32 On the Effects of Certain Physical and 



of the arc of zinc and silver, the silver being under the lumbar 

 tissues : 



In four minutes we raised the spinal marrow from the 

 zinc ; there was tetanus. 



We again raised it in five minutes more, and then divided 

 the spinal marrow close to its lower part ; the tetanus ceased 

 instantly. 



Ex. 8. If the frog be prepared as in fig. 2, and the Voltaic 

 circuit be inverse or upward in the spinal marrow ; and if a 

 and c be connected, there are movements in the correspond- 

 ing extremities ; viz., a and c ; \i b and d be connected there 

 are movements in b and d\ and on breaking the circuit there 

 is tetanoid spasm in the lower extremities c and d. 



On reversing the Voltaic current and breaking the circuit, 

 there was no tetanus. 



On recompleting the circuit and connecting the Voltaic 

 wires, there were strong movements in all the limbs. On 

 breaking the circuit and connecting, there were still move- 

 ments, but they were slight. 



Ex. 9. — On repeating the experiments described in fig. 2, 

 with the inverse current, there were movements in all the 

 limbs on connecting e and /; on connecting e or / and a, 

 there were movements in a ; on connecting e oy f and b in 

 b ; e or /and c in c ; e or/ and d in d ; on connecting a and 

 c, b and d, a and 6, and c and d, no effect was observed. 



II. On the Electrogenic State of Incident Nerves. 



The physiologist acquainted with the recent progress of our 

 knowledge of the nervous system will readily imagine the im- 

 portance of the next question to be submitted to the Society, 

 viz., whether the incident spinal nerves, as well as the spinal 

 centre itself and the muscular nerves, are susceptible of the 

 electrogenic state, with its independent phenomena. 



It was difficult to submit this question to the test of expe- 

 riment. It was difficult to denude and isolate incident spinal 

 nerves of adequate magnitude. At length it was found, that 

 if a portion of integument over the dorsal region of the frog 

 was detached by incision from the rest, and gently raised, 

 several pairs of nerves were discoverable proceeding from the 



