EFFteCTS OF TTJSELATOBS. 127 
finger, it is indispensible tliat the contact be direct. The 
fish may with impunity be touched with a key, or any 
other metallic instrument; no shock is felt when a con- 
ducting or non-conducting body is interposed between the 
huger and the electrical organ of the torpedo. This cir- 
cumstance proves a great difference between the torpedo 
und the gymuotus, the latter giving his strokes through an 
U'On rod several feet long. 
When the torpedo is placed on a metallic plate of very 
little thickness, so that the plate touches the inferior surface 
°f the organs, the hand that supports the plate never feels 
an 7 shock, though another insulated person may excite the 
a Uvtnal, and the convulsive movement of the pectoral fins 
111 a y denote the strongest and most reiterated discharges. 
ifi on the contrary, a person support the torpedo placed 
u pon a metallic plate, with the left hand, as in the foregoing 
experiment, and the same person touch the superior surface 
?f the electrical organ with the right hand, a strong shock 
la then felt in both arms. The sensation is the same when 
the f ls h i s placed between two metallic plates, the edges of 
^nich do not touch, and the person applies both hauds at 
°Uee to these plates. The interposition of one metallic 
Plate prevents the communication if that plate be touched 
"Wi one hand only, while the interposition of two metallic 
plates does not prevent the shock when both hands are 
a Pplied. In the latter case it cannot be doubted that the 
Peculation of the fluid is established by the two arms. 
If, in this situation of the fish between two plates, there 
®xist any immediate communication bctweeu the edges of 
iese two plates, no shock takes place. The chain between 
!j e Wo surfaces of the electric organ is then formed by 
( / le plates, and the new communication, established by the 
( -°utact of the two hands with the two plates, remains with- 
ut effect. We carried the torpedo with impunity between 
plates of metal, and felt the strokes it gave only at the 
^tant whp’ they ceased to touch each other at tho 
Nothing in the torpedo or in the gymnotus indicates that 
W' a”. 111 : 11 modifies the electrical state of the bodies by 
tic) 1 ^ * s surr °undcd. The most delicate electrometer is 
^ a y affected in whatever manner it is employed, whether 
