26 THE STORY OF THE LIVING MACHINE. 



give a means of determining the proportion of 

 the energy furnished in the form of food which 

 can be utilized in the form of motive force. This 

 figure appears to be decidedly larger than that 

 obtained by any machine yet devised by man. 



The conclusion of the matter up to this point 

 is then clear. If we leave out of account the 

 phenomena of the nervous system, which we shall 

 consider presently, the general income and outgo of 

 the body as concerns matter and energy is such tliat the 

 body must be regarded as a machine, which, like other 

 machines, simply transforms energy without creating 

 or destroying it. To this extent, at least, animals con- 

 form to the law of the conservation of energy and are 

 veritable machines. 



Details of the Action of the Machine. We turn 

 next to some of the subordinate problems concern- 

 ing the details of the action of the living machine. 

 We have a clear understanding of the method of 

 action of a steam engine. Its mechanism is simple, 

 and, moreover, it was designed by human intelli- 

 gence. We can understand how the force of 

 chemical affinity breaks up the chemical com- 

 position of the coal, how the heat thus liberated is 

 applied to the water to vapourize it ; how the va- 

 pour is collected in the boiler under pressure ; how 

 this pressure is applied to the piston in the cylin- 

 der, and how this finally results in the revolution 

 of the fly-wheel. It is true that we do not under- 

 stand the underlying forces of chemism, etc., but 

 these forces certainly exist and are the foundation 

 of science. But the mechanism of the engine is 

 intelligible. Our understanding of it is such that, 

 with the forces of chemistry and physics as a foun- 

 dation, we can readily explain the running of the 

 machine. Our next problem, therefore, is to see 



