im 



ischiatie nerve, it is necessary, in order to pro- 

 duce contractions, to bring the other extremity of 

 the conducting* arc nearer and nearer to the 

 muscles, in proportion as the irritability of the 

 organs diminishes. Toward the end of the expe- 

 riment, the slightest stratum of water prevents 

 the passage of the electrical current, and it is 

 only by the immediate contact of the arc with 

 the muscles, that the contractions take place. I 

 dwell on these effects, dependant on three vari- 

 able circumstances ; the energy of the electro- 

 motive apparatus, the conductibility of the 

 medium, and the irritability of the organs that 

 receive the impressions ; as it is because experi- 

 ments have not been sufficiently multiplied with 

 a view to these three variable elements, that, in 

 the action of electrical eels and torpedoes, the 

 accidental circumstances have been taken for 

 absolute conditions, without which the electric 

 shocks are not felt. \ 



In wounded gymnoti, which give feeble but 

 very equal shocks, these shocks appeared to us 

 constantly stronger on touching the body of 

 the fish with a hand armed with metal, than 

 with the naked hand. They are stronger also, 

 when, instead of touching the fish with one hand, 

 naked, or armed with metal, we press it at 

 once with both hands, either naked or armed. 

 These differences, I repeat, become sensible 

 only when you have gymnoti enough at your 



