Chemical Agents on the Nervous System. 263 



tinum plates; the muscles of both limbs were now affected 

 with spasmodic contractions. , ^i • 



From this experiment, it would appear that though the m- 

 fluence was so diffused as not to induce spasmodic action on 

 connecting the platinum plates, it was not entirely discharged. 



Ex 6 We now placed a plate of platinum on one nerve 

 of a frog, prepared as in fig. 4, and another under the foot, 

 and completed the Voltaic circuit. When this circui was 

 broken, and the platinum plates were connected, both limbs 



were moved. . , . i? xu„+ 



Hence, we may conclude, that the electrogenic state of that 

 one nerve is sufficient to affect, in its discharge, both limbs. 

 Ex 8 We now changed the form of the Voltaic apparatus, 

 and instead of using the two cells of the " couronne de 

 tasses," we applied an arc of zinc and silver, so as to mclude 

 the nerves in the Voltaic circuit. 



If we used the frog prepared as in fig. 1, we had no spas- 

 modic effect on breaking the circuit. But if we placed the 

 zinc portion of the arc under the lumbar nerve of a frog, pre- 

 pared as in fig. 6, and the silver portion over the femoral 

 muscles, securing perfect contact, we had the most extraor- 

 dinary convulsive and tetanoid conditions of the muscles, on 

 breakino- the Voltaic circuit, which ceased instantly on re- 

 makinglt. The same phenomena were observed in another 

 froo-, on placing the silver portion of the arc on the nerves 

 and the zinc on the muscles, thus reversing the direction of 



the current. . 



In these two cases we divided the nerves, first near the 

 spine, and then near the femora, with the results of per- 

 sistence of the spasmodic action in the former instance, and 

 its instant cessation in the latter. In either case, when the 

 nerve is under electrogenic influence, and the tetanoid state 

 is most marked on breaking the circuit, ceasing when that 

 circuit is renewed, as before; it still continues on -mak- 

 ing the circuit in the reversed direction, that is, on rever- 

 sing the relative positions of the zinc and silver plates of the 



arc. , 



Ex. 9. If, instead of applying the zinc on the nerves, and 



