TOXINS AND ANTITOXINS 261 



Thus, in analyzing our example, we have : 



100 tox.-antitox. + 100 epitox.-antitox. L Q ; 



add 1 T,and we have 101 tox.-antitox.-f99 epitoxoid-antitoxin+1 epitoxoid free ; 

 add 101 T and we have 200 toxin-antitoxin +100 epitoxoid free + 1 T free= I + - 



Two facts, however, led Ehrlich to abandon the opinion that 

 epitoxoid was merely a variety of toxoid. He found, in the first 

 place, that the stated relations between L and L + were true for 

 perfectly, fresh toxin-bouillon in which little or no deterioration 

 had taken place. He observed, furthermore, that in old, altered 

 toxin bouillon, while T was very much affected, the quantity needed 

 to kill a pig constantly increasing, and the number of actual fatal 

 doses in L constantly 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 "toxon" 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 itself (protoxoids), and those whose affinity 

 for antitoxin is equal to that of toxin. These latter he calls "syn- 

 toxoids. ' ' 



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

 haptophore or " binding" group similar to that of toxin, but a dif- 

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

 shown to differ from toxin in that, lacking the power to produce 

 acute symptoms, 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, 16 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 animals. These authors, too, claim to have been 



18 Dreyer mid Madsen, Zeit. f . Hyg., xxxvii, 1901. 



