126 
THE SHOCJf A VITAL ACTION. 
they become more sensible if tbe animal be raised above the 
surface. I have often observed the same phenomenon in 
experimenting on frogs. 
The torpedo moves the pectoral fins convulsively every 
time it emits a stroke; and this stroke is more or less 
painful, according as the immediate contact takes place 
by a greater or less surface. We observed that the 
gymnotus gives the strongest shocks without making any 
movement with the eyes, head, or fins.* Is this difference 
caused by the position of the electric organ, which is not 
double in the gymnoti ? or does the movement of the 
pectoral fins of the torpedo directly prove that the fislj 
restores the electrical equilibrium by its own skin, dis- 
charges itself by its own body, and that we generally feel 
only the effect of a lateral shock ? 
We cannot discharge at will either a torpedo or a gym- 
notus, as we discharge at will a Leyden jar or a Voltaic 
battery. A shock is not always felt, even on touching the 
electric fish with both hands. We must irritate it to make 
it give the shock. This action in the torpedos, as well as in 
the gymnoti, is a vital action ; it depends on the will only 
of the animal, which perhaps does not always keep its elec- 
tric organs charged, or does not always employ the action 
of its nerves to establish the chain between the positive and 
negative poles. It is certain that the torpedo gives a long 
series of shocks with astonishing celerity ; whether it is that 
the plates or lamiutc of its organs arc not wholly exhausted, 
or that the fish recharges them instantaneously. 
The electric stroke is felt, when the animal is disposed to 
give it, whether we touch with a single finger only one of 
the surfaces of the organs, or apply both hands to the two 
surfaces, the superior and inferior, at once. In either case 
it is altogether indifferent whether the person who touches 
the fish with one finger or both hands be insulated or not. 
All that has been said on the necessity of a communication 
with the damp ground to establish a circuit, is founded on 
inaccurate observations. 
M. G-ay-Lussnc made the important observation that 
when an insulated person touches the torpedo with one 
* The anal fin of the gymnoti only has a sensible motion when these 
fishes are excited under the belly, where the electric organ is placed . 
