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. Gay-Lussac made the important observation that when an insulated
person touches the torpedo with one finger, it is indispensible that
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
conducting or non-conducting body is interposed between the finger and
the electrical organ of the torpedo. This circumstance proves a great
difference between the torpedo and the gymnotus, the latter giving his
strokes through an iron 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 of the
organs, the hand that supports the plate never feels any shock, though
another insulated person may excite the animal, and the convulsive
movement of the pectoral fins may denote the strongest and most
reiterated discharges.
If, on the contrary, a person support the torpedo placed upon a
metallic plate, with the left hand, as in the foregoing experiment,
and the same person touch the superior surface of the electrical organ
with the right hand, a strong shock is then felt in both arms.
