ALIMENTATION AND THE EXPENDITURE 151 



after its passage, and the quantity of water finally condensed in 

 the room give the total weight of water evaporated by the lungs 

 and exuded by the skin (perspiration). It is thus possible for the 

 experimentalist to note and calculate the energetic expenditure 

 of a subject in a determined time, either in repcse (static value) 

 or at work (supplementary or dynamic expenditure). 



The accuracy of the apparatus, especially for static evaluations, 

 is such that the combustion of alcohol therein gives the same heat 

 of combustion as that found by the calorimeter. 



In addition to the expenditure we have to determine the ener- 

 getic value of the alimentary ration when properly metabolised. 

 To effect this, the ration is analysed in samples, and its total heat 

 of combustion determined ; that of the urine and rejected faeces 

 is deducted. The equations of combustion are then utilised, 

 the weight of the oxydised proteids being calculated according to 

 the weight of " urea " contained in the urine, and the weight of 

 the fats according to that of the carbon in the expired gases 

 (CO 2 ), a deduction being made from the carbon of proteid origin. 

 Atwater presumed that carbo-hydrates, in reserve in the cells, 

 were not acted upon.f 1 ) This postulate has been confirmed 

 by experiment in the case of rations containing a sufficient 

 quantity of carbo-hydrates. 



Knowing the quantity and quality of all the substances utilised 

 in the physiological labour of the subject, we can calculate 

 the expenditure exactly. A comparison of the latter with the 

 measured expenditure proves that the " principle of the conserva- 

 tion of energy " is fully applicable. The results of several 

 hundreds of experiments, of a duration of 1 to 4 days each, on six 

 to seven different subjects agreed very satisfactorily. 



Thus the calorimetric chamber, being kept at 20 C, the results 

 were : 



Bulletin, No. 136, p. 125. 



