Chemical Agents on the Nervous System. 35 



I, therefore, continued my experiments, and finally with 

 complete success. 



Ex. 13. We removed the head of a frog, and denuded the 

 lumbar nerves. 



We passed the direct current from one Voltaic arc of silver 

 and zinc, through these nerves, for four minutes. On break- 

 ing the circle, there were movements of the anterior ex- 

 tremities. 



We again made, and again interrupted, the Voltaic circle ; 

 there were no movements of the anterior extremities. We 

 now remade the circle, and continued its influence for seve- 

 ral minutes ; on breaking it, there were again movements of 

 the anterior extremities. 



This proceeding was repeated again with the same results ; 

 a momentary intermission of the circle was followed by no 

 effect on the anterior extremities on breaking ; the continued 

 Voltaic influence was followed, on breaking, by contraction 

 of their muscles. 



This phenomenon could only arise from the electrogenic 

 state of the incident portion of these nerves. 



Ex. 14. This experiment was repeated. On first making 

 the direct current, as before, there were reflex movements of 

 the anterior extremities. 



On allowing the current to exert its influence during four 

 minutes, and then breaking the circle, there were again 

 movements of the anterior extremities. This was repeated. 

 On remaking and breaking the circle immediately, there 

 were now no movements of the anterior extremities ; but, on 

 continuing the influence of the Voltaic arc for several mi- 

 nutes, and then removing it, there were again movements of 

 the anterior extremities, — the efi*ect of the electrogenic state 

 of the nerves. 



Ex, 15. We repeated this experiment, applying the inverse 

 current. 



There were reflex movements of the anterior extremities 

 on making the circle ; but none on its interruption, after an 

 interval of four minutes. 



It will be remembered that the inverse current is more apt 

 to induce the phenomena of the electrogenic state than the 



