234 ANIMAL FATS AND PHOSPHATIDES. 



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 cadmium 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 diamido 

 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. 



In consideration of the uncertainty which exists as to the properties 

 and chemical individuality of the various phosphatides, we will here only 

 discuss in detail the most carefully studied phosphatides, namely, lecithin 

 and cuorin. The others will be discussed in their proper place. 



Lecithins. These bodies are ester compounds l of glycerophosphoric 

 acid substituted by two fatty-acid radicals with a base called choline. 

 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 TnuDicHUM 2 every true lecithin always 

 contains at least one oleic-acid radical. According to the investigations 

 of HENRIQUES and HANSEN, COUSIN and ERLANDSEN, S 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- 

 amidophosphatides, according to the following type: 



CH 2 O fatty-acid radical. 

 CH fatty-acid radical. 



CH 2 O\ 



HO-^EO 

 yC 2 H 4 O/ 

 Nf(CH 3 ) 3 

 \OH 



The various lecithins stand close to each other in regard to constitu- 

 tion. The amount of phosphorus varies between 3.7-3.97 per cent and 

 the amount of nitrogen between 1.7-1.9 per cent. The so-called di- 



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

 (N. F.), 28; Gilson, Zeitschr. f . physiol. Chem., 12. 



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

 1901. 



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

 rend., 137; Erlandsen, Zetischr. f. physiol. Chem., 51. 



