358 V. BLOOD LIPIDS 



fatty acids, with oleic acid as the chief unsaturated acid. The more highly 

 unsaturated acids and the short-chain saturated acids are absent from the 

 neutral fat fraction. Red blood cells are practically devoid of neutral fat. 47 



(3) Phospholipids 



The phospholipids present in blood consist of all of the three main types, 

 namely, lecithins, cephalins, and sphingomyelins. The phospholipids are 

 higher in the red blood cells than in the plasma, and the distribution of 

 lecithin, cephalin, and sphingomyelin differs for these two fractions of blood. 



Artom 49 was the first to call attention to the fact that serine-containing 

 phospholipids occur in human plasma. However, it was recognized that 

 they represented only a minor fraction of the total phospholipids. Taurog, 

 Entenman, and Chaikoff 50 later showed that the phospholipids present in 

 the plasma of dog and man consist almost entirely of the choline-containing 

 phospholipids, lecithin and sphingomyelin. Only 5% of the total phos- 

 pholipid failed to contain choline, and therefore could be considered as 

 belonging to the cephalin fraction. Hack 51 confirmed the work of Taurog 

 et al., b0 insofar as human blood plasma is concerned, by demonstrating the 

 proportion of lecithin : cephalin : sphingomyelin as 78.8:5.2:16.0. More- 

 over, Sinclair 52 reported that cephalin makes up only 3 to 8% of the total 

 phospholipids of beef, dog, and pig serum, as well as of human serum. 



On the other hand, in the case of the fowl, cephalin apparently plays a 

 more important role in the blood than it does in other animals. Thus, 

 Flock and Bollman 53 found that only 53% of the phospholipid in the plasma 

 of the chicken consisted of the choline-containing fraction. Similar re- 

 sults were noted for the turkey (Meleagris gallipavo) by Sinclair, 52 who re- 

 ported that cephalin comprises 20% of the total plasma phospholipids in 

 this species. Using newer and more reliable methods for cephalin, 54,55 

 Ranney and associates 56 found that the plasma of the normal, immature 

 male fowl contains, on an average, 21% of cephalins, 65% of lecithins, 



49 C. Artom, J. Biol. Chem., 157, 595-599 (1945). 



60 A. Taurog, C. Entenman, and I. L. Chaikoff, /. Biol. Chem., 156, 385-391 (1944). 



51 M. H. Hack, /. Biol. Chem., 169, 137-143 (1947). 



62 R. G. Sinclair, J. Biol. Chem., 174, 343-353 (1948). 



63 E. V. Flock and J. L. Bollman, J. Biol. Chem., 144, 571-577 (1942). 



64 A. Taurog, C. Entenman, B. A. Fries, and I. L. Chaikoff, J. Biol. Chem., 155, 19-25 

 (1944). 



66 G. Schmidt, J. Benotti, B. Hershman, and S. J. Thannhauser, J". Biol. Chem., 166, 

 505-511 (1946). 



66 R. E. Ranney, C. Entenman, and I. L. Chaikoff, J". Biol. Chem., 180, 307-313 

 (1949). 



