On Protagon 107 



Until this question can be decided conclusively, either one way or the 

 other, an objective interpretation of the known facts must be sufficient. 



We have emphasised already the fact that protagon has a definite 

 chemical composition and retains this composition after repeated recrystal- 

 lisation. This substance has been obtained by various observers and by 

 various methods. As we have pointed out in a former communication, this 

 fact is evidence in favour of the view that protagon is a definite chemical 

 compound. To this evidence we add further the fact of the constancy of 

 its physical properties. The crystalline form of protagon we have never 

 considered to be of much value in recognising the nature of protagon, as it 

 is well known that mixtures of complex organic compounds frequently 

 crystallise out together in a definite crj^stalline form. The weight of the 

 analytical evidence has been admitted even by those who hold different 

 views on the nature of protagon. Lesem and Gies discuss their analytical 

 results of four samples of protagon as follows : " Much to our surprise, these 

 results accord as well as many analytical series given for what are un- 

 doubtedly individual substances. Our data in this connection, considered by 

 themselves, would seem to harmonise with the older view of the integrity 

 of protagon." 



Against this \aew the results of the so-called process of fractional 

 crystallisation have been adduced as demonstrating that protagon is a 

 mixture of substances differing widely in their solubility, differing widely in 

 their chemical composition and constitution, and in their physical constants. 

 These results appear in a new light, since we have been able to prove that 

 they are due to a factor which has not been recognised before, namely, the 

 instability of protagon towards warm alcohol. This fact changes the 

 process of fractional recrystallisation into one of partial decomposition, 

 and invalidates the conclusions which have been drawn from these 

 experiments. 



This property of protagon is responsible for the fact that, bj- following 

 known methods for the preparation of protagon, substances have been 

 extracted from brain which differ from protagon in their chemical com- 

 position. By calling all the substances protagon which were prepared 

 according to an acknowledged method, these results have been used as 

 additional evidence for the variability of the protagon mixture. In the 

 only case in which the account of the technique employed was detailed 

 enough to repeat the process, it was possible to show that the failure to 

 obtain protagon was due to the prolonged treatment with warm alcohol. 



Not only is it incorrect to interpret these results as evidence against 

 the existence of protagon, but we must protest against such reasoning, 

 which threatens to deprive the protagon problem of its very basis. What- 

 ever protagon is, the name protagon has been given to a substance of a 

 definite chemical composition, having, as we have seen, definite physical 

 constants. Like every other chemical substance, protagon is identified by 

 these properties and not by its method of preparation. Many of the 



