AXIMAL HEAT. 



588 



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 -f 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 heat 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 the 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 

 that tend to excite the animal. The chief sources of error in the calorime- 

 try are in failures to obtain accurate temperatures of the calorimeter and of 

 the animal. In the latter case inaccuracy is to some extent absolutely una- 

 voidable, chiefly because of normal fluctuations which occur frequently and are 

 often very marked. 



Conditions affecting' Heat -production. The quantity of heat produced 

 must necessarily vary with many circumstances. Estimates of heat-production 

 in the adult range in round numbers from 2000 to 3000 kilogramdegrees per 

 diem according to the method and incidental circumstances. Thus, according 

 to 



Scharling 3169 kilogramdegrees 



Vogel 2400 " 



Him 3725 " 



Leyden 2160 " 



Hemholtz 2732 



Bosenthal 2446 " 



Danilesky 3210 



Ludwig . . 3192 " 



Ranke 2272 kilogramdegrees 



Riibner 2843 " 



Ott 103 " 



per hour during the afternoon I weight of 

 man 87.3 kilograms). 



Lichatschew .... 33.072 to 38.723 kilo- 

 gramdegrees per kilogram of body-weight 

 per diem. 1 



The chief conditions which affect heat-prod notion are age, sex, constitution, 

 body-weight and body surface, species, respiratory activity, the condition of 

 the circulation, internal and external temperature, food, digestion, time of day, 

 muscular activity, the activity of heat-dissipation, nervous influences, drugs, 

 abnormal and pathological conditions. 



1 The figures by Ott (Nm York Medical Journal, 1889, vol. 16, p. 29) and Lichatschew 

 (Dia. inauguralis, St. Petersburg, 1893; quoted in Hermann's Jakreabene^te der Physiologic, 

 1893, p. 99) were obtained by means of a water calorimeter. 



