334 ELECTEO-PHYSIOLOGY. 



sand and covered with a thin stratum of it, when the small fishes pass over it 

 unawares it launches its discharge upon them. 



In order to study the discharge of the torpedo, and observe those points of its 

 body in which the electric organ resides, it must be withdrawn from the water 

 and wiped dry ; prepared frogs should then be distributed on its surface. We 

 shall see the frogs, especially if the fish be irritated, fall into contractions ; and 

 if the torpedo be allowed to weary itself, we shall observe that the contractions 

 continue to retreat towards those parts of the body which correspond to the 

 electric organs. As long as it continues alive it responds, if sharply irritated 

 in any part of its body, with an electric discharge, and an experiment may be 

 made to show that the electric function is put in play at the will of the animal. 

 In effect, when the torpedo is irritated at any point of the tail or spine the dis- 

 charge occurs, provided the point irritated and the brain are connected by means 

 of the nerves of the spinal medulla. But if this medulla be divided, it will be 

 seen that the discharge is no longer provoked by irritation applied below the 

 point of division, though it still results from irritation above it. 



The early observer, Walsh, and also Gay Lussac, thought that the shock 

 might be elicited without forming an arc, that is, without touching at the same 

 time the belly and back of the torpedo. If the fish be not well isolated from 

 the ground, it is conceded that the shock will be experienced on touching one 

 face only of its body, because the arc is in that case established by the ground 

 and the entire person of the observer ; and hence, when fishermen perceive that 

 there are torpedoes among the fishes drawn in nets from the water, they are ac- 

 customed to throw buckets of water on them, in order thus to exhaust the shock. 

 It is easy, however, to show by decisive experiment the necessity of forming 

 the arc if we would have the shock. Let a living torpedo be wiped dry and 

 placed upon a tablet well isolated, with feet of gutta-percha. Alter several 

 galvanoscopic frogs have been spread over its body, let the organ be touched 

 Avith the end of the nerve of a galvanoscopic frog supported by tlie usual isola- 

 ting handle. At every discharge, whether spontaneous or provoked, given by the 

 torpedo, all the frogs undergo contraction except that supported on the isolating 

 handle. It is unnecessary to add, that if the tablet on which the torpedo is 

 placed were perfectly isolated, a condition difficult to realize, it would not be 

 necessary to support the galvanoscopic frog with such a handle. But it must 

 be further observed that even the isolated galvanoscopic frog will contract when 

 the torpedo gives the shock, if a portion of the nerve sufficiently long be 

 stretched upon the organ. We shall presently see the explanation of this fact. 

 After what has been said, there will be no difficulty in comprehending how 

 all the effects of the instantaneous electric discharge should be obtained from 

 that of the toi-pedo, namely, the spark, the deviation of the galvanometer, the 

 magnetization, the heating of the platina wire, the chemical effects. All these 

 phenomena, which I made the subject of attentive study in 1837, were at that 

 time an occasion of surprise; for it could not but be deemed strange that 

 electrical eff'ects so distinct should be realized from a fish, and these discoveries 

 offered, moreover, a new field for the study of animal electricity. Nor should I 

 omit to mention, as something surprising in its way, that only a few years 

 earlier experimenters of much ability, and even so illustrious a cultivator of 

 our science as Sir Humphrey Davy, had published that the discharge of the 

 torpedo did not produce a deviation in the needle of the galvanometer. In 

 order to obtfjin with facilit}^ the electrical effects in question, I use a single and 

 very simple apparatus, which consists of two circular plates of copper, of which 

 the lower has three feet of gutta-percha, that it may be isolated from the ground, 

 and the upper one is provided with an isolating handle. To each of these 

 plates is soldered or screwed a long copper wire. I take a living torpedo, dry 

 it properly, place it on the lower plate, and cover it with the upper one. It is 



