ANIMAL HEAT. 587 



definite Dumber of degrees gives off a definite quantity of heat. The heat thus 

 generated by the oxidation of the alcohol or hydrogen or given off by the cool- 

 ing of the water is imparted to the calorimeter and increases its temperature. 

 Knowing the quantity of heat given to the calorimeter and the increase of 

 temperature of the instrument, the determination of the calorimetrical equiva- 

 lent may be easily made. Thus, 1 gram of alcohol yields in round numbers 

 9000 calories ; if we burn 10 grams of absolute alcohol, 90,000 calories will 

 result; if the temperature of the calorimeter be increased 1, the calorimetric 

 equivalent will be 90,000 calories or 90 kilogramdegrees ; in other words, for 

 each degree of increase of the temperature of the calorimeter a quantity of 

 heat equivalent to 90 kilogramdegrees is absorbed. 



The heat dissipated by an animal is only in part absorbed by the calori- 

 meter, another portion being given to the air which passes from the instrument, 

 and another portion to water which is evaporated from the lungs and skin. 

 Three estimates, therefore, are necessary (1) of the heat given to the calori- 

 meter, (2) of the heat given to the air, and (3) of the heat given off in the 

 evaporation of water. 



The estimate of the heat given to the air necessitates the measurement of 

 the quantity of air supplied to the calorimeter, and of the temperature of the 

 air on entering and leaving the calorimeter ; while the estimate of the heat lost 

 in evaporating water involves the measurement of samples of the air entering 

 and leaving the instrument and of the quantities of water in both cases, the 

 total quantity of water evaporated from the animal being estimated from these 

 data. 



The conduct of such experiments is not attended with any material dif- 

 ficulties. The water of the calorimeter is stirred for a sufficient length of 

 time in order to obtain a uniform temperature. The temperature of the 

 animal is taken and the animal then placed within the animal chamber. The 

 temperatures of the calorimeter and of the air entering and leaving the instru- 

 ment, and readings of the three gas-meters are recorded. During the progress 

 of the experiment air temperatures are recorded at regular intervals of ten or 

 fifteen minutes and the water stirred for a few seconds each time. At the 

 conclusion of the experiment there are recorded the temperature of the calori- 

 meter, the temperatures of the air entering and leaving the calorimeter, the 

 quantities of air passing through the three gas-meters, and the temperature of 

 the animal. 



The quantity of heat given to the calorimeter is now determined by multi- 

 plying the increase of temperature of the instrument by the calorimetric 

 equivalent. If the rise of temperature be 0.6 C. and the calorimetric equiva- 

 lent be 90 kilogramdegrees, the quantity of heat imparted to the water jacket 

 will be 90 X 0.6 = 54 kilogramdegrees. 



The quantity of heat imparted to the air is determined by finding first the 

 corrected volume of the air, then reducing the corrected volume to weight, 

 then multiplying the weight by the specific heat of air at C., and finally 

 multiplying by the increase of temperature. The corrected volume may be 



