The Cerebrosides of Brain Tissue. 95 



It was found that the benzoyl derivative of phrenosin was more 

 insoluble in methyl alcohol, than that of kerasin. Indeed, by 

 preparing the benzoyl derivative of a mixture with a rotation of 

 ± 0.0 (in pyridine) one could separate this into two fractions, 

 the more soluble of which had a rotation of — 2.25 to 3.2 0 , varying 

 in different experiments. These rotations refer not to the benzoyl 

 derivatives, but to the cerebrosides obtained after saponification 

 of the acyl derivative. The substance with the highest levorota- 

 tion (— 3.28 0 ) obtained in this way corresponded to the one named 

 by Rosenheim pure kerasin and the one we had in hand several 

 years ago. Since that time the methods of hydrolysis have been 

 improved; applying this for the analysis of new material, we 

 again found that the fatty acid fraction contained both lignoceric 

 and cerebronic acids. On the basis of this, we confirmed our 

 original view that so-called kerasin has not yet been obtained in 

 the pure state. On the other hand, the very gratifying results 

 obtained by the benzoyl method carries confidence in the possi- 

 bility of a successful separation of kerasin by repeated benzoylation 

 of the levorotatory fraction of cerebrosides. The work in this 

 direction will be undertaken as soon as a sufficient quantity of the 

 cerebroside mixture will be prepared. 



We wish to refer briefly at this place also to the problem of 

 the sugar contents of cerebrosides. On the basis of the present 

 assumption and their structure, the theory requires a value of 

 20 per cent. Employing Thudichum's method of hydrolysis 

 Rosenheim reports a theoretical yield of sugar. This first seems 

 mysterious to us. Control experiments on pure galactose carried 

 out in our laboratory by G. M. Meyer showed that the sugar 

 subjected to the treatment employed by Thudichum, Rosenheim 

 and others suffered a very considerable destruction. Indeed, in 

 the early part of the work, we could never obtain the required 

 20 per cent. For a time this seemed to be in the way of accepting 

 the conventional theory of the structure of the cerebrosides. 

 However, conditions of hydrolysis have been perfected in which 

 the sugar undergoes little decomposition, and under such condi- 

 tions the yield of sugar is as the theory requires, about 20 per cent. 



