EFFICIENCY OF ISOLATED MUSCLE 



501 



prevented from shortening. On examination of the potential 

 energy developed by a stinuilatcd muscle not allowed to shorten, 

 it was found to be approximately 1/6 Tl, where T = the maximum 

 tension and / = the length of the nuisele. Hill maintains that the 

 true mechanical efficiency can be determined by comparing this 

 quantity with the heat production. This value 1/6 Tl when 

 expressed in heat units is 10~*/-t-26 calories. (See Table XCI.) 

 He found efficiencies approximating 90 per cent, in the initial 

 phases of contraction, and if the whole process, i.e. initial and 

 recovery phases taken together, were assessed, the efficiency, 

 under the conditions of his experiments, was in round figures 

 50 per cent. 



TABLE XCI 



ExPT. — Length of muscles, 3-3 cm. ; weight of muscles, 0-135 gm. ; 

 1 scale division of deflection = 

 contractions. 



Duration of excitation : sees. 

 Initial tension : grm. wt. 

 Heat production H : cal. X 10- 

 Tension T : grms. wt. 

 TII6H . . 



Incidentally he found that different types of muscle {e.g. semi- 

 membranosus and sartorius) definitely differed in efficiency. He 

 also found that the maximum efficiency was only obtained under 

 very special conditions of initial tension, strength of stimulus and 

 the physiological state of the muscle. 



