IS THE BODY A MACHINE? 37 



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 that 

 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 conform 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 concerning the details of the action 

 of the living machine. We have a clear under- 

 standing of the method of action of a steam 

 engine. Its mechanism is simple, and, moreover, 

 it was designed by human intelligence. We can 

 understand how the force of chemical affinity 

 breaks up the chemical composition of the coal, 

 how the heat thus liberated is applied to the 

 water to vaporise it ; how the vapour is col- 

 lected in the boiler under pressure; how this 

 pressure is applied to the piston in the cylinder, 

 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 



