1 86 Energy stored in the Organism. CHAP. 



for the most part, inhibitory. To go back to our 

 former illustration, it may be compared to the relation 

 of the engineer to the steam-engine ; for this also is 

 regulative and inhibitory. The engineer controls the 

 engine, not by impelling or ceasing to impel it by 

 any force in his own organism, but by permitting, or 

 refusing to permit, the steam to flow into the cylinder, 

 and by directing it on the one side or the other of the 

 piston. 



The way in which it is probable that the Will 

 really acts is, however, quite unlike this. There 

 appears to be conclusive evidence that the animal 

 system has the power of storing energy, which, can be 

 afterwards liberated for the purpose of doing muscular 

 work. 1 The seat of this stored energy is probably the 

 substance of the muscles ; and the Will determines 

 muscular action by determining whether, and at what 

 time, this stored energy shall be transformed, by 

 the contraction of the muscles, into actually working 

 energy. It is true that the determination of the 

 will is conveyed to the muscle, not by any immediate 

 action, but by a current of nervous energy sent 

 downwards from the brain ; the sending of which 

 current involves a transformation of energy, and is as 

 truly a physical agency as the opening or closing of 

 a steam-valve by the engineer. It seems probable 



1 For the facts which prove this, see Carpenter's Human 

 Physiology ; also the account of the experiments of Fick and 

 Wislicenus on muscular work, in the Philosophical Magazine, 

 June 1866. 



