METABOLISM 215 



a subsequent mouse or candle. He decided that the burning of 

 the candle consisted in a combining of the carbon of the candle 

 with a substance in the air which he called "oxygen," and that 

 in animals a similar process took place, producing the heat of 

 the body. By measuring the amount of ice melted in a given 

 time by the heat from an animal, and comparing the result with 

 the amount of carbon dioxide produced by the animal in a period 

 of similar length, he obtained results which indicated that at 

 least 96% of the heat produced by the animal could be accounted 

 for by the oxidation of carbon to C0 2 . He further showed that 

 oxygen also was used up in combining with hydrogen to form 

 water. He also arrived at the result that more heat was pro- 

 duced when the animal was subjected to cold than otherwise, 

 and that digestion and work increased the heat output. Un- 

 fortunately, Lavoisier lost his life on the guillotine during the 

 Reign of Terror, and his brilliant work was left unfinished. 



The way had been opened, however, and other workers took 

 up the problems which the brilliant Lavoisier had opened. The 

 methods and ideas of Lavoisier were extended and im- 

 proved. Dulong and Depretz, Regnault and Reiset, Rubner and 

 others abroad, and Atwater, Benedict, Lusk, du Bois and others 

 in this country have investigated and solved many of the prob- 

 lems connected with energy balance and energy requirements. 

 The work of Atwater in this country has been of particular 

 service from the point of technique development. Atwater, in 

 conjunction with Rosa constructed an apparatus known as a 

 calorimeter. This contrivance consists of an insulated chamber 

 large enough for a man. The walls are so constructed that no 

 heat is lost through them. The heat produced by the occupant 

 is carried off by water circulating through a cooling coil. The 

 flow of water and its temperature at entering and leaving the 

 chamber can be accurately measured, and thus the amount of 

 heat carried off from the chamber computed. A circulation of 

 air is provided, and from this, the moisture evaporated from the 

 subject is extracted and measured, and the heat consumed in 

 its vaporization calculated. A third factor in the heat measure- 



