THE LECITHINS 425 



on liver lecithin, Levene and Simms^^" found palmitic and stearic acids, 

 and two unsaturated fatty acids, one of which could be transformed by 

 hydrogenation to stearic acid, while the second one (probably arachidonic 

 acid), on similar treatment, yielded arachidic acid. On another occasion, 

 Levene and Simms^^^ reported the isolation of oleic and arachidonic acids 

 from the sample. Brominated liver lecithin yielded palmitic, stearic, 

 and octobromarachidic acid, which may have differed from the other 

 preparation of Levene and Simms.'^" Further proof of differences in 

 composition may be gleaned from the fact that the purified cadmium 

 chloride compounds of liver lecithin are more highly unsaturated than are 

 those of egg-yolk lecithin; (his is indicated by the fact that the iodine 

 number varied between 59 and 84 in the former case as contrasted ■with 30 

 to 54 in the later products. ^^''' 



There is no reason to question the authenticity of the various fatty acid 

 combinations which ha\ e been isolated from the different lecithin prepara- 

 tions obtained from the same natural sources. It is possible that wide 

 varieties of fatty acids may exist in any single preparation, while only 

 certain lecithins would be separated by the specific methods employed in 

 purification. According to vSinclair,^^^ it is more probable that variations 

 in the fatty acid makeup of animal lecithins do occur from time to time, 

 depending upon the nature of the diet. Thus, the appearance of clupano- 

 donic acid in the egg lecithin from Japan might readily be traced to the 

 presence of fish oils in the diet of the hens. 



The general opinion seems to be prevalent that the lecithin molecule 

 contains equal proportions of saturated and of unsaturated fatt}' acids. '*'^* 

 There has been no confirmation of the reported isolation of an egg-yolk 

 lecithin containing only stearic acid^^ or of another preparation from a 

 similar source composed only of two oleic acid molecules. ^"-^^^ Bloor^^*~^'^ 

 prepared the lecithin fractions of numerous phospholipids from heart and 

 other muscles, liver, kidney, pancreas, and lung. When these were further 

 fractionated into the liquid and solid fatty acids, it was found that both 

 t3"pes of acids were in^'ariably present. However, the later work of 

 gjQQj.136 g^j^f^j q£ Sinclair^^' leaves the 1 : 1 ratio of saturated to unsaturated 

 acids open to question, since the proportion of saturated fatty acids was too 

 low (25-30%), although the unsaturated (liquid) acids were found to be 

 present in about the theoretical amount (50%). However, Thierfelder 



130 p. A. Leveue and II. S. SiiniiKs ./. Biol. Chent., 48, 185-190 (1921). 

 "1 P. A. Levene and H. 8. Simms, J. Biol. Chem., 51, 285-294 (1922). 

 1" R. G. Sinclair, J. Biol Chem., 86, 579-586 (1930). 



133 p. Bergell, Ber., S3, 2584-2586 (1900). 



134 W. R. Bloor, J. Biol. Chem., 68, 3.3-56 (1926). 

 13* W. R. Bloor, J. Biol. Chem., 72, 327-343 (1927). 



136 W. R. Bloor, J. Bix)l. Chem., 80, 443-454 (1928). 



137 R. G. Sinclair, /. Biol. Chem., 97, xxxiv-xxxv (1932). 



