WORK PRODUCTION 549 



be reduced to zero, as for example in horizontal locomotion, 

 the gross efficiency of course also becomes zero. 



650. Efficiency per day. The figures for either gross or 

 net efficiency show the efficiency for the time during which the 

 work is being done. Since, however, it is not practicable to stop 

 the animal machine when the demand for -work ceases, the 

 efficiency for the entire 24 hours, i.e., the degree to which the 

 body energy is utilized in practice, will evidently vary with 

 the number of hours work done per day. Thus if Benedict and 

 Cathcart's subject had been able to work 8 hours per day at 

 the same rate as in the experiment just cited, his gross efficiency 

 for the 24 hours would have been as follows : 



Energy expended 



480 minutes work @ 6.32 Cals. = 3034 Cals. 



960 minutes rest @ 1.09 Cals. = 1046 Cals. 



4080 Cals. 

 Work done 



480 minutes @ 1.02 Cals. = 490 Cals. 



Efficiency per day 12.01 per cent 



On the other hand, if he had worked only one hour per day, 

 it may be presumed that both the net and gross efficiency of the 

 work production during the hour of work would have been 

 substantially the same but the efficiency for the 24 hours would 

 have been much lower, viz., 



Energy expended 



60 minutes work @ 6.32 Cals. =379 Cals. 

 1380 minutes rest @ 1.09 Cals. = 1504 Cals. 



1883 Cals. 

 Work done 



60 minutes work @ 1.02 Cals. = 61 Cals. 

 Efficiency per day 3.24 per cent 



In discussions of the efficiency of a man or an animal as a 

 motor, a,nd particularly in comparisons with artificial motors, 

 it is essential to distinguish clearly whether the net, or the gross 

 efficiency is meant and likewise to base the comparisons upon 

 the performance per day. Since the net is apparently less 

 affected than the gross efficiency by variations in the intensity 

 and duration of the work, it appears to be the most logical 



