474 



The electricity of the 

 great care in the year ! *( 

 Lusoac, who priHtir 

 The following are t 

 tained by these di.< 



E L E C T R I C I T V. 



torpedo was examined with 

 ~rs HuinlMildt and 

 )d several torpedo* at Naples. 

 ' result* which were ob- 

 pliiloMiphera. 



1. A person much in the habit of receiving electric 

 alrocks, can support with some difficulty the shock of a 

 vigorous torpedo 1 4 inches long. The action of the 

 torpedo below water is not perceptible, till it is raised 

 above the surface of the water. 



2. Before each shock, the torpedo move* its pectoral 

 fins in a convulsive manner, mid the violence of the 

 shock is always proportional to the extent of the surface 

 of contact. 



3. The organs of the torpedo cannot be discharged 

 by us at our pleasure, nor does it always communicate 

 a shock when touched. It must be irritated before it 

 gives the shock, and, in nil probability, it does not keep 

 its electric organs charged. It charges them, how e\ . r. 

 with astonishing quickness, and is thence capable of 

 giving a long series of shocks. 



4. The shock is experienced, when a single finger is 

 applied to a single surface of the electric organs, or when 

 the two hands are placed one on the upper and one on 

 the under surface nt the same time, and in both these 

 cases the shock is equally communicated, whether the 

 person is insulated or not. 



5. If an insulated person touches the torpedo with 

 his finger, it must be in immediate contact, as no shock 

 is received if the aiyjnal is touched with a key, or any 

 other conductinjptiody. 



G. When the torpedo was placed upon a metallic plate, 

 so that the inferior surface of its electric organ touched 

 the metal, the hand which supported the plate felt no 

 shock, although the animal wag irritated by another in- 

 sulated person, and when it was obvious, from thecon- 

 %'iilsive motions of its pectoral fins, that it was in a state 

 of powerful action. 



7. If a person, on the contrary, support with his left 

 hand the torpedo placed on a metallic plate, and if he 

 touches with his right hand the upper surface of the 

 electric organ,a violent commotion will be felt in both his 

 arms at the same instant. 



8. A similar shock will be received, if the fish is pla- 

 ced between two metallic plates, the edges of which do 

 not touch, and if a person applies a hand to each plate 

 at the same instant. 



9. If, under the circumstances of the preceding ex- 

 periments, there is a connection between the edges of the 

 two plates, no shock will be experienced, as a commu- 

 nication is now formed between the two surfaces of 

 the organ. 



10. The organs of the torpedo do not affect the most 

 delicate electrometer. Every method was tried in vain 

 of communicating electricity to the condenser of Volta. 



1 1. A circle of connection being formed, by a num- 

 ber of persons, between the upper and under surfaces of 

 the organs, they received no shock till their hands were 

 moistened in water. The shock was equally felt, when 

 two persons, who had their right hand applied to the 

 torpedo, instead of taking hold of each other's left 

 hands, plunged a pointed piece of metal into a drop of 

 water placed upon an insulating body. 



12. By substituting flame in place of a drop of wa- 

 ter, no sensation was experienced till the two pointed 

 pieces of metal came in contact with the flame. 



13. No shock will be experienced, either in air or 

 below water, unless the body of the electric fish is im- 

 mediately touched. The torpedo is unable to commu- 



nicate its shock through a layer of water, however 

 thin. 



I *. The least injury done to the brain of this animal 

 prevent* its electrical action. 



A number of curious experiments on the torpedo were 

 made by the Ablx- Spallanzani. He observed, that when 

 the animal was laid upon a plate of glass, the shock was 

 then the strongest " In irritating the back of the torpe- 

 do," he remarks, " I always ( obtaincd the shock whether 

 it was out of the water or in it. If, instead of irritating 

 the back, I gently irritated the breast, I also received a 

 shock, but not so frequently as in irritating the back. 

 If I irritated the back with one hand, and the breast 

 with another, the hand which touched the back re- 

 ceived the shock but not the other. But when I irri- 

 tated the back with two fingers of one hand, and the 

 breast with four fingers of the other, then I received 

 the shock from the breast, and obtained all these re- 

 sults whether I was insulated or not." M. Spallanzani 

 observed, that some minutes before the torpedo ex- 

 pired, the shocks were not given at intervals, as in the 

 healthy state of the animal, but were changed into a 

 continual battery of small shocks ; and he compares the 

 sensation to that which would be produced by laying the 

 fingers upon a heart in a state of pulsation. The bat- 

 tery continued seven minutes, and during this short space 

 of time his fingers experienced 3 16 shocks ; the shocks 

 then suffered.an interruption, and the animal, imme- 

 diately before it died, gave a few very languid shocks. 

 We are indebted to Spallanzani for the knowledge of a 

 still more curious fact. He found, that even the foe- 

 tuses of a toq>edo, when in the womb of the mother, 

 possess the same electrical property as after they are 

 born. Having dissected a female torpedo, when she 

 was about to expire, he saw in the ovarium eggs al- 

 most round and of different magnitudes, and on open- 

 ing two vessels which abutted against the rectum, he 

 found two perfectly formed foetuses, which he detached 

 from their envelopes, and submitted to the same ex- 

 periments which he had made upon the mother. These 

 foetuses gave a perceptible shock, which was strongest 

 when they were laid upon a plate of glass. 



The common experiments on the torpedo were re- 

 peated and verified at Narbonne in the month of August 

 1779, by the Abbe Bertholon. 



At the request of Mr Walsh, the celebrated anato- 

 mist Dr Hunter examined carefully the electrical or- 

 gans of a torpedo about 18 inches long and 15 broad, 

 and about two inches thick in its thickest part. The 

 following were the results of his examination. 



" The electric organs of the torpedo are placed on 

 each side of the cranium and gills, reaching from thence 

 to the semicircular cartilages of each great fin, and ex- 

 tending longitudinally from the anterior extremity of 

 the animal, to the transverse cartilage which divides 

 the thorax from the abdomen ; and within these limits 

 they occupy the whole space between the skin of the 

 upper and under surfaces ; they are thickest at the 

 edges near the centre of the fish, and become gra- 

 dually thinner towards the extremities. Each electric- 

 organ, at its inner longitudinal edge, is unequally hol- 

 lowed, being exactly fitted to the irregular projection 

 of the cranium and gills. The outer longitudinal Mge 

 is a convex elliptic curve. The anterior extremity of 

 each organ makes the section of a small circle ; and 

 the posterior extremity makes nearly a right angle with 

 the inner edge. Each organ is attached to the sur- 

 rounding parts by a close cellular membrane, and also 

 by short and strong tendinous fibres, which pass di- 



Dweriptirt 

 Klectnriif. 



Experi- 

 ment* of 

 Spatlan- 

 zui. 



Hunter', 

 observations 

 on the 

 electrical 

 organs of 

 tilt tnrpcd*. 



