USES OF THE FAT. 225 



show a fatty liver after a few hours. A short time after the 

 hepatic cells exhibit this repletion with fat, a similar condition 

 is found in the course of the biliary ducts, while both in them 

 and the gall-bladder the epithelium presents the same appear- 

 ances which are witnessed in the intestinal epithelium during 

 the absorption of fat. The fat, as it would seem, is secreted 

 from the blood into the hepatic cells, passes thence with the 

 bile into the biliary ducts, and from the biliary ducts is re- 

 absorbed into the blood. 



Another type of the production of fat is found in the 

 secretion of the milk, of the sebaceous matter of the skin, and 

 the cerumen of the ears. The characteristic difference here 

 is, that the cells are thrown off with the fat, and so being lost 

 to the body are continually replaced by new cells. That the 

 secretion of milk and that of sebaceous matter in the skin 

 should be analogous to each other is nothing surprising, if 

 what is now affirmed be admitted namely, that the mammary 

 gland is but an enormously developed and peculiarly formed 

 accumulation of cutaneous sebaceous glands, both being pro- 

 duced by a progressive proliferation from the internal layers of 

 the epidermis. Of the same description are the ceruminous 

 glands of the ear and the large glands of the armpit. 



Besides serving the mere mechanical purpose of a light, 

 soft, and elastic packing, filling the vacuities of the body, 

 affording support, facilitating motion, and protecting from the 

 injurious effects of pressure, the fat, being a bad conductor of 

 heat, serves as a means of retaining the warmth of the body, 

 especially in warm-blooded animals exposed to great natural 

 cold for example, in the whale tribe. 



But the subserviency of fat to the function of nutrition is 

 its most important use. It is ready at all times to maintain 

 the temperature of the body by supplying material for erema- 

 causis in the lungs. Thence, when the digestive process intro- 



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