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 l 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 w.ere 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 wdth 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 HENRIQTJES 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. 

 CH 2 ON 



HO-^PO 



X C 2 H 4 -(X o 



Nf(CH 3 )3 

 N 



1 Zeitschr. f. physiol. Chem., 51. 



2 Strecker, Annal. d. Chem. u. Pharm., 148; Hundeshagen, Journ. f. prakt. Chem. 

 (N. F.), 28; Gilson, Zeitschr. f. physiol. Chem., 12. A different view is held by 

 Malengreau and Pridgent, ibid., 77. 



1 Thudichum, Die chemische Konstitution des Gehirns des Menschen, etc., Tubingen, 

 1901. 



4 Henriques and Hansen, Skand. Arch. f. Physiol., 14 (1903); Cousin, Compt. 

 Rend., 137; Erlandsen, Zeitschr. f. physiol. Chem., 51. 



