470 VICTOR C. MYERS 



that the glycerophosphoric acid of cophalin is identical with that of lecithin. 

 It also appeal's to contain another unsaturated fatty acid, namely, 

 cephalinic acid, in place of oleic acid. The formula would thus be : 



H 2 C O - COC 17 H 31 



I 

 H C O COC 17 H 31 



I 

 H 2 C O P = O 



/\ 



HO O CH 2 .CH 2 .NH 2 



Two other monaminophosphatids found in brain tissue are paramyelin 

 and myelm, the latter being present only in very small amounts. Diamino- 

 monophosphatids are also present in brain tissue. Two have been 

 recognized, amidomyelin and sphingomyelin. In the case of this latter 

 compound Thudichum recognized that it did not contain glycerol. Levene 

 has recently obtained on hydrolyzing sphingomyelin, phosphoric acid, two 

 fatty acids, cerebronic and lingoceric, and three basic substances, cholin, 

 sphingosin and a base of the composition C 17 H 35 NO. 



Cerebrosids. The cerebrosids are nitrogenous substances free from 

 phosphorus, which yield galactose on boiling with dilute mineral acids. 

 They also contain a complex fatty acid. As would seem evident from 

 the table above they are not found in the embryonic brain, but develop as 

 medullation comes on and are found chiefly in the medullary sheaths in 

 the white matter of the brain. The most important of the cerebrosids 

 are phrenosin and cerasin. On hydrolysis phrenosin apparently yields 

 cerebronic acid, galactose and sphingosin, while cerasin yields ligno- 

 ceric acid, galactose and sphingosin. Thus the important difference in 

 the two substances appears to be in the fatty acid they contain. Phrenosin 

 has been somewhat more studied than cerasin. 



Sulphatids. It has been suggested by Koch that the oxidized sulphur 

 always present in cerebrosids when impure has a union in the form of 

 sulphuric acid with a cerebrosid and a phosphatid as follows: 



O 



Cerebrosid O S O Phosphatid 



II 

 O 



Its nature is unknown. 



Thudichum has also isolated in small amounts two amino-lipotids, 

 crinosin and bregenin. 



Cholesterol. Cholesterol is the chief sterol present in brain. Choles- 

 terol melts at 145. There is another sterol present which melts at 137, 



