396 V. BLOOD LIPIDS 



pathological conditions as diabetes mellitus, and in diseases of the thyroid 

 gland. These several factors will be summarized first for the blood com- 

 ponents in which a close interrelation exists (neutral fat, phospholipid, 

 cholesterol) and then for each of the other components separately. 



(1) Factors Altering the Concentration of Neutral Fat, 

 Phospholipids, and Cholesterol • 



Since the levels of the three main lipids in the blood, namely, neutral 

 fat, phospholipids, and cholesterol, are interrelated, it seems best to con- 

 sider them together. The concentration of phospholipids and of cholesterol 

 in the blood is related to that of neutral fat; when fats are ingested, there 

 is a marked rise of the neutral fat level in the blood, together with con- 

 comitant changes in the phospholipid and cholesterol fractions. The inges- 

 tion of phospholipid affects the concentration of neutral fat and cholesterol. 



a. The Effect of Age. (a) Total Blood Lipids in the Newborn and in 

 Young Children. Although the fatty acids are able to pass into the fetus, 

 the composition of the blood lipids in the newborn substantiates the fact 

 that the maternal-fetal transfer does not bring about an equilibrium in 

 the composition of the blood of mother and child. There is considerable 

 evidence that not only fatty acids, but also phosphatides and cholesterol, 

 are lower in infancy than in the adult. I97 - 238,239 Boyd 238 found that the total 

 plasma lipid in newborn infants amounted to only 198 ± 80 milligram per 

 cent and 3.3 ± 1.9 meq. of neutral fat-fatty acids per 100 ml. 202 Gyorgy, 240 

 Plass and Tompkins, 241 and Hellmuth 242 have all reported low values for 

 the blood lipids of the newborn as contrasted with those of the mother. 

 Total lipids in children three to eleven years old approximate the levels in 

 adults. 243 Newborn rats also have a low blood lipid level. 244 



(6) Blood Phospholipids in the Newborn and in Young Children. Accord- 

 ing to Boyd, 238 the lipid phosphorus of the newborn is at the low level of 

 2.5 ±1.3 milligram per cent. Gyorgy 240 reported that the phospholipid 

 level rises more rapidly than does that of cholesterol during the first two 

 weeks following birth, after which cholesterol increases more rapidly. 

 For comparative levels of phospholipid and cholesterol, see Table 9. 



238 E. M. Boyd, Am. J. Diseases Children, 52, 1319-1324 (1936). 



239 A. D. Kaiser and M. S. Gray, Am. J. Diseases Children, 47, 9-24 (1934). 



240 P. Gyorgy, Jahrb. Kinderheilk., 112, 283-297 (1926). 



241 E. D. Plass and E. H. Tompkins, J. Biol. Chem., 56, 309-317 (1923). 



242 K. Hellmuth, Arch. Gyn&kol, 127, 293-361 (1926). 



243 D. M. Cowie and L. A. Hoag, /. Am. Med. Assoc, 77, 1493-1494 (1921). 



244 A. Mayer and G. Schaeffer, Compt. rend., 159, 102-105 (1914). 



