602 



ANIMAL HEAT 



[CH. XL. 



chambers are filled with perfectly dry air before the experiment is 

 commenced. Leading from each air-space is a tube ; the two tubes 



FIG. 444. Air Calorimeter of Haldane, Hale White, and Washbourn. C, cage for animal. In order to 

 make the conditions in both chambers as much alike as possible, an empty cage should be placed in 

 the other chamber. 



are connected to the two limbs of a manometer (M) shaped as in the 

 figure, and containing oil of erigeron. 



The action of the calorimeter is as follows : In one chamber the 

 animal, the heat production of which is to be ascertained, is placed 

 within the cage C. In the other, hydrogen is burnt (H). Both 

 chambers are shut, the tubes AA, A'A' being clamped. The heat 

 given off from the animal warms its chamber, and thus increases the 

 pressure of the air in the air-space between the two copper walls of 

 the chamber. This would lead to movement of the fluid in the 

 manometer, but that the heat given off by the burning of the hydrogen 

 increases at the same time the pressure in the air-space between the 

 walls of its chamber. Tnis latter increase of pressure tends to make 

 the fluid in the manometer move in the other direction. If the fluid 

 in the manometer remains stationary, the amount of heat given off 

 by the animal is equal to that produced by the burning hydrogen ; 

 and during an experiment the fluid in the manometer is kept station- 

 ary by turning the hydrogen flame up and down. The amount of 

 hydrogen burnt is estimated by the amount of water formed, and the 

 heat of combustion of hydrogen being known, it is perfectly easy to 

 calculate the calories produced, which equal those given off by the 

 animal. 



The applicability of the law of the conservation of energy to diverse chemical 

 reactions has been amply demonstrated. In view of the chemical nature of meta- 

 bolism, we might assume that the same law applies to the reactions taking place in 

 the body, that it is in fact one of the fundamental laws of the universe. We have, 

 however, no scientific right to assume in advance that no special laws are operative 

 in living matter. The law therefore here requires experimental verification, and 

 much labour has accordingly been devoted to this problem. The early work of 

 Lavoisier, Crawford, Dulong, and others showed great discrepancies between the 

 heat actually found and that calculated, but with the advance of knowledge and 

 improvements of chemical methods and calorimetry, these have disappeared. It is 



