THE METABOLISM OF FAT 437 



fat plugging the small bloodvessels, as would be the case if it were 

 in a state of fine emulsion. It is also better available for storage in 

 the various fat depots of the body. 



The fat depots of the body are situated in the subcutaneous tissue, 

 in the subperitoneal tissue, between the muscles, and around various 

 organs of the body, such as the kidney and the eyeball. The depots of 

 fat act primarily as the storehouses of a food possessed of great energy 

 value. They also protect the body from heat loss, and act as cushions, 

 giving form and beauty to the body, preventing jarring, and giving 

 support to the various organs. The haggard face, the chilly tempera- 

 ment, and the falling down of the viscera, alike result from want of 

 fat. Fat is also stored intracellularly in other cells -e.g., muscle 

 fibres and the liver cells beside those of the true adipose tissue, 

 much of it in a masked form, probably combined with protein or 

 other bodies, so that it does not react with fat stains. 



The fat in the various depots is not always of the same character. 

 It is more fluid in some parts than others. Cheniically, also, the 

 same difference is found. 



This is shown in the following table : 



The fats of the subcutaneous tissue are chiefly compounds of 

 oleic, stearic, and palmitic acids. From the fats of the liver, kidney, 

 heart muscle, however, acids are found more unsaturated than oleic. 

 belonging to the linoleic and linolenic series. 



The fat of milk is also characterized by the presence, in addition 

 to the ordinary fats, of butyric and other volatile fatty acids. The 

 lower melting-point of the fat of the pig's back may allow mobility 

 of the tissues there, exposed as they are to the cool atmosphere. The 

 melting-point may be adapted to keep the fat of any part soft, but 

 not fluid. The melting-point of the subcutaneous fat is altered by 

 covering the pig 's back with a sheep's pelt. The fat stored within the 

 body may arise from three sources: (1) Ingested fat, (2) carbohydrate r 

 (3) proteins. 



Fat from Fat.^-That fat arises from ingested fat is easily capable 

 of demonstration. Nature makes experiment for us. It can be 

 shown that the fat of the sea-dolphin has a high iodine value when 

 the fish it feeds on have fats of a high iodine value. When the fish 

 eaten have fats of a low iodine value, the iodine value of the fat of 

 the dolphin falls. The fat of the fish-eating ducks has a high iodine 

 value (84-8), that of farm duck a lower value (58-5). Horses fed on 

 oats have an oily fat of a high iodine number similar to that of the 



