DR. DAVY ON THE TORPEDO. 647 



ing, with the finger or hand, one surface only of the fish *. The experiments which 

 I have made expressly on this point have led me to a different conclusion, namely, 

 that it is requisite to touch the opposite surfaces of the electrical organs or organ, 

 or a conductor or conductors connected with them, to receive a shock. In very 

 many instances that I have irritated Torpedos by pressing with the finger on different 

 parts of the back, as the upper surface of the electrical organs, and on the margin of 

 the pectoral fins, however much the fish were irritated, I never had any sensation 

 excited by the electricity, which there vvas reason to believe was discharged ; though 

 immediately after, on touching the two surfaces, irritating only the upper, shocks 

 were received. On some few occasions, I have perceived a shock, when apparently 

 only one surface of the fish was touched ; but I believe in these instances the dis- 

 charge took place through the water -f-. In corroboration, I may mention, that in 

 experiments in which one surface only has been touched and irritated, the fish them- 

 selves appear to make an effort to bring, by muscular contraction, the border of the 

 under surface (the upper being pressed on) in contact with the offending body. And 

 this I have witnessed as distinctly in the foetal fish as in the adult ; clearly showing 

 that the effort is instinctive J. 



The conductor, which I suppose to be necessary for conveying the electricity when 

 a shock is felt without immediate contact, exists in salt water. The galvanometer 

 has been affected when the two extremities of it have been brought in contact, one 

 with the back of the fish, and the other with the water, two or three inches from the 

 fish. And in one instance I experienced a shock, although I touched the water alone, 

 close to a Torpedo ; it was in removing an active fish, by means of an earthenware 

 dish, from one vessel into another : the hand that received the shock grasped the 

 wet margin of the dish just as the Torpedo entered it. 



I believe that the Torpedo has the power of discharging its electricity in any direc- 

 tion it chooses. This inference is drawn from finding that when one hand, in contact 

 with the opposite surfaces of the fish, is receiving shocks, the other hand, immersed 

 in the water close by, has received no shock. And, in confirmation of this, I may 

 mention, (and at the same time to show how the discharge is connected with the 

 volition of the animal,) that when I have applied to the opposite surfaces of a Tor- 

 pedo copper plates, merely gently touching, joined together by a copper wire, and 



* Annales de Chimie et de Physique, torn. xi. p. 430. 



t The most remarkable example of the kind of which I have any note, was that of a young Torpedo, which 

 gave slight shocks to the hand on which it was supported, whether just under the surface of the water, or just 

 after it was taken out of the water into the air. 



{ In my former paper, I have supposed that the mucus with which the Torpedo is lubricated may be a con- 

 ducting medium between the two opposite surfaces. This was an erroneous view ; it may serve that purpose 

 to the surfaces individually. Seeing the error theoretically, I was led to examine the margins of the fins, and 

 they have appeared to me to have less mucus adhering to them than any other part of the fish, as if intended 

 partially to insulate the electrical organs. 



