82 ORIGIN OF FAT IN 



of food, we check the processes of cooling and ex- 

 halation, as we do when we feed them in stables, 

 where free motion is impossible. 



The stall-fed animal eats, and reposes merely for 

 digestion. It devours in the shape of nitrogenised 

 compounds far more food than is required for repro- 

 duction, or the supply of waste alone ; and at the 

 same time it eats far more of substances devoid of 

 nitrogen than is necessary merely to support res- 

 piration and to keep up animal heat. Want of 

 exercise and diminished cooling are equivalent to a 

 deficient supply of oxygen ; for when these circum- 

 stances occur, the animal absorbs much less oxygen 

 than is required to con vert .into carbonic acid the 

 carbon of the substances destined for respiration. 

 Only a small part of the excess of carbon thus occa- 

 sioned is expelled from the body in the horse and 

 ox, in the form of hippuric acid ; and all the remain- 

 der is employed in the production of a substance 

 which, in the normal state, only occurs in small 

 quantity as a constituent of the nerves and brain. 

 This substance is fat. 



In the normal condition, as to exercise and labour, 

 the urine of the horse and ox contains benzoic acid 

 (with 14 equivalents of carbon); but as soon as the 

 animal is kept quiet in the stable, the urine contains 

 hippuric acid (with 18 equivalents of carbon). 



The flesh of wild animals is devoid of fat ; while 

 that of stall-fed animals is covered with that sub- 

 stance. When the fattened animal is allowed to 



