THE CONSTITUENTS OF DIPHTHERIA TOXIN 



501 



combinations. Looked at in this way the formation of hemitoxin is 

 explained in very simple fashion. 1 



It can readily be shown that in the first stage of toxoid formation 

 which leads to hemitoxin no change in affinity takes place, and this 

 holds true also for all the toxoid formation, for if an increase in 

 affinity occurred there could be no hemitoxin zone ; a prototoxoid 

 zone would again be followed by a zone of pure toxin. Conversely 

 if there were a decrease in affinity a zone of pure toxin would precede 

 the toxoid portion. The following scheme will serve to make these 

 conditions clear: 



These considerations 

 at once show us that in 

 the formation of toxoid 

 no change in affinity can 

 take place. As a matter 

 of fact, however, the pro- 

 totoxoid possesses a much 

 stronger, and the trito- 

 toxoid a much weaker, 

 affinity than the toxin or 

 hemitoxin occupying the 

 central portion of the 



spectrum. This we saw in our analysis of the poison mentioned 

 above. We must, therefore, conclude that this difference is not 

 produced by the formation of toxoid, but exists in the toxic bouil- 

 lon from the beginning, the initial portion of toxin, which subse- 

 quently passes over into prototoxoid, already possessing a higher 

 affinity for the antitoxin. The poison of diphtheria, for example, 

 could be represented by the following rough diagram, in which the 

 degree of affinity is expressed schematically by the length of the lines : 



TTTT 



i i 



Tl 

 T I 



FIG 5. 



Pure Toxin 



Increased 

 Affinity 



Decreased 

 Affinity 



Affinity 

 Unchanged 



1 See E. Fischer. Zeitschr. f. physiol. Chemie, Vol. 26. 



