Digitale Ausgabe

The curious theory with which Volta has enriched theſcience of natural philoſophy, on the ſubject of electric fiſhhaving been received as authentic by many naturaliſts, rendersthe phenomenon of the Torpedo worthy of farther inveſtiga-tion. You know, my dear friend, what was our impatienceto procure theſe fiſh, and will perhaps be ſurpriſed that ſomuch time ſhould elapſe without having heard from us on the

---

* Annales de Chimie, Vol. LVI.|181| ſubject. At Genoa, we perceived ſome; but we were thenThe torpedofound at Genoaand Naples, butnot at CivitaVecchia. without our inſtruments. At Civita Vecchia we ſought themin vain. But during our ſtay at Naples we frequently pro-cured ſome very large and lively ones. In this letter you willfind detailed the experiments made by M. Gay-Luſſac andmyſelf on the powers of this fiſh (Raja-torpeda of Linneus).M. de Buch, a German mineralogiſt, well acquainted with allthe branches of phyſical ſcience, was witneſs to our proceed-ings. I ſend you the reſults, giving ſimple facts, unmixedwith theoretical ſpeculations. Our experiments were chieflydirected towards the diſcovery of that ſtate of the torpedowhen it was leaſt capable of exerting its power upon the hu-man frame. This power has been generally deſcribed asThe ſhock ofthe torpedo feelsdifferent fromthat of electri-city. electrical; but the ſenſation produced by it is materially differ-ent from that cauſed by the diſcharge of a Leyden phial.—Having no other book by us beſides the work wherein Aldini * combines the reſearches of Geoffroy with thoſe of Spallanzani and Galvani, it is not to be expected that we ſhould compareour experiments with thoſe which may have been previouſlymade by other philoſophers. 1. Though the ſtrength of the torpedo is far inferior to thatPowers of thetorpedo inferiorto thoſe of thegymnotus of S. America.Shock of thetorpedo moreviolent than thatof electricity.It acts underthe water, of the gymnotus, it is equally capable of cauſing painful ſen-ſations. A perſon much accuſtomed to electric ſhocks, canhardly ſuſtain that of a lively torpedo of four decimeters (16inches) in length. The animal acts under water, and it isonly when it loſes ſtrength that the fluid impedes its action. In this caſe, M. Gay Luſſac obſerved that the ſhock is notperceptible till the fiſh is raiſed above the ſurface. 2. I obſerved, when in South America, that the gymnotus—and ſeems touſe more effortthan the gym-notus. gives the moſt violent ſhocks, without any exterior movementof the eyes, the head, or the fins: it appeared as tranquil asa perſon when paſſing from one idea to another, or from oneſenſation to another. Not ſo the torpedo: We obſerved aconvulſive movement of the pectoral fins, each time it gave aſhock, which was more or leſs violent according as the ſurfacewas larger or ſmaller wherein the contact took place. 3. The powers of the torpedo and gymnotus cannot be ex-Shocks from thetorpedo andgymnotus can-not be obtainedbut by irritatingthe animal. cited at pleaſure, as we ſhould diſcharge a Leyden phial or a

