Chemical Agents on the Nervous System. 31 



brae in a frog, and then the lateral and posterior parts of the 

 bony canal, so that the spinal marrow was denuded on all 

 sides. We placed the upper part of this organ on a piece of 

 platinum connected with the silver end of the " courounne de 

 tasses,'' and placed the other wire under its lowest part, so 

 that the direct current passed along it. Tetanoid contrac- 

 tion were observed on " breaking'"* the circuit in twenty 

 minutes. 



After discharging this condition of the spinal marrow, by 

 connecting the wires after breaking the circuit, we could not 

 succeed in reproducing the electrogenic state by the direct 

 current. On reversing the current and breaking it after a 

 time, movements were observed, but no tetanoid condition. 



This phenomena was still more marked on connecting the 

 wires, both before and after breaking the circuit, rather less 

 in the latter case, and ceasing after several repetitions of the 

 connections. 



Ex. 6. We successfully divided and detached the spinal 

 marrow, and laid it over the Voltaic arc, the upper extremity 

 on the zinc, the lower in contact with the silver, so that the 

 current through it was direct. In four minutes there was 

 the most distinct tetanus on hreaking^ which ceased on re- 

 making the circuit. 



This was repeated in five minutes more. 



We then reversed the order of the Voltaic arc and the 

 current; the tetanus continued for several minutes, ceasing 

 gradually. 



Now, on breaking, the tetanus was renewed, but in a modi- 

 fied form, and it did not immediately cease on renewing the 

 circuit, but subsided gradually. 



A few minutes after the subsidence of the tetanus, fresh 

 tetanoid spasm was induced on breaking the circuit, now in- 

 stantly ceasing or remaking it. 



On again reversing the current, energetic tetanus occurred 

 on breaking the- circuit after a time, which instantly ceased 

 on dividing the spinal marrow at its lowest part. 



Ex. 7. We removed the head, and having laid bare the spi- 

 nal marrow, by removing the anterior bodies of the vertebrae, 

 raising it from the spinal canal, placing it on the zinc part 



