Ill THK XKRVOUS SYSTK.M AM) ITS COXSKUVATK i\ 



ordinary electric current. 1 It lias no such inconceivable 

 velocity. About the middle of the last century Helm- 

 holtz reported that he had measured the rate at which 

 the impulses pass in the nerves of frogs and that he had 

 found it to be less than 100 feet per second. Recent 

 studies have made it probable that it is considerably 

 higher in man, but it is not by any means equal to the 

 -peed of sound-waves in the air. 



A most important question, and one which is proving 

 difficult to answer, relates to the part played by the peri- 

 karya when impulses are passing. Do these spend their 

 own substance to reinforce the transmission? If they do 

 they are like the relay cells in telegraphic systems. Wires 

 are not worn out with carrying electric currents, but 

 batteries are used up in generating them. It has been 

 the common belief that the pcrikarva of the gray matter 

 do suffer disintegration when the neurons to which they 

 belong are active. It is usual to say that when a neuron 

 i- stimulated through its dendrites there is a discharge, 

 meaning by this an evolution of fresh energy at the cost 

 of material oxidi/ed or otherwise degraded. Assuming 

 this to be true, we shall have an outflow of energy greater 

 than that applied as a stimulus. 



We could, perhaps, imagine a nervous organization 

 such that no energy save that originally applied by the 

 external stimulus should be observed to flow from it. 

 This would be economic to the last degree. Hut it seems 

 unlikely that any tissue can ever become so specialized 

 as to lose all trace of its primitive tendency to undergo 

 some decomposition as a necessary part of its activity. 

 When contractile elements are stimulated they respond 



'Two investigator-, ( 'rehore and Williams, of New York, liavr 

 recently attradi'il much notice by their contention that nerve- 

 im|> il-e- arc actually electric in their nature. Hy taking into account 

 the dimen-ioii- dl the fibers and assigning certain physical proper- 

 tie- to the sheaths they put lort h all ariillllient to prove that electric 

 disturbance- should not pass very rapidly in nerves, but rather at 

 about the velocity found to hold for the nervc-implllses. It is too 

 soon to -;i\ \\hether phy-iolo^i.-ts \\ill generally be \\oii to this con- 

 cept ion 



