248 ANIMAL FATS AND PHOSPHATIDES. 



the above, or the solid lecithin is boiled one hour with baryta-water, 

 filtered, and the excess of baryta precipitated by CC>2; filter while hot, 

 concentrate to a syrup, and extract with absolute alcohol, when the 

 insoluble barium glycerophosphate remains; then precipitate the filtrate 

 with an alcoholic platinum chloride solution. 



H 2 .OH 



Glycerophosphoric acid, C 3 H 9 P0 6 =CH.OH , is a bibasic acid which prob- 



CH 2 0\ 

 OH-)PO 

 OH/ 



ably occurs in the animal fluids and tissues only as a cleavage product of lecithins. 

 According to WILLSTATTER and LUDECKE x the glycerophosphoric acid split off 

 from lecithins is optically active. Its barium and potassium salts are levorotatory, 

 and behave in certain respects differently from the corresponding salts of syn- 

 thetically prepared glycerophosphoric acid. The Ba and Ca salts of glycero- 

 phosphoric acid are crystalline and are more soluble in cold than in warm water. 

 The acid itself is a syrupy fluid. 



Cephalin is also a monoaminophosphatide whose formula, based upon 

 the investigations of THUDICHUM, KOCH, THIERFELDER and STERNA is 

 probably C42Hs2NPOi3. The views of these investigators as to the con- 

 stitution of this body, which is difficult to purify, differ very considerably. 

 According to THUDICHUM, on cleavage it yields neurine, glycerophosphoric 

 acid, stearic acid, and a specific fatty acid, cephalic add. According to 

 KOCH it contains, on the contrary, only one methyl group attached to 

 nitrogen, and is therefore probably dioxystearylmonomethyl lecithin. 

 FRANKEL and DIMITZ found no choline, while according to COUSIN it 

 yields, like lecithin, stearic acid, an unsaturated fatty acid, glycero- 

 phosphoric acid and choline as decomposition products. The glycero- 

 phosphoric acid from brain cephalin gives, according to FRANKEL and 

 DIMITZ, a dextrorotatory Ba salt and is therefore not identical with the 

 glycerophosphoric acid from lecithin. According to these investigators 

 the cephalin of the human brain is a mixture of palmityl and stearyl- 

 cephalin. Besides these two fatty acids cephalin also contains an unsat- 

 urated fatty acid, cephalinic add, which according to PARNAS S is related 

 to leinoleic acid or perhaps identical therewith. 



From the investigations carried on thus far we can conclude that 

 cephalin differs from lecithin in that it contains cephalinic acid, another 

 glycerophosphoric acid and probably no choline but a monomethyl 

 base. Cephalin has probably never been obtained in a pure form. 



1 Ber d. d. chem. Gesellsch., 37. 



* Thudichum, 1. c.; Koch, Zeitschr. f. physiol. Chem., 36; Thierf elder and Stern, 

 ibid. 53. 



3 Frankel and Dimitz, Bioch. Zeitschr., 21; Parnas, ibid., 22; Cousin, Compt. 

 Rend. soc. biol., 62. 



