HEAT AND LIFE. 135 
musculin, osséin, 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 pcunds burns 
in 24 hours, at the average temperature of Paris, very near- 
ly 11 ounces of carbon, and 44 of an ounce of hydrogen, 
and thus develops 3,297 heat-units. During the same 
period he loses through his lungs and skin 22 pounds of 
watery vapor, which take from him 69% heat-units, There 
