THE TOTAL EXCHANGES OF THE BODY 



621 



of the faeces formed under the same diet was 1854 calorie for each gramme of 

 protein. Rubner further reckoned that a certain amount of heat would be 

 required for the solution of the proteins and of the urea, and reckoned this 

 at 0-05 calorie. The reduced or physiological heat- value of protein is there- 

 fore equal to 5-345 - (1-0945 + 0-1854 + 0-05) = 4-015 calories. 



A determination of the heat-values of the various food-stuffs shows 

 minute differences between individual members of the same class. Since it 

 is impossible to reckon out accurately the relative amounts of the different 

 kinds of protein, carbohydrate, &c., contained in each diet, Rubner has 

 calculated the average physiological heat- values of the three classes of food- 

 stuffs. These figures have been universally adopted, and are as follows : 



1 grm. protein =4-1 calories 



1 grm. fat = 9-3 



1 grm. carbohydrate =4-1 



Careful experiments have shown that just as there is no loss of matter 

 in the body, so also the sum of the energies put out by the body is equal to 

 the sum of the energy obtained by the oxidation of the tissues and of the 

 food-stuffs in the body during the same time. In an earlier chapter I have 

 quoted the results of an experiment by Rubner on a dog, which demonstrated 

 this equivalence, as proving the important fact that the fundamental 

 doctrine of the Conservation of Energy applies to the organised as to the 

 inanimate world. Similar results have been arrived at by Atwater in a 

 series of experiments with a special calorimeter on man. It may be sufficient 

 here to give the figures from one such experiment : 



