PHOSPHATIDES. 233 



yolk of the egg (STERN and THIERFELDER), and in muscles (ERLANDSEN), 

 and seem to be widely distributed. A triamidomonophosphatide, called 

 neottin by S. FRANKEL and BoLAFFio, 1 has been isolated from the yolk 

 of the egg, and according to THUDICHUM a tetramidomonophosphatide 

 occurs in ox bile. Among the monoamidodiphosphatides (P:N = 2:1) 

 we must mention cuorin, which was discovered and studied by ERLANDSEN, 

 and a phosphatide of the same type occurring in egg-yolk recently described 

 by MACLEAN. 2 According to THUDICHUM non-nitrogenous phosphatides 

 are also possible (in the brain) . If this be true these bodies must not, 

 for the present at least, be classified as phosphatides. 



The phosphatides seem to be closely related to each other; they 

 influence the solubility and precipitation properties of each other, and 

 are generally precipitated as mixtures which are extremely difficult 

 to separate into individual constituents. They are also amorphous, 

 and readily oxidized, and it is easy to understand why their preparation 

 in a pure state is so extremely difficult. Under these circumstances 

 we have no sufficient guarantee as to their chemical individuality, and 

 the descriptions of their properties and composition must be accepted 

 with a certain reservation. 



The phosphatides thus far investigated seem to be chiefly ester com- 

 binations between nitrogenous bases and fatty acid-glycerophosphoric 

 acid. According to THUDICHUM phosphatides exist which contain no 

 glycerin group. The fatty acids occurring in the phosphatides may be 

 of different kinds. It seems that at least one oleic acid radical, or another 

 still less saturated fatty acid, always occurs in the phosphatides. The 

 phosphatides on this account always take up iodine. They are, as above 

 stated, autooxidizable, taking up oxygen from the air and being readily 

 changed (ERLANDSEN) . They also give a beautiful reaction with PETTEN- 

 KOFER'S bile-acid test. The nitrogenous base is generally choline; in 

 certain cases their nature is not known, and in others the statements are 

 somewhat contradictory. 



The phosphatides are included in the group of lipoids, which are 

 difficult to characterize from a chemical standpoint, because they are 

 generally not soluble in water and because each phosphatide is dissolved by 

 at least one of the ordinary solvents of the fats. Among themselves they 

 may show quite a striking difference in behavior toward such solvents. 

 For example, one may be insoluble in cold alcohol or ether and another 

 soluble therein, and such differences are of importance in their prepara- 

 tion. They are generally all precipitated from their solution by acetone 



1 Hammarsten, Zeitschr. f. physiol. Chem., 36; Stern and Thierfelder, ibid., 53; 

 Erlandsen, ibid., 51; Frilnkel (and Bolaffio), Biochem. Zeitschr., 9. 



2 Thudichum, Virchow's Arch., 156; Erlandsen. 1. c.; MacLean, Zeitschr. f. physiol. 

 Chem., 57. 



