5o THE ACTIVE FORCES OF LIVING ORGANISMS 



therefore, to regard it as an essential factor in nervous 

 action. 



The chemical element is also essential. Firstly, 

 because sensation is impossible without oxidation in 

 the nerve centres ; and, secondly, because certain forms 

 of sensation are directly due to chemical action at the 

 periphery. Lastly, the electrical element, accom- 

 panying as it does the impulse step by step, must, 

 one would think, for other reasons than that already 

 given, play some part in its transmission. It seems 

 contrary to all reason to suppose that an active force, 

 such as electricity, can be merely passive and exert 

 no influence on such loose and mutuable compounds 

 as those of living tissue. We know that when 

 passed through the tissues from a battery it induces 

 metabolism, and we may therefore infer that when 

 generated in the body it contributes to bring about 

 chemical action, if not in the nerve fibre, at least 

 in the nerve-cell. Indeed, if we adopt the modern 

 view of physicists, that the ether permeates all matter, 

 if we look upon it as being in a state of tension, and 

 if we consider electricity to be a movement in it due 

 to variations in that state, then it will seem impossible 

 that electrical action should take place without 

 reacting on the molecules of the region in which 

 it occurs. We may, indeed, with this torch in our 

 hands, penetrate into the very arcana of nervous 

 action ; for if we suppose a certain number of the 

 molecules of a nerve-cell to be in the act of oxidizing, 

 and to produce thereby variations in the tension of 



