208 ELECTRIC FISHES. LfiCT. X. 



of the discharge, indicates a determinate direction in the 

 action of the nervous force ; and there appears some 

 foundation for this supposition, when we consider that the 

 excitation of the fourth lobe, and of the electrical nerves 

 of the torpedo has no other effect than that of producing the 

 discharge. 



Proper Current of the Frog. Lastly, I must mention to 

 you another phenomenon of animal electricity which has 

 hitherto offered, by its speciality, some analogy to those we 

 have observed in the electric fishes. I refer now to the 

 current proper to the frog. 



Galvani discovered, and all philosophers after him have 

 observed, that a frog, prepared according to his usual me- 

 thod, contracts when we bring the lumbar nerves in contact 

 with the muscles of the thigh or leg. Nobili was the first 

 to study this phenomenon by the aid of the galvanometer. 

 Here is his fundamental experiment : a frog prepared in 

 the usual manner is placed between two small glasses 

 containing distilled water, in such a manner that on one side 

 the lumbar nerves, on the other, the legs, are immersed in 

 the liquid. Matters being thus arranged, the circuit is 

 closed by plunging into the two glasses the two platinum 

 extremities of a galvanometer. Observe the needle ; it 

 deviates, and from where it was, it reaches 5, 10, 

 and even 15. You see that the direction of deviation in- 

 dicates a current circulating in the frog from the legs to the 

 nerve; that is to say, from the legs to the upper part of the 

 animal. 



The signs of the current are augmented in intensity if, 

 in place of using a single frog, I form a pile with a number 

 of them. 



This arrangement is very easily understood : I employ 

 the varnished tray before spoken of, when treating of the 

 muscular current. I place on it some frogs, prepared in 



