CHAP. XI. §. n. THE BALVANOSCOPIO FEOG. 141 



upon is, by occasionally trying the limb with some 

 well-known source of electric action, such as the 

 muscle or nerve, and to have several at hand in case 

 of emergency. 



The former experiments were now repeated, and 

 the nerve of the galvanoscopic frog, its limb being 

 supported on a piece of glass, was laid at one time 

 transversely on the sciatic nerve, at another time 

 longitudinally on the nerve, and the nerve then 

 irritated as before, but no effect occurred upon the 

 galvanoscopic limb. If the galvanoscopic nerve be 

 placed carelessly upon the other nerve, so that its 

 end and side touch the nerve, and thus form a 

 circuit, then the galvanoscopic limb will contract, 

 this being the result of the nerve current in the 

 galvanoscopic frog acting upon its own muscles; 

 the effect being over, and the nerve remaining in 

 this position, no contraction occurred upon stimu- 

 lating the sciatic nerve ; but upon opening the circuit 

 of the nerve, it occasionally happened, if the frog 

 was delicate in its indications, that contractions 

 ensued. Should there be any blood upon the nerve 

 of the animal, and the nerve of the galvanoscopic 

 limb touch it and the nerve, then the galvanoscopic 

 limb will contract; this may be considered as the 

 result of a current arising from the contact of hete- 

 rogeneous substances. But in neither instance was 

 the effect any thing like that which occurs when 

 the galvanoscopic nerve is placed upon a tetanized 

 muscle. 



