92 



THE ANIMAL AS A MACHINE. 



evolved at a constant low point on the scale, and these 

 energies are converted into new forms, or into dynamic 

 energy, and applied to the performance of work with- 

 out variation of that temperature. That heat is pro- 

 duced is a matter of constant experience and observa- 

 tion, and we throw off more as we work harder, whether 

 with mind or body, and as we move more rapidly. 

 That this heat, so far as converted into other energies 

 by the body, must be so converted at a sensibly con- 

 stant temperature is obvious from the fact that the 

 change goes on in a mass of circulating fluids ; that 

 this proves that the conversion is not thermodynamic, 

 but is due to some entirely different and unknown 

 method, is equally evident to the engineer, who under- 

 stands that only so could the " law of Carnot " be 

 evaded. That this action is possibly electrodynamic is 

 indicated by the fact that electric currents traverse the 

 system, and that we may at any moment compel the 

 muscles to do work by the application of a current 

 from an external source. 



30. Of the Methods of Production of Energies 

 in the body, we know as yet absolutely nothing ; but 

 we do know that electricity may be produced in large 

 quantity, and at high pressure," as the electrician 

 says, as illustrated by the torpedo and the gymnotus 

 or electric eel ; and the anatomist knows the mechani- 

 cal structure of the organs from which it is evolved, 

 though he is ignorant of the processes therein con- 

 ducted. We also know that the best currents for 

 electrodynamic operations are those of low intensity, 

 such as are easiest of control and insulation in the 

 body. By analogy with the other methods of trans- 

 formation, we may presume that the source of this 



