ASSESSMENT OF EFFICIENCY 



393 



of muscular activity, it is true, is not yet clear, but it may be 

 stated with a considerable degree of certainty that, whatever the 

 type of change which takes place, all the experimental evidence 

 available points to the muscle not being a heat engine. The 

 majority of workers now look upon muscle as a chemical machine 

 which works at a relatively constant temperature. 



On the purely experimental side much work has been done on 

 the determination of the efficiency both of isolated muscle and of 

 the body as a whole. 



If the organism be considered as a whole and its efficiency 

 determined, it is found that, although it is high, it is never as 

 high as the results which have been obtained experimentally with 

 isolated muscle. This result is not to be wondered at when the 

 methods of attacking the problem are considered. In the case of 

 the isolated muscle, its position, the amount of work to be done 

 and the mode and time of stimulation can all be accurately 

 controlled, conditions which are, for the most part, lacking when 

 the whole organism has to be dealt with. 



Modern work has shown very considerable agreement as regards 

 the degree of efficiency, as is shown by the following table : 



TABLE LXXVII. 



GROSS AND NET EFFICIENCY OF THE BODY AS A WHOLE. 



The outstanding difficulty in the assessment of the net efficiency 

 is the selection of the proper base line for comparison. It is 

 immaterial whether the work done be that of marching or mountain 

 climbing, of turning an ergostat or a bicycle ergometer, the same 

 difficulty crops up. As the bicycle ergometer has been most fre- 

 quently used in the modern experiments it will be dealt with lu re. 



In the determination of the mechanical efficiency with this 

 machine no less than five base lines may be used though they are 



