HEAT AND LIFE. 135 



musculin, ossein, pepsin, pancreatin, compounds all differ- 

 ing very slightly. It is the first portion of the chemical 

 process which is effected in the principal fluid of the body. 

 All these materials, elaborated at different points of the 

 circulating current, and designed to be assimilated, are de- 

 stroyed in the very organs in which they had been fixed. 

 The glycogene is transformed into sugar, which is burned, 

 yielding water and carbonic acid ; the fatty acids are partly 

 eliminated by the skin, and partly burned. As to the plas- 

 tic matters which form the web of the tissues, we know lit- 

 tle about the chemical relation which connects these with 

 their products of destruction urea, creatine, cholesterine, 

 uric acid, and xanthine. Such is a rapid sketch of the prin- 

 cipal chemical phenomena which, taking place throughout 

 the entire system, kindle everywhere an evolution of more 

 or less intense heat. There is no central organ, then, for 

 feeding the vital fire every anatomical element performs 

 its share ; and, if a nearly uniform temperature exists 

 throughout the body, it is because the blood diffuses heat 

 regularly into the various parts it bathes. 



Now, how can the amount of heat to which these reac- 

 tions may give rise be ascertained ? Lavoisier arrived at 

 it in a very simple manner. After comparing the oxygen 

 absorbed by the animal with the carbonic acid and watery 

 vapor thrown off, he deduced the weight of the carbon and 

 hydrogen burned, by assuming that the formation of car- 

 bonic acid and of water produces in the system the same 

 amount of heat that it would produce if taking place by 

 means of free carbon and hydrogen. This is very nearly 

 the result he obtained : A man weighing 132 pounds burns 

 in 24 hours, at the average temperature of Paris, very near- 

 ly 11 ounces of carbon, and -^J of an ounce of hydrogen, 

 and thus develops 3,297 heat-units. During the same 

 period he loses through his lungs and skin 2f pounds of 

 watery vapor, which take from him 697 heat->units, There 



