36 



THE ANIMAL AS A MACHINE. 



apparatus for transformation, converting the molecular 

 energy of electricity into the mechanical form in such 

 manner as permits its useful employment. 



These machines, reversed, change the energy of me- 

 chanical power into the electrical form, and both direc- 

 tions of transformation in well-designed machinery 

 result in a very efficient conversion of energy. As a 

 rule, it is found much more satisfactory to derive the 

 energy, initially, from a prime mover, by conversion 

 into the electrical form, than to obtain it directly from 

 the voltaic battery. Water-power or the combustion 

 of fuel is vastly less costly than the combustion of zinc 

 and the saturation of acids with its salts. 



The purpose of this discussion is to describe, briefly 

 and exactly, the characteristics of the animals as motors, 

 to describe their methods of action and their sources of 

 gain and loss of energy, and to present the principles 

 of energy-production and transformation illustrated by 

 them. 



