THE PRODUCTION AND DISSIPATION OF HEAT 



1091 



evolved is the calorie, i.e., the quantity of heat which is necessary to 

 raise 1 kilogram of water 1 C. (from 15 to 16 C.). We also speak at 

 times of the small calorie which refers to the amount of heat which is 

 required to raise 1 gram of water 1 C. Supposing, therefore, that the 

 quantity of water in the calorimeter weighs 10 kilos and that the 

 temperature rises 1 C. every half -hour, then the amount of heat liber- 

 ated by the animal during this time amounts to 10 calories or to 480 

 calories in the course of a day. This calculation, however, can be 

 correct .only if the body-temperature of the animal has remained the 

 same during this period, and if the metal of the calorimeter has not 

 absorbed an undue amount of this heat. The latter factor cannot 

 possibly interfere with this determination if the instrument is well 



FIG. 528. SCHEMATIC OUTLINE OF THE RESPIRATION CALORIMETER. 

 A, Dead air space between copper and zinc walls; B, dead air space between zinc 

 wall and wooden wall; C, dead air space between inner and outer w.ooden walls. E, 

 tube for food; S and H, inlet and outlet for water; V, air circulation. ~~ (Atwater and 

 Benedict.) 



protected against heat-loss, and if the experiment is continued for a 

 relatively long period of time. 



More recently, Atwater has made use of calorimeters large enough 

 to accommodate human beings, so that the heat produced by them may 

 be brought into relation with their respiratory interchange. The 

 air within this chamber is kept at a constant temperature by a stream 

 of water passed through it in a series of tubes. If the temperature 

 of this water, as well as the volume of the through flow which is required 

 to accomplish this end, is then ascertained, it is possible to obtain 

 from these values the amount of heat liberated by the person. Besides, 

 air is drawn out of this chamber by an engine, its volume being reg- 

 istered by a gas-meter. From time to time samples of this air are 

 withdrawn for analysis which includes the determination of its carbon 