---

* Memoires ſur la Torpille, dans l’Eſſai ſur le Galvaniſm,Vol. II. p. 61.|182| conductor. A ſhock is not always felt on touching an electricfiſh; it muſt be irritated before it will give the ſhock. Thisaction depends on the will of the animal, whoſe electric powersperhaps, are not kept conſtantly charged; yet it can recoverthem with wonderful celerity, as it is capable of giving a longſucceſſion of ſhocks. The ſhock ob-tained by a meretouch with thefinger, 4. The ſhock is felt (the animal being diſpoſed to give it)as well on touching with one finger a ſingle ſurface of theelectric organs, as on applying the two hands to the two ſur-faces, the upper and under, at once. In both caſes it is im-material whether the perſon applying his finger or his twohands, be inſulated or not. —but the con-tact muſt bedirect.Metals ſeem tobe non-conduc-tors of theſhock of thetorpedo. 5. When an iſolated perſon touches the torpedo with a ſinglefinger, it is indiſpenſible that the contact be immediate, as noſhock will be felt if a conducting body (of metal for example)be interpoſed between the finger and the organ of the fiſh.—For this reaſon, the animal may be touched with impunity bymeans of a key, or any other inſtrument of metal. 6. M. Gay-Luſſac having made this important obſervation,we placed a torpedo on a metal diſh, with which the inferiorſurface of its organs were in contact. The hand which ſup-ported this diſh experienced no ſhock, whilſt another iſolatedperſon irritated the animal, whoſe convulſive movement of thepectoral fins indicated a moſt violent emiſſion of the electricfluid. Experimentswhich ſhew thatthey conduct. 7. When on the contrary, a perſon held the torpedo in ametal diſh in his left hand (as in the preceding experiment),and with his right touched the ſuperior ſurface of the electricorgan, he experienced a ſmart ſhock in both arms at the ſamemoment. 8. The ſame was felt, on placing the fiſh between two metalplates, whoſe edges were not in contact with each other, andapplying the two hands at once above and below them. 9. But if the edges of the metal plates be ſuffered to toucheach other, no ſhock will be felt in either arm. The commu-nication between the two ſurfaces of the organs is, in this caſe,formed by the plates; and the new connection ariſing fromthe contact of the two hands with the plates is without effect. The organs ofthe torpedo haveno influence onthe electrome-ter. 10. The moſt ſenſible electrometer manifeſted no electricaltenſion in the organs of the torpedo; in whatever way it wasapplied, it was not in the leaſt affected; neither, on directing |183| it towards the organs, nor in inſulating the fiſh, covering itwith a metallic plate, and making a communication betweenthis plate, by means of a conducting thread, and the condenferof Volta, was there any indication (as with the gymnotus)that the animal affected the electric intenſity of ſurroundingbodies. 11. As electric fiſh, when healthy, exerciſe their powers asExamination ofthe conductingpowers of water. forcibly beneath the water as in the open air, we were led toexamine the conducting properties of this fluid. Several per-ſons formed a chain of hands between the ſuperior and inferiorſurfaces of the organs of the torpedo: the ſhock was not feltuntil they had wetted their hands. The action was not inter-cepted when two perſons ſupported the torpedo with theirright hands; and inſtead of holding each other’s left hand,they each plunged a metallic rod into water placed upon aniſolated body. 12. By ſubſtituting flame in lieu of water, the communica-Flame does notconduct theſhock. tion was deſtroyed, until the rods touched each other in theflame. 13. It muſt, however, be obſerved, that in water, as inNo ſhock can beobtained withoutimmediate con-tact with thefiſh. air, the ſhock was not perceptible without an immediate con-tact with the body of the electric fiſh: the leaſt poſſible inter-vention of the water prevented it. This fact is the more re-markable, as it is known that in galvanic experiments, wherethe frog is immerſed in water, it is ſufficient to direct the ſilverforceps towards the muſcles to cauſe a contraction, though abody of water be interpoſed, equal to one or two millimetresin thickneſs, or about one-twentieth of an inch. Theſe, my dear friend, are the principal obſervations whichOrgans of thetorpedo not ſuſ-ceptible of anyexceſs of charge. we have made on the torpedo. The experiments, No. 4 and10, prove that the electric organs of theſe animals are not ſuſ-ceptible of any intenſity or exceſs of charge. Their actionmay rather be compared to that of a combination of Leydenphials, than to the conductor of Volta. Without communica-tion no ſhock could be felt: and having experienced the powerDoubt whetherthe ſhock of thegymnotus can befelt without ac-tual contactwith it.Torpedo ſup-poſed to act byan electric equi-librium, the op-poſite ſtate beingvery near. of the gymnotus through very dry cords, I imagine, that whereI have been affected by this powerful animal without directcontact, it had been occaſioned by ſome deficiency in my in-ſulated ſtate. If the torpedo act by poles, that is by an elec-tric equilibrium which poſſeſſes a tendency to repleniſh itſelf,experiments 5 and 6 ſeem to prove that theſe poles exiſt near |184| each other, on the ſame ſurface of the organ. The ſhock isfelt on merely touching the ſurface with the finger. A plateinterpoſed between the hand and the organ, (Exp. 6,) re-eſta-bliſhes the equilibrium, and the hand which ſuſtains the plateis not affected, becauſe it is placed beyond the current. But Objections tothis notion.if we ſuppoſe an heterogeneous number of poles upon eachſurface of the organ, whence does it ariſe, that, in coveringtheſe ſurfaces with two metal plates, whoſe edges do not toucheach other, and placing the hands on theſe plates, the equili-brium ſhould be found in the arms? Why, it may be aſked,does not the poſitive electricity of the inferior ſurface ſeekat the moment of exploſion the negative electricity of the nextor neareſt pole, but rather ſeek it in the ſuperior ſurface of theelectric organ? Perhaps theſe difficulties may not be inſur-mountable; yet the theory of theſe vital actions well deſerves Conſiderationsof theory.attentive reſearch. Geoffroy has proved that thornbacks, whogive no ſigns of electricity, are furniſhed with organs analo-gous to thoſe of the torpedo. The leaſt injury on the brain ofthe torpedo deſtroys its electric powers. The nerves are nodoubt concerned chiefly in theſe phenomena; and the phyſio-logiſt who ſhould admit the power of vital actions, might withſucceſs oppoſe the theory of the naturaliſt, who would endea-vour to explain all by the contact of the albumino-gelatinouspulp of the nervous laminæ wherewith nature has endowedthe organs of the torpedo.