TOXIN AND ANTITOXIN: METHODS OF THEIR STUDY. 553 



rise and fall of the differential quotients shows at once that a hyper- 

 bolic curve is out of the question in the case pictured above. If 

 we examine the poison spectrum, on the other hand, we find that this 

 represents Madsen's poison entirely in accord with Ehrlich's views 

 concerning the constitution of diphtheria poison. If toxin and anti- 

 toxin unite firmly, and the course of the neutralization curve there- 

 fore is a straight line, the irregular course is explained by the toxoid 

 present in the poison and by the varying affinity of the poison con- 

 stituents The highest zone in the poison spectrum (zone c) indicates 

 that at this point equal amounts of antitoxin cause the greatest 



FIG. 1. Poison spectrum according to Ehrlich. 



decrease in toxicity. Hence this part of the poison must contain 

 the least toxoids, or none at all, and we may therefore speak of this 

 as pure toxin. It will serve as a unit for judging the degree of con- 

 tamination with toxoid in the remaining portions. We should then 

 speak of zone b as the hemitoxin, i.e., for each molecule of toxin 

 there is one of toxoid. The sequence of the different zones corre- 

 sponds to the different affinities of the components. Thus we see 

 that the addition of a small amount of antitoxin (a) does not cause 

 any decrease of toxicity whatever. And yet the antitoxin must 

 have been bound. We conclude, therefore, that toxoids must here 

 be present which possess a higher affinity than any other constituent 

 of the poison. We are here dealing with the important prototoxoid 

 zone which we encounter so frequently in diphtheria poison, abrin, 

 ricin, crotin, etc. The hemitoxin zone which follows this is to be 

 regarded as a deutero toxin in its affinity. The constituents of the 



