ANIMAL HEAT. 481 



of water in the samples of the air passiug into and from the calorimeter, and 

 estimating from these results the amount of moisture imparted to the total air 

 leaving the chamber. Assuming that 10 grams of water were thus evaporated, 

 since each gram requires about 582 calories or 0.582 kilogramdegree, the quan- 

 tity of heat evolved would be equal to 10 X 0.582 = 5.82 kilogramdegrees. 



The total quantity of heat dissipated would therefore be the sum of the 

 quantities given to the calorimeter, to the air, and to the water evaporated : 



Given to the calorimeter 54,001) kilogramdegrees. 



Given to the air 5,152 " 



Lost in evaporating water 5,820 



Total heat-dissipation ti4/J72 " 



The quantify of heat produced is determined by adding to or subtracting 

 from the quantity dissipated the amount of heat that may have been gained 

 or lust by the organism. It is obvious that any difference between the 

 quantities of heat dissipated and produced must be represented by an increase 

 or decrease of the mean temperature of the animal. If the animal's tempera- 

 ture remains unchanged, the quantity of heat produced is the same as the 

 quantity lost; if, however, the animal's temperature increases, less heat is 

 dissipated than is produced ; if it falls, vice versa. The quantity of heat 

 involved in a change of body-temperature is determined by the product of 

 the change in temperature into the animal's weight and specific heat. Assum- 

 ing that the animal's temperature at the beginning of the experiment was 

 38.95° C. and at the end 39.32° C, the temperature being increased 0.37° C, 

 that the animal's weight was 25 kilograms, and that the animal's specific heat 

 was 0.8, the quantity of heat would be 0.37 X 25 X 0.8 = 7.4 kilogramdegrees. 

 The quantity of heat produced would, therefore, be the total quantity dissipated 

 plus the quantity of heat added to the heat of the organism at the time the 

 experiment begun ; therefore, the heat-production was 64.972 -\- 7.4 = 72.372 

 kilogramdegrees. If the animal's temperature had fallen, more heat would 

 have been dissipated than produced, because the total quantity of heal in the 

 organism was greater at the beginning than at the end of the experiment ; 

 therefore, the quantity of heat represented in the change of temperature would 

 have been deducted from the quantity of heat dissipated. 



While calorimetric experiments do not generally involve any special diffi- 

 culties, accurate results can only be ensured by the strict observation of certain 

 details: (1) The temperatures of the calorimeter and room should be as nearly 

 as possible alike and kept as far as possible constant. (2) The thermometers 

 employed should be SO sensitive that readings can be made in hundredths of a 

 degree, and they should respond very quickly, SO that rectal temperatures can 

 be obtained within three minutes. (3) Rectal temperatures are to be preferred, 

 the thermometer always being inserted to the same extent and held in the 

 same position, care being exercised to prevent the burying of I he bulb in fecal 

 matter. (4) The animal during the taking of its temperature must on no 

 account be tied down, but gently held, and all circumstances seduously avoided 

 Vol. r.— 31 



