498 



COLLECTED STUDIES IN IMMUNITY 



tophore group suffers a decrease in affinity. Complementoids, it will 

 be remembered, result from the destruction of the zymotoxic group, 

 the analogue of the toxophore group. Eisenberg and Volk by their 

 discovery of proagglutinoids have shown that in the formation of 

 agglutinoids an increase in affinity can take place. 



Hence in diphtheria poison the possibility had to be considered 

 that similar conditions obtain in toxoid transformation. In this case, 

 however, it was remarkable that this toxoid formation did not always 

 follow the same scheme, the poison, of course, always being thought 

 of as a simple uniform substance. I was finally able to solve this 

 problem in the following manner. 



My earlier investigations had given me the impression that 1 I. E. 

 (immune unit) should neutralize 200 fatal doses of a pure toxin, one 

 consisting only of toxin molecules and therefore free from toxoids. 

 I am quite ready to admit that I did not at that time furnish any 

 absolute proof for this view. My first effort was therefore directed 

 to a study concerning the correctness of the figure 200. I began by 

 analyzing a large number of different toxins in the hope that sooner 

 or later I would find an ideally pure toxin. I have already men- 

 tioned that the highest purity thus far obtained, a toxin obtained 

 by Madsen, corresponds to only four-fifths purity, L t containing 160 

 L. D. Nevertheless by means of the method of neutralization I was 

 able to find poisons which fulfilled my requirements, at least in part. 

 This was the case, for example, in my Poison No. 2 (see spectrum, 

 Fig. 2). In this the L dose contained 84 L. D. The first third of the 



10 20 30 40 50 CO 70 80 90 100 110 120 130 140 150 .160 .170 180 190 200 



FIG. 2. 



spectrum was taken up by a zone of hemi toxin not quite pure, i.e., each 



combining unit added 



200 



I. E. 



decreased the toxicity by about 



& 



L. D. In the next zone, on the other hand, stretching from 72 to 115, 

 each combining unit took away exactly 1 L. D. The spectrum is 

 here reproduced. It shows the zones of hemitoxin, pure toxin, trito- 

 toxoid, and toxon very clearly. 



