NON-NITKOGKSTZED PRINCIPLES. 381 



sorption, fat may exist in certain quantity in the blood; 

 but it soon disappears, and is either destroyed directly in the 

 circulatory system, or is deposited in the form of adipose 

 tissue to supply a certain amount of this substance con- 

 sumed. That it may be destroyed directly is proven by the 

 consumption of fat in instances where the amount of adipose 

 matter is insignificant ; and that the adipose tissue of the 

 organism may be consumed is shown by its rapid disappear- 

 ance in starvation. 



The question of the relations of fat to nutrition is im- 

 portant, but somewhat obscure. It does not take part in the 

 nutrition of. the parts that are endowed, to an eminent de- 

 gree, with the so-called vital functions; and when these 

 tissues are brought to their highest point of functional de- 

 velopment, the fat is entirely removed from their substance. 

 If fat be not a plastic material, it would seem to have no func- 

 tion remaining but that of keeping up, by its oxidation, the 

 animal temperature. But it is not proven that fat, or fat and 

 sugar, are the sole principles concerned in the production of 

 carbonic acid and the generation of heat ; for both of these 

 phenomena occur in the carnivora, and in man, when fat and 

 sugar are eliminated from the food and the fat in the body has 

 been reduced to the minimum. Fat is undoubtedly destroyed 

 in the organism, and probably assists in the formation of the 

 carbonic acid eliminated; it is also taken in much larger 

 proportion in cold than in temperate or warm, climates; 1 

 but we cannot, with our present information, say without 

 reserve, that fats and sugar are oxidized directly, by a pro- 

 cess with which we are familiar under the name of com- 

 bustion, and that their exclusive function is the production 

 of animal heat. 



It is a curious fact that fat is generally deposited in tissues 

 during their retrograde processes. The muscular fibres of 

 the uterus, during the involution of this organ after partu- 

 rition, become the seat of a deposit of fatty granulations. 



1 See vol. ii., Alimentation, p. 128. 



