500 



THE EFFICIENCY OF THE ORGANISM 



naturally an increase in the amount of the total work done, the 

 effective muscular work per revolution decreases as the speed 

 increases, and there is therefore a steady fall in efficiency (see Fig. 

 101). The same result is obtained when the speed is varied, with, 

 however, approximately the same production of effective muscular 

 work in the two experiments, as shown in Table XC. : 



* Base line — complete rest, lying. 



As regards the work which has been carried out on isolated 

 muscle, the results which have been obtained are of great interest, 

 as they have led to fresh consideration of the nature of the 

 muscular machine. A. V. Hill, in a long series of ingenious and 

 striking experiments, using special methods of his own devising, 

 has shown that the solution of the problem is not quite so simple 

 as it was formerly imagined. Hill found the simple determination 

 of the mechanical efficiency, i.e. VV/H, the heat equivalent of the 

 work done, divided by the energy output determined as heat, 

 was of no real im])()rtance. The true efficiency of the nniscle is 

 the ratio between the " potential energy thrown into an active 

 muscle by excitation " and tlie " total chemical energy liberated 

 as heat." He found, further, that the heat production varied 

 according to whether the nnisclc was, or was not, allowed to 

 shorten on stimulation. If shortening were permitted the heat 

 output might be 30 per cent, smaller than if the muscle was 



