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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 CO2; 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.
CH2.OH
Glycerophosphoric acid, C3H9P06 =CH.OH , is a bibasic acid which prob-
CH2
—0\
OH->PO
OH/
abfy occurs in the animal fluids and tissues only as a cleavage product of lecithins.
According to Willstatter and Ludecke 1
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 Stern,2 is
probably C42H82NPO13. 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 acid. 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 acid, which according to Parnas 3 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; Thierfelder and Stern,
ibid. 53.
3
Frankel and Dimitz, Bioch. Zeitschr., 21; Parnas, ibid., 22; Cousin, Compt.
Rend. soc. biol., 62.
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