62 THE STORY OF LIFE'S MECHANISM. 



mental side of the living machine has not been 

 included within the conception of the mechanical 

 nature of the organism. 



THE LIVING BODY IS A MACHINE. 



Eeviewing the subject up to this point, what 

 must be our verdict as to our ability to under- 

 stand the running of the living machine 1 In 

 the first place, we are justified in regarding the 

 body as a machine, since, so far as concerns its 

 relations to energy, it is simply a piece of 

 mechanism complicated, indeed, beyond any 

 other machine, but still a machine for changing 

 one kind of energy into another. It receives 

 the energy in the form of chemical composition 

 and converts it into heat, motion, nervous wave 

 motion, etc. All of this is sure enough. Whether 

 other forms of nervous and mental activity can 

 be placed under the same category, or whether 

 these must be regarded as belonging to a realm 

 by themselves and outside of the scope of energy 

 in the physical sense, cannot perhaps be yet 

 definitely decided. We can simply say that 

 as yet no one has been able even to conceive 

 how thought can be commensurate with physical 

 energy. The utter unlikeness of thought and 

 wave motion of any kind leads us at present 

 to feel that on the side of mentality the com- 

 parison of the body with a machine fails of 

 being complete. 



In regard to the second half of the question, 

 whether natural forces are adequate to explain 

 the running of the machine, we have again 



