



That this difference in the poisonous action of toxin and toxon 

 is not merely a quantitative difference, referable to small quantities of 

 toxin, was proved by Dreyer and Madsen, 1 who showed that if they made 

 a toxin-antitoxin mixture in which after injection the only evidence of 

 incomplete neutralization lay in the emaciation and final paralysis of 

 the test animals, the quantity of such a mixture could be increased 

 five- and tenfold, without producing the true toxin symptoms in ani- 

 mals. These authors, too, claim to have been able to immunize against 

 toxin with such mixtures, thereby proving the identity of the haptophore 

 groups of the two substances. The importance of this observation will 

 become more evident in connection with the section on the "side- 

 chain theory." 



METHOD OF PARTIAL ABSORPTION OF TOXIN. Ehrlich 2 has gathered 

 more exact data in support of his views from what he terms the " Method 

 of Partial Absorption " of toxin by antitoxin. 



In order to understand this method clearly, it is necessary to re- 

 member that Ehrlich 3 believes the union of toxin with antitoxin to 

 take place according to the chemical laws of valency. Just as in H 2 O 

 oxygen has an atomic valency of 2 for hydrogen, so, in the fully 

 neutralized toxin-antitoxin compound, he believes antitoxin to have a 



1 Dreyer iind Madsen, Zeit. f. Hyg., xxxvii, 1901. 



2 Ehrlich, " Gesammelte Arbeiten zur Immunitatsforsch.," Berlin, 1904. 

 s Ehrlich, Deut. med. Woch., 1898. 



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