TRANSMISSION ON THIS SHOCK. 
12S 
stratum of water between the gold and the muscles is more 
tl ian half a line thick. In the same manner, by employing 
a conducting arc composed of two pieces of zinc ana silver 
soldered together endways; and resting, as before, one of 
the extremities of the metallic circuit on -the femoral nerve, 
d is necessary, in order to produce contractions, to bring 
tee other extremity of the conductor nearer and nearer to 
the muscles, in proportion as the irritability of the organs 
diminishes. Toward the end of the experiment the slightest 
stratum of water prevents the passage of the electrical cur- 
rent, and it is only by the immediate contact of the are with 
the muscles, that the contractions take place. These effects 
are , however, dependent on three variable circumstances ; 
the energy of the electromotive apparatus, the conducti- 
vity of the medium, and the irritability of the organs which 
receive the impressions : it is because experiments have 
Hot been sufficiently multiplied with a view to these three 
'triable elements, that, in the action of electric eels and 
orpedos, accidental circumstances have been taken for 
' l osoiute conditions, without which the electric shocks are 
u °t felt. 
in wounded gymnoti, which give feeble but very equal 
* docks, these shocks appeared to us constantly stronger on 
'inching the body of the fish with a hand armed with metal, 
. han with the naked hand. They are stronger also, when, 
l natead of touching the fish with one hand, naked, or armed 
"ith metal, we press it at once with both hands, either 
u jked or armed. These differences become sensible only 
hen one lias gymnoti enough at disposal to be able to 
‘ loose the weakest ; and when the extreme equality of the 
®?tric discharges admits of distinguishing between the sen- 
; ;ai ons felt alternately by the band naked or armed with a 
e tal, by one or both hands naked, and by one or both 
dhiis armed with metal. It is also in the case only of 
■, dil shocks, feeble and uniform, that they are more sen- 
ior R ‘ ° Q k° ue hiiig the gymnotus with one hand (without 
? lu g a chain) with zinc, than with copper or iron. 
, nesnious substances, glass, very dry wood, horn, and even 
D „ ra ' s > which are generally believed to be good conductors, 
event the action of the gymnoti from being transmitted to 
a - I was surprised at not feeling the least shock on 
