138 NERVE FORCE. CHAP. XI. §. I. 



means of a cork into a glass tube, -which formed the 

 handle ; but, as may be readily supposed, the action 

 of the steel needle upon the needles of the galva- 

 nometer so interfered with the results, that it was 

 obliged to be set aside, and a pointed piece of 

 copper wire, or a piece of glass or a glass pen, was 

 used for the purpose. 



The experiment thus arranged, the nerve was 

 then irritated, and the muscles of the limb made to 

 contract; but no effect occurred upon the needle. 

 When, however, one electrode remained in the 

 nerve, and the other was placed on its external 

 surface, then the ordinary effect, the nerve current, 

 was produced, the nerve during this period not 

 being stimulated to action : if the nerve was stimu- 

 lated and the muscles contracted, there did not 

 appear to be any effect upon the needle indicative of 

 an increase in the nerve current, or even of a sudden 

 decrease in it, the needle gradually receding to its 

 former position. The nerve was divided at its 

 lower extremity, one electrode brought into contact 

 with the divided surface, and the other with the 

 longitudinal surface ; the effects were the same ; the 

 nerve current appeared, but after that, there was no 

 increase or indication of a current upon stimulating 

 the nerve. 



It will be readily seen, that two questions are 

 involved in this last experiment: 1st, Is a nerve, 

 during nerve action, traversed by a current of 

 electricity? which we are now considering: and, 



