108 Wilson and Cramer 



substances which figure in recent papers as protagon have no claim to this 

 name. 



There is therefore no evidence in favour of the view ofThudichum and 

 his followers that protagon is a mixture of substances differing from each 

 other in almost every respect. On the contrary, we must conclude that 

 the substances found after the prolonged treatment with warm alcohol are, 

 besides unchanged protagon, decomposition products of protagon. One of 

 these decomposition products, the phosphorus free phrenosin (cerebron, 

 pseudocerebrin), has indeed been found to be identical with cerebrin, which 

 is obtained by hydrolysing protagon by baryta water. The phosphorised 

 moiety of the protagon molecule, however, does not behave in the same way 

 towards warm alcohol and towards baryta. This last reagent carries the 

 hydrolysis to the ultimate constituents; of which choline, sphingosine, 

 glycerophosphoric acid and fatty acids have been isolated. The action of 

 alcohol does not go so far. This is quite clear from the investigations of 

 Thudichum, who isolated numerous substances from brain by methods 

 involving prolonged extraction with boiling alcohol and distillation of the 

 alcoholic solutions regardless of any decomposition. These substances w^ere 

 hydrolysed further by means of baryta water. The treatment with warm 

 alcohol, instead of being a means of separating the substances which are 

 present in the mixture protagon, would appear therefore to be a useful 

 method for the study of the more complex groups which enter into the 

 composition of the compound protagon. 



Seen in this light, the observations of Gies and of Rosenheim and 

 Tebb, so far from being opposed to the view that protagon is a definite 

 compound, are a valuable contribution to the study of the constitution of 

 this substance. 



The question has also to be considered whether the substances which 

 have been isolated from brain, and which at the same time have been 

 isolated from protagon hydrolysed by alcohol, such as, for instance, phrenosin 

 (pseudocerebrin, cerebrin, cerebron), exist preformed in the brain or are 

 formed only in the process of extraction. 



Although our results support the view that protagon is a definite 

 compound, we do not exclude the possibility, which has been considered 

 already in a former paper, that several protagons exist just as several 

 lecithins exist. The existence of such substances, differing perhaps only 

 in the nature of the fatty acid radicle which they contain, would be no 

 more evidence against the existence of protagon than the existence of 

 several lecithins is considered to disprove the existence of a definite 

 compound lecithin. Such protagons would be distinguished only by slight 

 differences in the carbon and hydrogen contents, and would resemble each 

 other very closely in every respect, so that they could not be separated 

 easily. It is therefore possible that protagon is a mixture of such sub- 

 stances, although there is at present no evidence for it. Such a view, which 

 is quite compatible with the idea that protagon is a definite compound, is 



