THE NERVOUS SYSTEM OF MAN. 



65 



sponding motion, or motion initiated without inciting 

 sensation. 



4. The velocity of electricity is always, like all 

 ethereal vibrations, inconceivably great; but the veloc- 

 ity of a nerve current has been measured and found to 

 be very moderate — only about one hundred feet a second. 

 In fact, the phenomena of transmission of nerve influence 

 would suggest an analogy with propagated chemical 

 change, such as combustion of a train of gunpowder 

 rather than electric current. 



But it will be answered that "seeing is believing." 

 The electric organ of certain fishes, as the electric eel, 

 discharges powerful currents — sufficient, indeed, to kill 

 a man. These organs are connected with the brain by 

 very large nerves. The discharge of electricity is cer- 

 tainly under the control of the will. It is an act of 

 volition. The fish is exhausted by it as by any power- 

 ful effort. 



At first sight this seems, indeed, demonstrative ; but 

 not so. All the forces of Nature, nerve force and life 

 force among the number, are correlated — i. e., are con- 

 vertible one into another. Now, the electric organ of 

 a fish constitutes an arrangement for converting nerve 

 force into electricity, precisely as a muscle is an arrange- 

 ment for converting nerve force into mechanical power. 

 We might as well say that nerve force is identical with 

 mechanical power as to say that it is naught else than 

 electricity. 



The fact is, there are many different forms of force 

 in Nature, each producing a peculiar group of phenom- 

 ena, the study of which gives rise to a peculiar depart- 

 ment of science. Now the phenomena of nerve force 

 are so different from those of electricity that these two 

 are rightly called different forms of the universal energy, 

 although, indeed, they are transmutable into one another. 



