CHAP. XI. NOT CUBBENT FOBCE. 147 



than when it travels in the contrary direction. This 

 is equally a natural consequence of the fact, that the 

 particles of the' nerves upon vsfhieh the immediate 

 action of the brain must be exerted, being the 

 interior which penetrate into it more deeply, have 

 their negative poles free. 



" If, instead of coming from the brain, the action 

 exerted upon the nerve comes from the muscle, the 

 polarisation of the nerve must take place in a 

 contrary direction, namely, so that the positive poles 

 are all turned towards the side of the nervous 

 centre, and the negative towards the side of the 

 muscle whence the excitation comes." I have 

 quoted these observations at some length, as con- 

 taining perhaps the most recent views upon the 

 subject, and supported by an authority of some 

 weight. Now the only conclusion that appears to 

 me that can be drawn from these remarks is this, 

 that the force transmitted along a nerve during nerve 

 action is identical with current force as it exists in a 

 wire carrying a current of electricity. If so, I need 

 scarcely add, that we ought to be enabled to obtain 

 some direct earperimental evidence in support of this 

 opinion : at the present time I know of none beyond 

 that advanced by Du Bois Eeimond, who appears to 

 have ascertained in his experiments, that the nerve 

 current may be made to increase or diminish accordaig 

 as the nerve is excited by an electric current — being 

 increased if the cmrent passes in one direction, and 

 diminished if it passes in the contrary du-ection. 



