THE TOTAL EXCHANGES OF THE BODY 695 



is therefore equal to 5-345 - (1-0945 -f 0-1854 + 0-05) = 4-015 

 calories. 



A determination of the heat- values of the various food-st nil's 

 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 experi- 

 ment 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 suffi- 

 cient here to give the figures from one such experiment : 



