DIPHTHERIA BACILLUS. 371 



dose. Later, with the period of cessation of toxin pro- 

 duction, the gradual deterioration of the toxicity alone 

 continues, and the fatal dose gradually and steadily in- 

 creases in its neutralizing value. 



Ehrlich's theories as to the splitting up of " toxin" 

 into toxoids having little or no toxicity, but on the 

 average full neutralizing power for antitoxin have 

 not, in our opinion, been substantiated by the results 

 of these experiments. The difference between the 

 amount of toxin mixed with a unit of antitoxin which 

 causes the first symptoms and that causing death upon 

 the fourth day would be, it is true, explained by his 

 theory; but the failure of this difference to be greater 

 where, by his theories, epitoxoids should be in great 

 abundance, prevents our acceptance of his views. The 

 fact of the greater neutralization value of a fatal dose 

 of a deteriorated toxin would be accounted for on his 

 protoxoid theory. This, however, is not proof of its 

 correctness, as other theories, such as the production by 

 the diphtheria bacillus of two or more closely allied 

 toxins, similar to the allied alkaloids produced by 

 plants, would equally account for it if we supposed 

 the one which had the greater neutralization value was 

 more resistant to destruction than the other. 1 We only 

 advance this theory to call attention to the fact that 

 many theories can on paper explain a process without 

 necessarily being thereby established. 



While we do not believe, therefore, that he has 

 changed the principles of testing antitoxin, yet we 

 believe he has contributed greatly to uniformity in 

 results by calling attention to the necessity of selecting 



1 The incomplete precipitation of the diphtheria toxin by MgSO 4 makes it 

 probable that more than one poison exists. 



