GYMNOTUS, in ichthyology, a genus of fishes belonging to the order of apodes. They have two tentacula at the upper lip; the eyes are covered with the common skin; there are five rays in the membrane of the gills; the body is compressed, and carinated on the belly with a fin. There are five species; the most remarkable of which is the electricus. This species is peculiar to Surinam; and is found in the rocky parts of the river, at a great distance from the sea. The most accurate description we have of this fish is in the Phil. Trans. for 1775, where Alex. Garden, M. D. gives an account of three of them brought to Charlestown in South-Carolina. The largest was about three feet eight inches in length, and might have been from 10 to 14 inches in circumference about the thickest part of its body. The head was large, broad, flat, and smooth; impressed here and there with holes, as if perforated with a blunt needle, especially towards the sides, where they were more regularly ranged in a line on each side. There were two nostrils on each side; the first large, tubular, and elevated above the surface; the others small, and level with the skin. The eyes were small, flattish, and of a bluish colour, placed about three quarters of an inch behind the nostrils. The whole body, from about four inches below the head, was clearly distinguished into four longitudinal parts or divisions. The upper part or back was of a dark colour, and separated from the other parts on each side by the lateral lines. These lines took their rise at the base of the head, just above the pectoral fins, and run down the sides, gradually converging as the fish grew smaller to the tail. The second division was of a lighter and clearer colour than the first, inclining to blue. It seemed to swell out on each side; but towards the under part it is again contracted and sharpened into the third part or carina. This part is easily distinguished from the other two by its thinness, its apparent laxness, and by the reticulated skin of a more grey and light colour, with which it is covered. The carina begins about six or seven inches below the base of the head; and, gradually deepening or widening as it goes along, reaches down to the tail, where it is thinnest. The fourth part is a long, deep, soft and wavy fin, which takes its rise about three or
four inches at most below the head; and thus runs down the sharp edge of the carina to the extremity of the tail. The situation of the anus was very singular; being an inch more forward than the pectoral fins. Externally it seemed to be a pretty large rima; but the formed excretions were only the size of a quill of a common dunghill-fowl. There were two pectoral fins situated just behind the head, scarcely an inch in length; of a very thin, delicate consistence, and orbicular shape. They seemed to be chiefly useful in supporting and raising the head of the fish when he came up to breathe; which he was obliged to do every four or five minutes. Across the body were a number of small bands, annular divisions, or rather rugæ of the skin. By means of these the fish seemed to partake of the vermicular nature, had the power of lengthening or shortening its body like a worm, and could swim backwards as well as forwards, which is another property of the vermicular tribe. Every now and then it laid itself on one side in the water, as if to rest.
This fish hath the astonishing property of giving the electric shock to any person, or number of persons, either by the immediate touch with the hand, or by the mediation of any metallic conductor; and the person who kept them, told Dr. Garden, that they had this property much stronger when first caught than afterwards: "The person (says he) who is to receive the shock, must take the fish with both hands, at some considerable distance asunder, so as to form the communication, otherwise he will not receive it: at least I never saw any one shocked from taking hold of it with one hand only; though some have assured me, that they were shocked by laying one hand on it. I myself have taken hold of the largest with one hand often, without ever receiving a shock; but I never touched it with both hands, at a little distance asunder, without feeling a smart shock. I have often remarked, that when it is taken hold of with one hand, and the other is put into the water over its body, without touching it, the person received a smart shock; and I have observed the same effect follow, when a number joined hands, and the person at one extremity of the circle took hold of or touched the fish, and the person at the other extremity put his hand into the water, over the body of the fish. The shock was communicated through the whole circle, as smartly as if both the extreme persons had touched the fish. In this it seems to differ widely from the torpedo*, or else we * See Torpedo. are much misinformed of the manner in which the benumbing effect of that fish is communicated. The shock with our Surinam fish gives, seems to be wholly electrical; and all the phenomena or properties of it exactly resemble those of the electric aura of our atmosphere when collected, as far as they are discoverable from the several trials made on this fish. This stroke is communicated by the same conductors, and intercepted by the interposition of the same original electrics, or electrics per se as they used to be called. The keeper of this fish informs me, that he caught them in Surinam river, a great way up, beyond where the salt-water reaches; and that they are a fresh-water fish only. He says, that they are eaten, and by some people esteemed a great delicacy. They live on fish, worms, or any animal-food if it is cut small.
Gymnotus, small so that they can swallow it. When small fishes are thrown into the water, they first give them a shock, which kills or so stupifies them, that they can swallow them easily, and without any trouble. If one of these small fishes, after it is shocked, and to all appearance dead, be taken out of the vessel where the electrical fish is, and put into fresh water, it will soon revive again. If a larger fish than they can swallow be thrown into the water, at a time that they are hungry, they give him some smart shocks, till he is apparently dead, and then they try to swallow or suck him in; but, after several attempts, finding he is too large, they quit him. Upon the most careful inspection of such fish, I could never see any mark of teeth, or the least wound or scratch on them. When the electrical fish are hungry, they are pretty keen after their food; but they are soon satisfied, not being able to contain much at one time. An electrical fish of three feet and upwards in length cannot swallow a small fish above three or at most three inches and a half long. I am told, that some of these have been seen in Surinam river upwards of 22 feet long, whose stroke or shock proved instant death to any person that unluckily received it."
Several other accounts of this fish have been published by different persons, but none of them so full and distinct as the above. They all agree that the electric virtue of the fish is very strong. Mr. Fermin in his natural history of Surinam, published in 1765, tells us, that one cannot touch it with the hands, or even with a stick, without feeling a horrible numbness in the arms up to the shoulders; and he farther relates, that, making 14 persons grasp each other by the hands, while he grasped the hand of the last with one of his, and with the other touched the eel with a stick, the whole number felt so violent a shock, that he could not prevail on them to repeat the experiment. V. Vanderlott, in two letters from Rio Essequibo dated in 1761, makes two species, the black and the reddish; though he acknowledges, that, excepting the difference of colour and degree of strength, they are not materially different. In most experiments with these animals, he remarked a surprising resemblance between them and an electrical apparatus: nay, he observed, that the shock could be given to the finger of a person held at some distance from the bubble of air formed by the fish when he comes to the surface of the water to breathe; and he concluded, that at such times the electrical matter was discharged from its lungs. He mentions another characterizing circumstance, which is, that though metals in general were conductors of its electric property, yet some were found to be sensibly better than others for that purpose. Of this property Dr. Priestley takes notice, and says that a gold ring is preferable to any thing else. The same is likewise observed by Linnæus. Dr. Priestley adds, that the sensation is strongest when the fish is in motion, and is transmitted to a great distance; so that if persons in a ship happen to dip their fingers or feet in the sea, when the fish is swimming at the distance of 15 feet from them, they are affected by it. He also tells us, that the gymnotus itself, notwithstanding all its electric powers, is killed by the lobster.