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242 ANIMAL FATS AND PHOSPHATIDES.
preparation. They are generally all precipitated from their solution
by acetone although not completely, and this behavior is also of especial
importance in their preparation. The phosphatides are also nearly all
precipitated by metallic salts, especially by platinum chloride and cad-
mium chloride, and this method is also often used in their preparation.
The usefulness of this method has been questioned at least for certain
phosphatides, since Erlandsen * showed that a decomposition occurs.
Erlandsen has also found that when finely divided heart-muscle, dried in
the air, is completely extracted with ether and then with alcohol, the first extract
contains the monophosphatides, and the alcohol extract contains the diamino
phosphatides which were not free in the tissues, but existed in the combined state.
Whether this observation is of general importance in the preparation of pure
phosphatides remains to be seen.
As the phosphatides among themselves are rather difficult to char-
acterize and as there is a question whether a pure phosphatide has thus far
been prepared it seems of little interest to give a review here of the division
of the isolated phosphatides among the different groups. In this chapter
we will only discuss the three most studied phosphatides, namely, lecithin,
cephalin and cuorin; the others will be treated of in the respective chapters.
Lecithins. In correspondence with the generally accepted view
lecithin is a monoaminomonophosphatide, which’ forms an ester com-
pound of glycerophosphoric acid substituted by two fatty-acid radicals
with a base called choline,2
hence there must exist several groups of
lecithins. According to the kind of fatty acid contained in the lecithin
molecule it is possible to have various lecithins, such as stearyl-, palmityl-,
and oleyl-lecithins. According to Thudichum 3 every true lecithin always
contains at least one oleic-acid radical. According to the investigations
of Henriques and Hansen, Cousin and Erlandsen,4
there is no ques-
tion that the so-called lecithin of the egg-yolk and muscles must contain
a fatty acid, still less saturated than oleic acid. All lecithins are mon-
aminophosphatides, according to the following type:
CH2— —fatty-acid radical.
CH — —fatty-acid radical.
CH2—(X
hcApo
/C2H4—O/
N£-(CH8 ) 3
MDH
1
Zeitschr. f. physiol. Chem., 51.
2
Strecker, Annal. d. Chem. u. Pharm., 148; Hundeshagen, Journ. f. prakt. Chem.
X. V.), 28; Gilson, Zeitschr. f. physiol. Chem., 12. A different view is held by
Malengreau and Pridgent, ibid., 77.
* Thudichum, Die chemische ^Constitution des Gehirns des Menschen, etc., Tubingen,
IfiOl.
4
Henriques and Hansen, Skand. Arch. f. Physiol., 14 (1903); Cousin, Compt.
Piend., 137; Erlandsen, Zeitschr. f. physiol. Chem., 51.
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