LIPID CONTENT AND COMPOSITION OF ANIMAL 



577 



the dry, neutral fat-free basis was 8.62% (control, twenty-two days), 

 7.13% (adequate diet), 7.19 (high-fat diet), and 5.51% (high-carbohydrate 

 diet). In confirmation of the above results, Dvorak 260 reported that total 

 lipids (especially grycerides) increase most rapidly in very young rats (be- 

 fore eyes are open), while dry matter increases more rapidly in somewhat 

 older rats (after eyes are open) . He believes that this variation is related to 

 the state of development of the hypophysis. 



In another report of Williams et al. 261 in which the lipid concentration of 

 the several individual organs in rats was correlated with increasing age, it 



DAYS 



Fig. 2. Liver lipids of the chick from the day of hatching (Day H) to 36 days 

 of age: (■) total fatty acids; (#) esterified cholesterol; (C) free cholesterol; 

 (A) phospholipids. The values are expressed in per cent of the wet weight of the 

 tissue. Each point represents the average values obtained in 2 to 5 pools, each 

 of which contained 2 to 4 livers. More pools were taken from younger than 

 from older chicks. 262 



was shown that the fundamental change, common to all tissues, was the in- 

 crease in cephalin content. An increase in cerebrosides occurred in testes 

 and skeletal muscle, while a decrease in this component obtained in cardiac 

 muscle. There was an increased amount of sphingomyelin in kidney, lung, 



260 Z. Dvorak, Nature, 171, 432-433 (1953). 



261 H. H. Williams, H. Galbraith, M. Kaucher, E. Z. Moyer, A. J. Richards, and I. G. 

 Macy, /. Biol. Chem., 161, 475-484 (1945). 



262 C. Entenman, F. W. Lorenz, and I. L. Chaikoff, J. Biol. Chem., 133, 231-241 

 (1940). 



