CHAPTER III. 



THE MEASUREMENT OF ENERGY. 



236. General Remarks. The two forms of energy with which 

 we are concerned in our study of the human machine are, firstly, 

 that which is manifested externally in work or heat, and, secondly, 

 that energy which acts from outside on the organism. 



The first is the expression of physiological work or physiolo- 

 gical energy. The second is due to natural and meteorological 

 actions. The latter react on the former so that the measure- 

 ment of physiological energy, that is to say, of the expenditure 

 of the human motor gives exactly the resultant of its functions 

 at a definite moment. In addition, it indicates the quantity of 

 energy that a certain amount of work entails, a certain form of 

 activity whose mechanical estimation would not be possible. 



This kind of measurement will first be considered. 



237. Measurement of Physiological Energy. There are two 

 methods, that of the maintenance ration and that of the con- 

 sumption of oxygen ( 100). 



(A) Method of Maintenance Rations. The subject of the experi- 

 ment follows his usual alimentary diet. The approximate quan- 

 tity and quality of the rations consumed is noted. Then, by 

 trial, he is given a ration such that every day, at the same hour, 

 his weight is appreciably the same. That hour will be preferably 

 on rising in the morning. 



In addition, if it is desired to find the ration corresponding to 

 a definite dynamic expenditure, the daily work should be as 

 constant as possible., and performed at the same period of each 

 day. 



As soon as the subject has began to work, it may be found 

 that the trial ration may allow him to maintain his weight even 

 on the following day. It would be a mistake to stop there. We 

 have always found that the ration would not maintain the weight 

 on next day but one. It must then be slightly increased. On 

 the other hand, seven to eight days of the same work diminish 

 the living ration. These variations are small, as the following 

 figures show : 



Weight of subject in repose 80-200 kg 



1st day of work 80-200 



2nd 79-980 



80-100 



4th 80-180 



