600 



AttlMAL HEAT 



[cH. XL 



at rest, estimated in calories.* The table conveniently takes the form 

 of a balance-sheet in which production and discharge of heat are com- 

 pared ; to keep the body-temperature normal these must be equal. 

 The basis of the table in the left-hand (income) side is the same as 

 Kanke's diet (see p. 587) : 



Production of heat. 



Metabolism of Calories. 



Proteid (100 gr.) . 100x4000= 400,000 



Fat (100 gr.) . 100x9400= 940,000 



2,380,000 



Discharge of heat. 



Warming water in food, 



2 -6 kilos. x25C.= 

 Warming air in respiration, 



16 kilos, x 25 x 0-24 = 

 Evaporation in lungs, 



630 gr. x 582 = 



Radiation, evaporation, etc., 

 at surface, plus the thermal 

 equivalent of mechanical 

 work done accounts for the 

 remainder . 



65,000 



96,000 



366,660 



1,852,340 



2,380 ; 000 



The figures under the heading Production are obtained by multi- 

 plying the weight of food by its physiological heat-value. The 

 figures on the other side of the balance-sheet are obtained as follows : 

 The water in the food is reckoned as weighing 2'6 kilos. This is 

 supposed to be at the temperature of the air taken as 12 C. ; it has 

 to be raised to the temperature of the body, 37 C., that is, through 

 25 C. Hence the weight of water multiplied by 25 gives the number 

 of calories expended in heating it. The weight of air is taken as 

 weighing 16 kilos. ; this also has to be raised 25 C., and so to be 

 multiplied by 25 ; it has further to be multiplied by the relative heat 

 of air (0'24). The 630 grammes of water evaporated in the lungs 

 must be multiplied by the potential or latent heat of steam at 37 C. 

 (582) ; the portion of heat lost by radiation, conduction, and evapora- 

 tion from the skin constitutes about four-fifths of the whole, and is 

 obtained by deducting the three previous amounts from the total. 

 This table does not take into account the small quantities of heat lost 

 with urine and faeces. We are further supposing that the man 

 remains of constant weight, so that there is no storage or loss of 

 material, and, therefore, of energy in the body. He is also supposed 

 to be at rest, and therefore the amount of work done is only what is 

 called internal work, i.e., maintaining the circulation, respiration, etc. 



It need hardly be remarked that the above is a mere illustrative 

 experiment. Changes in the diet, in the atmospheric temperature, in 

 the temperature of the food taken, in the activity of the sweat-glands, 



* The calorie we are taking is sometimes called the small calorie ; by some the 

 word calorie is used to denote the amount of heat necessary to raise one kilogramme 

 of water 1 C. 



