660 ANIMAL HEAT 



founded on the heat of combustion of the food substances. From 

 careful experiments, it has been found that a gramme of dry protein 

 (egg- albumin), when burned in a calorimeter, yields 5735 calories 

 of heat, a gramme of dextrose 3742, and a gramme of animal fat 

 o/^oo calories (Stohmann). 



Calories. 



Heat-equivalent of i gramme of albumin - 5 '735 



Albumin (minus urea produced from it) - 4*949 



Cane-sugar 3*955 



Kreatin (water-free) 4* 2 75 



Starch 4* 182 



In applying such results to the calculation of the heat-production of 

 the body, it is not sufficient to deduct from the heat of combustion of 

 the proteins the heat which the residual urea would yield if fully 

 oxidized. For other incompletely oxidized products arise from pro- 

 teins when consumed in the body, and Rubner has shown, by actually 

 determining the heat of combustion of the urine and faeces, that the 

 real equivalent of a gramme of albumin is at most only 4*420 calories. 

 The heat-equivalent of our less liberal specimen diet (p. 613) will be 

 approximately : 



Calories. 



Protein, 95 grammes x 4-420 4*9*9 



Fat, 80 grammes x 9- 500 760-0 



Carbo-hydrate (reckoned as 



dextrose), 320 grammes x 3*74 2 I ' I9 Zll 



2 >377'3 



The heat-equivalent of the more generous specimen diet (p. 614) would 

 be 2,878 calories. 



But this is the diet of a man doing a fair day's work, and to get the 

 quantity of energy which actually appears as heat, the heat-equivalent 

 of the mechanical work performed must be deducted. A fair day's 

 work is about 150,000 kilogramme-metres that is, an amount equal 

 to the raising of 150,000 kilogrammes to the height of a metre. Now, 

 a kilogramme-degree or calorie of heat is equivalent to 425-5 kilo- 

 gramme-metres of work, and a kilo gramme -met re to calorie. 



4 2 5 5 I 



The heat-equivalent of the day's work is, therefore, 1 50,000 x ^- = 



352 calories. Deducting this from the heat-equivalent of the food, 

 we get in round numbers 2,520 large calories as the heat given off on 

 the more liberal diet. This corresponds fairly well with the calculated 

 heat-loss (p. 658). 



The table on p. 661, based on the direct calorimetric observations 

 of Atwater and Benedict, shows the average heat-production in a large 

 number of experiments on several individuals at rest and doing measured 

 amounts of work, with a stationary bicycle, for instance. This was 

 connected with a small dynamo, which transformed the greater part 

 of the work into electrical energy. The electrical energy in its turn 

 was changed into heat, the current passing through a lamp. 



The heat-production during the hours of sleep, in the second night 

 period, is much less than in the waking hours of rest, and of course 

 enormously less than in the hours of work. After work the heat pro- 

 duction in the period of sleep is only a little greater than after rest. 



As already indicated (p. 659), it is permissible to calculate the heat- 



