ANIMAL HEAT 



443 



)f the absolute amount of heat retained or lost by the animal above or 

 Delow the initial temperature, as well as that absorbed by the materials of 

 ;he apparatus in these various instances, the water equivalent of the tissues of 

 ;he animal and the materials of the calorimeter must be obtained, and then 

 idded to or subtracted from, as the case may be, the amount of water in the 

 :alorimeter , and the amount thus obtained multiplied by its rise in temperature. 



When means are taken to collect for purposes of analysis, the urine and 

 ;he feces and also the expired air, the apparatus is designated a respira- 

 ion calorimeter. The nitrogen in the urine and feces and the carbon dioxid 

 n the expired air permit of the determination of the amounts of protein 

 and fat metabolized. The ventilation of the chamber is accomplished by 

 some form of aspirating 

 apparatus. 



In properly conducted 

 experiments in which the 

 sources of error are reduced 

 to a minimum there is a 

 very close correspondence 

 between the total physio- 

 logic heat value of the food 

 and the amount collected 

 by the calorimeter. Thus, 

 in an experiment detailed 

 by Rubner, a dog was 

 given during twelve days 

 228.06 grams of protein and 

 340.4 grams of fat, the 

 physical heat value of which 

 was estimated at 4429 Cal- 



F IG . 203. WATER CALORIMETER or DULONG. D 

 and D'. Tubes for the entrance and exit of air. T and T'. 

 Thermometers for ascertaining the temperature of the 

 water. S. A mechanic contrivance for stirring the water 



im - for the purpose of distributing the absorbed heat uni- 



, Ti/forpc formly. To prevent the escape of heat with the expired 



The urine and feces *P gj tube g, is wound many times in the water-space 



beneath the animal cage. 



ones. 



during this period were col- 



determined, which amounted to 305 Calories. The heat which theoretic- 

 ally therefore, should have been produced was 4 "4 Calories. 

 SerLnt the calorimeter actually absorbed 395 ! Calorie, ; a j difference 

 between the theoretic and experimental results of ^Calo 





to hold true Inasmuch as the calorimeter of Benedict differs in some re- 



