608 BRAIN AND NERVES. 



ordinary temperature, and that as shown by ROSENHEIM and TEBB, 

 on dissolving in pyridine at 30 C. and heating or cooling the solution 

 deposits a precipitate of a substance rich in phosphorus. Although we 

 generally consider the phosphorized component of protagon as lecithin, 

 still, according to ROSENHEIM and TEBB, it is probably a diamido- 

 phosphatide, called sphingomyelin by THUDICHUM. On boiling protagon 

 with dilute mineral acids it yields galactose, due to the decomposition 

 of the cerebrosides. 



Protagon appears, when dry, as a loose white powder. It dissolves 

 in alcohol of 85 vols. per cent at 45 C., but separates on cooling as a 

 snow-white, flaky precipitate, consisting of globules or groups of fine 

 crystalline needles. On heating to 150 it becomes yellowish, softens 

 at 180 and melts sharply at 200 forming a brown, oily liquid (CRAMER). 

 It is difficultly soluble in cold alcohol or ether, but dissolves, at least 

 when freshly precipitated, in ether on warming. It dissolves in methyl 

 alcohol containing chloroform and, as above stated, separates cerebron. 

 Protagon is soluble in pyridine at 30 C., yielding a clear solution, and 

 this solution has a specific rotation ()D == +6.9 to 7.7 according to 

 the concentration of the solution (WILSON and CRAMER). On warm- 

 ing or cooling according to ROSENHEIM and TEBB, the rotation changes 

 with the separation of sphingomyelin so that it first diminishes in rota- 

 tion, then is zero, and then becomes strongly levorotatory until it reaches 

 242, and finally, when nearly all the sphingomyelin has separated 

 out it becomes constant at about 13.3. The strong levorotation 

 depends upon the accumulations of doubly refracting spheroid crystals 

 of sphingomyelin. With little water protagon swells up and is partly 

 decomposed. With more water it forms a jelly or pasty-like mass which, 

 with the addition of considerable water, forms an opalescent liquid. 



Protagon can be prepared in the following way: The finely ground 

 brain-mass, as free as possible from blood and membrane, is dehydrated, 

 which is best done by cold acetone or by grinding with burned plaster-of- 

 paris or anhydrous sodium sulphate, and then extracted with ether. 

 The mass is then extracted at 45 C. with 85 vol. per cent alcohol until 

 the filtrate when cooled to C. gives no more precipitate. All the 

 precipitates obtained on cooling to C. are extracted with ether and 

 recrystallized from alcohol. Further details can be found in the cited 

 works of CRAMER, WILSON, GIES, ROSENHEIM and TEBB. 



Among the phosphatides occurring in the brain we must mention besides the 

 lecithin and cephalin, the following substances. 



Myelin, C^H^NPOio, according to THUDICHUM, is not well'known but is char- 

 acterized by the fact that its alcoholic solution is not precipitated by CdCl 2 or 

 PtCl 4 . On the contrary an alcoholic solution of lead acetate gives a precipitate. 

 The existence of a second monaminomonophosphatide, paramyelin, C 3 8 

 according to THUDICHUM, is very improbable. 



