326 THE PHILOSOPHY OF BIOLOGY 



weight to the top of a hill, or that which raises a 

 pendulum to the highest point of its swing, apparently 

 disappears. If we pass a current of electricity through 

 water, energy disappears, for it requires more current 

 to pass through water than through a piece of metal 

 of the same section. In these and similar cases physics 

 invents potential energies in order to preserve the 

 validity of the law of conservation. The kinetic energy 

 of the weight, or that of the swinging pendulum, be- 

 comes the potential energy of the weight resting at 

 the top of the hill, or that of the bob of the pendulum 

 at its highest point, while the electrical energy that 

 has apparently been lost becomes the potential energy 

 of the changed positions of the molecules of oxygen 

 and hydrogen. This assumption that the visible 

 kinetic energy of motion becomes converted into the 

 invisible potential energy of position is justified by our 

 experience, for (neglecting dissipation) we can recover 

 this lost energy, in its original quantity, from the con- 

 dition of the bodies which became changed physically 

 when the kinetic energy disappeared. Apply the same 

 method to the phenomena of the organism and suppose 

 that the chemical potential energy of the food con- 

 sumed becomes converted into the kinetic energy of 

 motion of the parts of the body : we are justified in this 

 assumption by the results of physiology. But then 

 some of this chemical energy undergoes a transforma- 

 tion of quite another kind and becomes the " biotic 

 energy," which is apparently that which is in us which 

 enables us to perform regulations, or establishes that 

 condition which we call consciousness. We cannot say 

 exactly what this " biotic energy " is, or what are t'^-e 

 steps by which the energy of food becomes converted 

 into it ; but no more can we say what is electrical 

 energy, nor what are the steps by which chemical energy 



