Chemical Agents on the Nervous System. 259 



less traversed the surrounding humid tissues; we then caused 

 that influence to pass from c to d, now including within it 

 the isolated brachial and lumbar nerves. Having waited three 

 minutes only, we had energetic spasmodic contractions in all 

 the extremities on breaking the circuit, less marked, of course, 

 in the anterior than in the posterior. 



On recompleting the circuit, all spasmodic action ceased ; 

 aud on continuing its influence during three minutes, and 

 again breaking it, the same phenomena were reproduced. 

 The experiment was repeated with the same efi'ect. 



In this experiment, as in so many others, the spasmodic 

 action still continued on dividing the lumbar nerve at e, but 

 instantly ceased on dividing it at/. 



This experiment and that represented in fig. 1, concur with 

 that designated the " alternative Voltaique," to demonstrate 

 the influence of surrounding moisture in preventing the spas- 

 modic effects of the electrogenic condition of the nerve, so re- 

 markable when this latter is insulated. 



Ex. 2. We prepared a frog as represented in fig. 1, re- 

 moving the head and viscera, but leaving the brachial and 

 lumbar nerves in contact with the humid tissues underneath. 

 The platinum wires being applied to the lumbar nerves, one 

 near the spine, the other near the femora, and being uncon- 

 nected with the Voltaic arrangement, we brought them into 

 mutual contact, at various distances from the animal, and 

 then connected them variously, by means of a separate piece 

 of platinum wire laid across them ; no obvious effect was 

 produced. 



This proceeding, to obviate circumlocution, I shall here- 

 after designate connecting the wires. I shall also use the 

 phrase " making and breaking" the Voltaic circuit, for the 

 completion or interruption of that circuit. 



We now instituted the Voltaic circuit ; a slight movement 

 was observed in the limbs ; we then connected the wires. The 

 circuit being complete, the movements of the limbs were 

 lively. 



We broke the Voltaic circuit and again connected the wires ; 

 the same lively movements were observed. These move- 



