THE CEREBRINS OR CEREBROSIDES. 119 



The percentage composition is seen in the following table : 



An elaborate research by Thudichum l led him to the conclusion that 

 there are three groups of phosphorised substances in the brain, which he 

 termed kephalines (very soluble in ether), myelines (less soluble in 

 ether), and lecithins (characterised by their extreme instability). In 

 each of these ill-defined groups several members with their empirical 

 formulas are described. Thudichum's work has been so far confirmed 

 by that of Kossel, in that he has shown that protagon is not a single 

 substance, but that there is more than one protagon. They yield either 

 one or two or perhaps three derivatives (cerebrosides), called cere- 

 brin, kerasin or honiocerebrin, and encephalin ; and, further, probably 

 several lecithins are obtainable from the different protagons. The 

 constitution of lecithin is discussed on p. 22, and there it will be seen 

 that the existence of several lecithins (i.e. containing different fatty acid 

 radicles) is mooted. The protagons, according to Kossel, resemble each 

 other in the following points : 



1. They contain carbon, hydrogen, nitrogen, oxygen, and phosphorus. 

 Elementary analysis gives practically the same results as those obtained 

 by other observers. But the existence of sulphur in some varieties of 

 protagon is a new point. 



2. By oxidation with nitric acid they yield higher fatty acids (palmitic 

 and stearic). 



8. By the action of boiling sulphuric or hydrochloric acid a reducing 

 carbohydrate is formed. 



4. By the action of alkalis they yield cerebrosides (formerly called 

 cerebrins). 



5. The cerebrosides are the source of the reducing carbohydrate 

 mentioned above. 



6. The carbohydrate formed is galactose. 



7. Other decomposition products of the cerebrosides are ammonia, and 

 a complex material which on fusion with potash yields higher fatty acids. 



The cerebrins or cerebrosides. These substances, the glucoside 

 constitution of which lias just been alluded to, form a group of ill- 

 defined, nitrogenous substances, existing especially in the white sub- 

 stance of nervous tissue, and also in the yolk of egg, pus corpuscles, 

 and spleen cells. 2 



1 Rep. Med. Off. Privy Council, London, 1874, p. 



2 Hoppe-Scyler, "Ph'ysiol. Chem.," S. 720, 788. 



113 et seq. 



