EFFECTS OT TABULATORS. 127 



linger, 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 con- 

 ducting or non-conducting body is interposed between the 

 finger and the electrical organ of the torpedo. This cir- 

 cumstance 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. The sensation is the same when 

 the fish is placed between two metallic plates, the edges of 

 which do not touch, and the person applies both hands at 

 once to these plates. The interposition of one metallic 

 plate prevents the communication if that plate be touched 

 with one hand only, while the interposition of two metallic 

 plates does not prevent the shock when both hands are 

 applied. In the latter case it cannot be doubted that the 

 circulation of the fluid is established by the two arms. 



If, in this situation of the fish between two plates, there 

 exist any immediate communication between the edges of 

 these two plates, no shock takes place. The chain between 

 the two surfaces of the electric organ is then formed by 

 the plates, and the new communication, established by the 

 contact of the two hands with the two plates, remains with- 

 out effect. \Ve carried the torpedo with impunity between 

 two plates of metal, and felt the strokes it gave only at the 

 instant who- they ceased to touch each other at the 



Nothin-r in the torpedo or in the gymnotus indicates that 

 the animal modifies the electrical state of the bodies by 

 tthirh it is surrounded. The most delicate electrometer is 

 no way affected in whatever manner it is employed, whether 



