The Gymnotus, or Electrical Eel.

Several species of fish, particularly the ray, are known to possess the power of giving, at will, electrical shocks, of greater or less intensity.— The Gymnotus, or Electrical Eel, that has this power in the highest degree, abounds in many of the rivers of tropical South America, especially in the Oroonoke, the Amazon and the rivers of Dutch Guiana, whence most of the specimens that have been seen in this country and Europe have been procured.

Humboldt, in the personal narrative of his travels in the Equinoctial regions of this continent during the years 1799 and 1804, gives a very minute account of experiments he made with electrical eels he obtained at Calabozo, a small town in the Llanos, or Plains of Venezula, that border the Oroonoko.

The basins of stagnant water in that vicinity were full of the eels, but the natives have so great a dread of their shocks that they were very reluctant to catch them, and as for catching them with nets, that was almost impossible, on account of the extreme agility of the fish, which bury themselves in the mud like serpents.

The travelers were unwilling to employ any intoxicating drugs, that are sometimes used in taking fish, as the eels would thereby be benumbed and lose much of their electrical power.

The Indians professed to believe that the eels could be handled with impunity by a person chewing tobacco, but their faith was not strong enough to induce them to subject it to a practical test.

The enterprising travelers were, however, determined to get some of the eels, and finally the Indians told them that they would “fish with horses.”

“We found it difficult,” says Humboldt, “to form an idea of this extraordinary manner of fishing; but we soon saw our guides return from the Savannah, which they had been scouring for wild horses and mules.”

About thirty of these animals were forced to enter the pool, and the scene that ensued is thus described:

“The extraordinary noise caused by the horses’ hoofs makes the fish issue from the mud, and excites them to combat.

These yellowish and livid eels, resembling large aquatic serpents, swim on the surface of the water, and crowd under the bellies of the horses and mules.

A contest between animals of so different an organization furnishes a very striking spectacle.

The Indians, provided with harpoons and long slender reeds, surrounded the pool closely, and soon climb upon the trees, the branches of which extend horizontally over the surface of the water.

By their wild cries, and the length of their reeds, they prevent the horses from running away, and reaching the bank of the pool.

The eels, stunned by the noise, defend themselves by the repeated discharge of their batteries.

During a long time they seem to prove victorious.

Several horses sink beneath the violence of the invisible strokes, which they receive from all sides in organs the most essential to life, and stunned by the force and frequency of the shocks, disappear under the water.— Others panting, with mane erect, and haggard eyes, expressing anguish, raise themselves, and endeavor to flee from the storm by which they are overtaken.

They are driven back by the Indians into the middle of the water but a small number succeed in eluding the active vigilence of the fishermen.

These regain the shore, stumbling at every step, and stretch themselves on the sand, exhausted with fatigue, and their limbs benumbed by the electric shocks of the Gymnoti.”

“In less than five minutes two horses were drowned.

The eel, being five feet long, and pressing itself against the belly of the horses; makes a discharge along the whole extent of its electric organ. It attacks at once the heart, the intestines, and the plexus cœliacus of the abdominal nerves.

It is natural, that the effect felt by the horses should be more powerful, than that produced upon man by the touch of the same fish at only one of his extremities.

The horses are probably not killed, but stunned.

They are drowned from the impossibility of rising amid the prolonged struggle between the other horses and the eels.”

“We had little doubt that the fishing would terminate by killing successively all the animals engaged, but by degrees the impetuosity of this unequal combat diminished, and the wearied Gymnoti dispersed.

They require a long rest, and abundant nourishment, to repair what they have lost of galvanic force.

The mules and horses appear less frightened, their manes are no longer bristled, and their eyes express less dread.

The Gymnoti approach timidly the edge of the marsh, where they are taken by means of small harpoons fastened to long cords.

In a few minutes we had five large eels, the greater part of which were but slightly wounded.”

The temperature of the water in which these eels live is about 80°.

Their electric force diminishes, it is said, in colder waters, though they will live in such.

They are the longest of the electrical fishes.

Some of those obtained at Calabozo measured five feet three inches in length, and were three inches and a half through.

Their skin is constantly covered with a mucous matter, which, as Volta has proved, conducts electricity twenty or thirty times better than pure water.— No electrical fish yet discovered has scales.

The Gymnoti are fond of breathing air on the surface of the water, but, unlike the common eels which often wander a part of the night on the grass, soon die if thrown upon the ground.

Their brain, electrical organs and muscles, are supplied with an extraordinary amount of arterial blood.

It is dangerous to expose one’s self to the first shocks of a very large and strongly irritated gymnotus.

Humboldt says he does not remember having ever received from the discharge of a large Leyden jar, a more dreadful shock, than he experienced by imprudently placing both his feet on a gymnotus just taken out of the water.

He was affected the rest of the day with a violent pain in the knees, and in almost every joint.

In Dutch Guiana electrical eels were formerly employed to cure the paralytic, as in old times, among the Greeks, the torpedo, with a much less electrical power, was used for the same purpose.

Gymnoti are neither charged conductors, nor batteries, nor electromotive apparatuses, the shock of which is received every time they are touched.

The electric action of the fish depends entirely on its will, sometimes suffering itself to be handled gently without giving any indication of its peculiar powers, and at others discharging its batteries on the least touch.

It has the power also of acting toward the point of greatest irritation.

For instance two persons may have hold of the same fish, and one by pressing too hard may receive a severe shock, while the other experiences no sensation.

A still more remarkable power it possesses is that of darting and directing its stroke against an object at some distance from it.

In this way it often kills small fish.

Although usually very prompt to resent any irritation by exerting its electrical powers, it will sometimes struggle violently with a person holding it by the tail without communicating any shock.

Humboldt made a slight incision in one, near the pectoral fin, and galvanized the wound by the contact of two pieces of zinc and silver.

The gymnotus bent itself convulsively, and raised its head out of water, as if affrighted by a sensation altogether new, but no vibration was felt in the hands which held the metals.

The gymnoti are called electrical eels, and probably with propriety, but the electrical power they possess differs some what from common electricity.

Resinous substances, very dry wood, horn, bones, &c., generally believed to be good conductors, prevent the action of the gymnoti from being transmitted to man.

When a chain is formed by several persons holding each others’ hands, and one of them touches the fish, the shock is sometimes felt by all simultaneously, while it sometimes happens that the shock, even when most severe, is felt alone by the person in immediate contact with the fish.

The belief is popularly entertained that the gymnoti are involuntarily attracted by the loadstone, and some very respectable scientific authority can be cited in support of this belief.

Humboldt says he tried in a thousand ways this pretended influence of the magnet on the electrical organs, without having ever observed any sensible effect.

Iron fillings thrown on the back of the fish remained motionless.

The flesh of the fish is sometimes eaten, but it is not much esteemed.

Wherever the gymnoti abound, they are considered great nuisances.

They kill many more fish than they devour, and all the inhabitants of the water, such as lizards, tortoises, and frogs, dread their society, and will, if possible, avoid their companionship by seeking other pools.— They are even capable of disabling young alligators.

In one river near Uritucu it became necessary to change the direction of a road, because the eels were so numerous that every year they killed a great number of mules of burden as they forded the water.