102 Wilson and Cramer 



failure of some workers to isolate protagon from brain be considered as 

 evidence against its existence, seeing that other workers have obtained this 

 substance without difficulty. If we exclude all these observations, there are 

 still a number of experiments which show that, by means of a certain 

 process, which has been called a "process of fractional crystallisation," 

 protagon is split up into substances varying widely in their phosphorus 

 percentage and in their solubility in alcohol and ether. This was demon- 

 strated conclusively by Gies and his collaborators. In a former paper by 

 one of us it was suggested that the protagon of Lesem and Gies may have 

 been contaminated with pseudocerebrin. But as the analytical figures of 

 their preparations are identical with those of Gam gee's protagon, their 

 material must be considered as representing typical protagon, and Posner 

 and Gies are right in contending that, if their preparations were con- 

 taminated with pseudocerebrin, the same may be said of Gam gee's and 

 Cramer's protagon. In order to remove any possible objection, Posner 

 and Gies have recrystallised protagon ten times until the phosphorus 

 percentage of the crystalline product and of the mother liquid was almost 

 the same and identical with that of protagon. Even from this preparation 

 different substances could be isolated when the so-called process of fractional 

 crystallisation was applied. 



This process consists in the treatment of protagon with a quantity of 

 warm alcohol, insufficient to dissolve it, over periods lasting many hours 

 (20-24 hours). After separating the soluble from the insoluble part, the 

 solution is allowed to cool slowly, and the substances crystallising out at 

 different temperatures are collected separately and then show the differences 

 mentioned above. 



Of the correctness of these facts there can be no doubt ; it is only in 

 their interpretation that we differ from Gies and his collaborators. In 

 order to interpret these facts as proving conclusively the composite nature 

 of protagon, it is of course essential that the prolonged treatment with 

 warm alcohol does not effect any change in the protagon — in other words, 

 that the process is really one of recrystallisation and not one of decomposition. 

 This last possibility has, indeed, been considered by Lesem and Gies, who, 

 is speaking of their results of fractional crystallisation, say : " They show 

 that protagon is either a mixture of bodies or else a substance decomposing 

 quite readily under the conditions of such experiments." Rosenheim and 

 Tebb simply dismiss the second possibility by saying that the process of 

 fractional crystallisation evidently cannot effect any serious chemical 

 decomposition. A priori there is no reason why these results should not 

 prove with equal force that the prolonged treatment with warm alcohol has 

 induced a decomposition. Before the treatment protagon is, as we have 

 seen, a substance of a constant composition retaining this composition after 

 simple recrystallisation, which involves only a short contact with warm 

 or boiling alcohol, the mother liquor and the crystalline product having an 

 almost identical phosphorus percentage : in the course of its preparation it 



