THE ANTIBEKIBEEI VITAMINE 165 



may provide an answer for the question as to which fraction contains 

 the vitamine. It sometimes takes weeks before we are certain of 

 this, and during this time the fractions obtained must await further 

 manipulations. The means used till now for the study of the nature 

 of the vitamines (almost exclusively the more stable vitamine B) 

 are as follows : 



1. Fractionation of the active material according to the known 

 methods. 



2. Attempts to separate the active material by solubility and 

 selective adsorption. 



3. Testing of vitamine-like action of combinations of known or 

 unknown composition. 



4. Synthetic experiments with substances obtained in vitamine 

 work. 



Up to the present, none of these four procedures has yielded very 

 substantial results, although the first of these methods, which is 

 most direct, has been productive of the most instructive findings. 

 By this means, some precipitation reactions have been found which 

 lead to a vitamine fraction which appears to be quite simple in com- 

 parison with the complexity of the starting material. From these 

 fractions, there have been isolated well defined substances which 

 possess a very marked curative action while in the impure state, but 

 which, upon further purification, lose much if not all of their activity. 

 Nevertheless, it has been possible to isolate a substance that has been 

 crystallized to constant melting point, at the same time retaining a good 

 deal of its activity; this was the case with our work on yeast. How- 

 ever, the objection is justified that the vitamine is present in 

 such a small quantity that it has no effect on the melting point. We 

 must determine now whether we are dealing with inactive material 

 that has adsorbed the vitamine, or with one or more cleavage prod- 

 ucts serving as the inactive basic structure for the vitamines. It is 

 obviously very unlikely that the vitamines should disappear without 

 leaving a trace. When radium, for example, undergoes complete 

 decomposition, the end product is inactive lead. It is not impossible 

 that in vitamines we encounter a similar problem. Our view is 

 further strengthened in this respect when amongst the substances 

 usually accompanying vitamine B, we constantly meet with products, 

 having the pyridine ring, which has been recognized as a cell con- 

 stituent for the first time in vitamine work. If we were certain 



