192 PHYSIOLOGICAL CHEMISTRY 



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- 

 ment consists in observing any change in the temperature of the 

 patient or the apparatus. The sum of these three factors will 

 give the total heat given off by the subject. 



The circulating air is in a closed system. The carbon dioxide 

 is removed by passing the air through an absorption apparatus, 

 and its amount can be determined by weighing. Oxygen is sup- 

 plied from an oxygen retort, so that the amount used by the 

 subject can be determined accurately by the loss of weight of 

 the retort, considered in connection with any change in the 

 composition of the circulating air. 



By means of this calorimeter, accurate measurements may be 

 made of the heat produced in the body, and the amount of car- 



