568 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



aliquot of the macerated, dried tissues. 249 In spite of the fact that consid- 

 erable variations in the composition of the lipids obtain in the various tis- 

 sues, the values noted for the mixed animal fats are characteristic of the 

 different species. 



The animal fats differ from the vegetable fats in containing a larger 

 variety of fatty acids. For a further discussion of the composition of ani- 

 mal and vegetable fats, the reader is referred to Hilditch, 116 and to Volume 

 I, pages 184-234. 



(4) The Distribution and Composition of the Lipids in the Storage Depots and 

 in the Several Organs 



a. The Normal Distribution of Lipids. Fat is stored in definite locations 

 in the animal; these differ somewhat in importance according to age and 

 sex, but not according to diet. These areas include (1) intermuscular, (2) 

 genital, (3) subcutaneous, (4) perirenal, (5) mesenteric, and (6) omental. 

 These have been exactly defined and described by Reed and co-workers. 250 



According to Reed et a/., 250 normal male rats weighing 250 g. after having 

 completed their period of most active growth were shown to have the follow- 

 ing distribution in per cent of total fat in the several fat depots : intermus- 

 cular, 9; genital, 13; subcutaneous, 55; perirenal, 16.4; mesenteric, 6.0; 

 and omental, 2.6. On the other hand, the comparative values for female 

 rats weighing 250 g., which were somewhat older than the male rats, were 

 as follows: intermuscular, 5; genital, 18; subcutaneous, 61; perirenal, 

 9.6; mesenteric, 5.0, and omental, 2.4. It would thus appear that male 

 rats have a higher proportion of storage fat in the intermuscular and peri- 

 renal depots, while the female has a larger proportion of subcutaneous and 

 genital fat. 



b. The Comparative Lipid Composition of Different Tissues. According 

 to Bloor, 251 those tissues and organs which have the greatest variety of 

 physiologic activities contain the highest concentration of lipids. In tis- 

 sues as, for instance, muscle, in which physiologic activity such as oxidation 

 is predominant, the cells contain ten to twenty times the concentration of 

 protein as of lipid. 252 On the other hand, in brain, liver, and other organs 



249 H. J. Deuel, Jr., L. F. Hallman, E. Movitt, F. H. Mattson, and E. Wu, /. Nutri- 

 tion, 27, 335-338 (1944). 



260 L. L. Reed, F. Yamaguchi, W. E. Anderson, and L. B. Mendel, J. Biol. Chem., 87, 

 147-174 (1930). 



251 W. R. Bloor, /. Biol. Chem., 132, 77-82 (1940). 



262 M. Kaucher, H. Galbraith, V. Button, and H. H. Williams, Arch. Biochem., 3, 203- 

 215 (1943). 



