500 COLLECTED STUDIES IN IMMUNITY. 



/\ I : Pure Toxin 



Toxin / 



V 



T 



Toxoid. 



: Hemitoxin (Hemi- 

 toxoid). 



: Pure Toxin 



FIG. 4. 



I must again emphasize that this sketch of the decomposition 

 of the poison is not at all hypothetical, but merely the expression 

 of the facts observed. The regular course in two phases points di- 

 rectly to the fact that the individual toxins are not simple uniform 

 substances but are composed of two modifications present in equal 

 amounts in the toxin solution and behaving differently on decompo- 

 sition. One, the more unstable of the two, the ct-modification, decom- 

 poses rapidly and so gives rise to the stage of hemitoxin. The subse- 

 quent destruction of the more stable /^-modification leads to pure 

 toxoid. It is, of course, somewhat remarkable that exactly equal 

 parts of two toxin modifications should develop in diphtheria bouillon. 

 This is readily understood, however, if we remember that E. Fischer 

 has made it extremely probable that the active groups of ferments 

 (groups exhibiting a great similarity with the toxophore group) pos- 

 sess an asymmetrical constitution. If then in accordance with this 

 we assume an asymmetrical constitution of the toxophore group, there 

 will be nothing remarkable in the fact that the diphtheria bacilli 

 produce both asymmetrical components simultaneously. Nor is it 

 surprising that both are produced in equal amounts if we consider, 

 for example, that optically inactive tartaric acid consists of equal 

 parts of dextro and Isevo tartaric acid. If optically active combina- 

 tions (of which a large number can be made artificially) are produced 

 in the retort, the rule holds that exactly the same number of mole- 

 cules of the two components are produced by the reaction. 



Ever since Pasteur showed that in the fermentation of tartaric 

 acid by moulds the dextro tartaric acid is decomposed first, it has been 

 found possible to demonstrate a similar behavior in numerous other 

 instances ; thus by the aid of moulds, yeasts, and bacteria it was found 

 possible to isolate one of the optically active components from racemic 



