ELECTEO-PHYSIOLOGY. 666 



the electrical species best known, and Avhicli have been the subject of extensive 

 researches. These are the silurus of the Nile, the gymnotus of South America, 

 and the torpedo, which is frequently met with in the ocean and in our own seas. 



From the times of Aristotle and Pliny notice has been taken of the property 

 possessed by the living torpedo of communicating a shock to those by whom it 

 is touched, and thus benumbing the member which comes into contact with it ; 

 hence the names of inrpedo, tremolo, mago, given to these fish iu different coun- 

 tries. Our own Eedi was the first to discover that what he called the stiipefij- 

 ing or dolorijic property of the torpedo has its seat in two special organs to 

 which he gave the name o^ falcated organs, and which are now termed electric 

 organs. In the torpedo, stripped of its skm, we find that on each side of the 

 head there exist two flattened elliptical masses which are connected with the 

 animal by integuments and ligaments, and by some large nerves which are rami- 

 fied in the electric organ. Alter Redi the most complete study of the electric 

 function of the torpedo and gymnotus is due to Walsh, who, in 1773, published 

 in the Philosophical Transactions a series of experiments which, as far as was 

 then practicable, demonstrated, through the employment of arcs now isolating 

 and now conducting, that these fish owe the property in question to an organ 

 which t>uddenly develops a great quantity of electricity, and that the two op-' 

 posite faces of this organ are the two poles, the two extremities of this animal 

 battery. 



These notices being premised, I shall describe the electrical properties of the 

 torpedo with the simplicity and in the order with which we should study any 

 physical apparatus. To receive the electric shock of the fish it is necessary, if 

 the animal is in water, to touch, or rather press, with the hands the electric 

 organs. If it be the torpedo, one hand is applied on the back and the other on 

 the belly ; if the gymnotus, it is necessary to grasp Avith one hand the head, 

 and with the other the tail. While these fishes are yet vivacious, having been 

 just caught, the shocks are very strong, and out of the water even stronger than 

 in it, because, as is readily understood, while the animal is still immersed a 

 great part of the electricity passes into the liquid and not into the body of the 

 expeiimenter. When just removed from their element, these fishes, perhaps 

 through irritation or uneasiness, give rapidly a succession of shocks which, when 

 the animal is vigorous, do not differ from those of a good electro-magnetic ma- 

 chine. Out of the water, however, the fish soon becomes wearied, and yields 

 weaker and more intermittent shocks ; naturally, because it is enfeebled, but in 

 part, perhaps, because of an instinct which warns it that in the air the shocks 

 may be partially expended on itself. It often occurs that, in irritating a tor- 

 pedo out of water with arcs formed of isolating material, the animal gives no 

 shocks, or but feAv, which is not the case when conducting arcs are used. The 

 electrical function of these fishes is for them, evidently, a Aveapon of offence or 

 defence ; if irritated, especially in the neighborhood of the organs, they give a 

 shock, as they do also in order to benumb the small fishes which serve them for 

 food. The well-known description which Ilumboldt gives us of the fishery of 

 the gymnotus in the lakes of Brazil, proves the vigor with which these fishes 

 exert their electric faculty in combating their enemies. The natives use horses 

 in this pursuit, Avhich, being driven into the lakes, often fall victims to the elec- 

 tric discharges of the gymuoti. In the mean time many of the latter, ex- 

 hausted in the contest, approach the shore half alive, and are drawn out with 

 hooks. 



When the gymnotus avails itself of the electric organ to kill the fishes it 

 would devour, it goes to work like a physicist.: as the poles of its organ are at 

 the extremities of its body, it bends itself into a bow and seeks to bring those 

 extremities into the closest proximity with the victim. The torpedo, being flat- 

 tened in form and having the poles of its organ iu contact with the belly and 

 spine, cannot use this artifice ; but it employs another : lying generally in the 



