. PHENOMENA OF THE SHOCK. 195 



of these organs, that the signs of the current are percepti- 

 ble, but less evidently so than when the circuit has been 

 established between the two opposite surfaces. In order to 

 produce the deviation of the needle, by touching with the 

 galvanometer wires two points belonging to the same sur- 

 face of the fish, it is indispensable that one of the wires 

 should be in contact with a part near the periphery of the 

 electric organ, and that the other should occupy a point 

 almost diametrically opposite to that of the first. We then 

 have signs of the current which always passes in the gal- 

 vanometer, from the wire nearest to the median line of the 

 animal to that which is the most distant from it: we also 

 obtain them with the galvanometer, by keeping one of the 

 wires in contact with the abdominal or dorsal surface of one 

 of these organs, and by introducing the other into the inte- 

 rior of the organ itself. The current is invariably directed 

 from the wire which touches the dorsal surface, or that 

 which is nearest to it, to the other wire. These facts ex- 

 plain the feeble shock experienced by touching with the 

 finger the insulated torpedo. 



If, instead of the conductor of the galvanometer, we use 

 a metallic wire, one portion of which is bent into a spiral, 

 with an [unmagnetised] steel needle introduced within it, 

 and then touch the two surfaces of the torpedo with the ex- 

 tremities of the wire, the discharge magnetises the needle. 

 The direction of the magnetism produced by the discharge 

 of the fish is constant; that is to say, it is the same as that 

 indicated by the galvanometer, whatever may be the thick- 

 ness of the wire of the spiral, the length of the circuit, the 

 diameter of the spiral itself, and the length, thickness, or 

 temper of the steel needle. 



If we insulate the torpedo, placing on each of its surfaces 

 a disc of platinum, upon each of which has been placed a 

 piece of paper of. the same size> moistened with a solution 



