384 V. BLOOD LIPIDS 



same proportionate difference in phospholipid distribution between the 

 plasma and the cells has been observed in children. 197 Moreover, a 

 different composition of the phospholipid fraction obtains in the plasma and 

 in the cells. Williams, Erickson, et al. 198 reported that cephalin makes up 

 50 to 60% of the total phospholipid in the cells, while it comprises less than 

 10% in the plasma. 50 ~ 52 Using a new micromethod for the determination 

 of individual phospholipids, Erickson et aZ. 62 later confirmed the earlier 

 results, and showed the following absolute and percentage distribution of 

 phospholipids in human erythrocytes per 100 g. : total phospholipid, 317 

 mg.; total choline phospholipids, 127 mg., 40%; lecithin, 77 mg., 24%; 

 cephalin, 190 mg., 60%; and sphingomyelin, 50 mg., 16%. Using the 

 same microprocedure, these workers reported the following figures per 100 

 ml. in human plasma: total phospholipid, 189 mg.; total choline phos- 

 pholipids, 134 mg., 71%; lecithin, 99 mg., 52%; cephalin, 55 mg., 29%; 

 and sphingomyelin, 35 mg., 19%. 



Cholesterol makes up 125 to 150 milligram per cent per 100 ml. of cells, 

 in normal human subjects, but no appreciable amount of the cholesterol is 

 present in the ester form. 199 Although this quantity is somewhat less 

 than that in the plasma, the concentration per 100 ml. of water is approxi- 

 mately the same in the two fractions. Erickson and co-workers 197 reported 

 that the cholesterol in the red blood cells of children averaged 129 milli- 

 gram per cent, as much as 32% being in ester combination. In adults 

 esterified cholesterol was found to make up 16% of the total blood chole- 

 sterol. The comparative levels of cholesterol and phospholipid in the plasma 

 and cells of forty normal adults are summarized in Table 7. The averages 

 include those for twenty young healthy adults and twenty old patients with 

 no known disorder in lipid metabolism. Since practically no differences 

 obtained in the lipid values of the two age groups, Foldes and Murphy 200 

 reported the results of the combined groups as comprising the normal mean 

 values. 



Hagerman and Gould, 201 employing plasma and cells containing C 14 - 

 labeled cholesterol obtained by feeding C 14 -acetate, showed that free chole- 



197 B. N. Erickson, H. H. Williams, F. C. Hummel, and I. G. Macy, J. Biol. Chem., 

 118, 15-35(1937). 



193 H. H. Williams, B. N. Erickson, I. Avrin, S. S. Bernstein, and I. G. Macy, J. Biol. 

 Chem., 123, 111-118(1938). 



199 G. C. Brun, Cholesterol Content of the Red Cells in Man, H. K. Lewis, London, 1939; 

 Acta med. Scand., Suppl. 99, 1-237 (1938). 



200 p y. Foldes and A. J. Murphy, Proc. Soc. Exptl. Biol. Med., 62, 215-218, 218-223 

 (1946). 



201 J. S. Hagerman and R. G. Gould, Proc. Soc. Exptl. Biol. Med., 78, 329-332 (1951). 



