THE CONSTITUENTS OF DIPHTHERIA TOXIN. 499 



Madsen, too, has described a poison "C," the constitution of 

 which is very interesting because prototoxoid and pure toxin are 

 distinctly marked off from one another. During the phase at which 

 Madsen examined it the pure toxin zone occupied the zone 50 to 100 

 of the spectrum. Before the formation of tritotoxoid this zone may, 

 however, have extended to 150. 



From these observations we see that for certain portions of the 

 spectrum (which lie in the middle and not at the commencement 1 ) 



it has been possible to prove that -p^-z. I. E. combines with exactly 



1 L. D. This argues strongly in favor of the correctness of my 

 assumed figure 200. In these zones of pure toxin only toxin molecules 

 are neutralized and no toxoids. 



Although it is rare to find zones of pure toxin in poisons which have 

 been kept some time, it is extremely common, or even constant, to- 



find in these older poisons zones in which =: I. E. neutralizes exactly 



J L. D. Manifestly under these conditions equal parts of toxin and 

 toxoid must always be neutralized; for this reason I have termed 

 such a poison a hemi toxin. The following scheme represents such a 

 changed poison: 



T 



TT 



Toxin : Pure Toxin 



Toxoid: Hemitoxin 



FIG, 3. 



It needs no further explanation to show that in this hemitoxin 

 zone the affinity of toxin and toxoid to antitoxin has remained un- 

 changed. 



The entire process of toxoid formation takes place in two phases, 

 as can readily be seen from the initial zones of suitable spectra (see 

 Fig. 3). The pure toxin first changes into hemitoxin; in the second 

 phase, however, the hemitoxin changes into pure toxoid, especially 

 in the first part of the spectrum. This is illustrated by the following 

 scheme : 



1 In the curve of ammonia-boric acid and of tetanolysin the maximum 

 combining power always occupies the very first portions of the curve. 



