THE GYMNOTUS, OR ELECTRICAL EEL.

Extract from Baron Humboldt's Personal Narrative of Travels to the Equinoctial Regions of the New Continent. Vol. 4.

I was impatient, from the time of my arrival at Cumana, to procure electrical eels.

We had been promised them often, but our hopes had always been disappointed.

Money loses its value as you withdraw from the coast; and how is the imperturbable phlegm of the vulgar to be vanquished, when they are not excited by the desire of gain?

The Spaniards confound all electrical fishes under the name of tembladores, (producers of trembling, literally tremblers.)

There are some in the Caribbean sea, on the coast of Cumana.

The Guayqueria Indians, who are the most skilful and industrious fishermen in those parts, brought us a fish, which, they said, had benumbed their hands.

This fish ascends the little river Manzanares. It is a new species of the ray, the lateral spots of which are scarcely visible, and which much resembles the torpedo of Galvani.

The torpedoes, furnished with an electric organ that is externally visible, on account of the transparency of the skin, form a genus or subgenus, different from the rays properly so called.

The torpedo of Cumana was very lively, very energetic in its muscular movements, and yet the electrical shocks it gave us were extremely feeble.

They became stronger on galvanizing the animal by the contact of zinc and gold.

Other tembladores, real gymnoti or electrical eels, inhabit the Rio Colorado, the Guarapiche, and several little streams that cross the missions of the Chayma Indians.

They abound also in the large rivers of America, the Oroonoko, the Amazon, and the Meta: but the strength of the current, and the depth of the water, prevent their being caught by the Indians.

They see these fish less frequently than they feel electrical shocks from them when swimming or bathing in the river.

In the Llanos, particularly in the environs of Calabozo, between the farms of Morichal and the missions de arriba and de abaxo, the basins of stagnant water, and the confluents of the Oroonoko (the Rio Guarico and the Canos of Rastro, Berito, and Paloma) are filled with electrical eels.

We at first wished to make our experiments in the house we inhabited at Calabozo; but the dread of the electrical shocks of the gymnoti is so great, and so exaggerated among the vulgar, that during three days we could not obtain one, though they are easily caught, and we had promised the Indians two piastres for every strong and vigorous fish.

This fear of the Indians is the more extraordinary, as they do not attempt to employ means in which they profess to have great confidence.

When interrogated on the effect of the tembladores, they never fail to tell the whites that they may be touched with impunity, while you are chewing tobacco.

This fable of the influence of tobacco on animal electricity is as general on the continent of South America, as the belief among mariners of the effect of garlic and tallow on the magnetic needle.

Impatient of waiting, and having obtained very uncertain results from an electrical eel that had been brought to us alive, but much enfeebled, we repaired to the Cano de Bera, to make our experiments in the open air, on the borders of the water itself.

We set off on the 19th of March, at a very early hour, for the village of Rastro de abaxo; thence we were conducted by the Indians to a stream, which, in the time of drought, forms a basin of muddy water, surrounded by fine trees, the clusia, the amyris, and the mimosa with fragrant flowers.

To catch the gymnoti with nets is very difficult, on account of the extreme agility of the fish, which bury themselves in the mud like serpents.

We would not employ the barbasco, that is to say, the roots of the piscidea erithryna, jacquinia armillaris, and some species of phyllanthus, which, thrown into the pool, intoxicate or benumb these animals.

These means would have enfeebled the gymnoti; the Indians, therefore, told us, that they would "fish with horses," embarbascar con cavallos.

We found it difficult 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.

They brought about thirty with them, which they forced to enter the pool.

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, surround the pool closely; and some 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 electric 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 endeavour 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 vigilance of the fisherman.

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 coeliacus 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 only 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.

When the cords are very dry the Indians feel no shock in raising the fish into the air.

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

Some were taken by the same means toward the evening.

The temperature of the waters in which the gymnoti habitually live, is from 26° to 27°.

Their electric force diminishes, it is said, in colder waters; and it is remarkable, that in general, as a celebrated naturalist has already observed, animals endowed with electromotive organs, the effects of which are sensible to man, are not found in the air, but in a fluid that is a conductor of electricity.

The gymnotus is the largest of electrical fishes.

I measured some that were from five feet to five feet three inches long; and the Indians assert that they have seen still longer.

We found that a fish of three feet ten inches long weighed twelve pounds.

The transverse diameter of the body, without reckoning the anal fin, which is elongated in the form of a keel, was three inches five lines.

The gymnoti of Cano de Bera are of a fine olive green.

The under part of the head is yellow, mingled with red.

Two rows of small yellow spots are placed symmetrically along the back, from the head to the end of the tail.

Every spot contains an excretory aperture.

In consequence, the skin of the animal is constantly covered with a mucous matter, which, as Volta has proved, conducts electricity twenty or thirty times better than pure water.

It is, in general, somewhat remarkable, that no electrical fish, yet discovered in the different parts of the world, is covered with scales.

The gymnoti, like our eels, are fond of swallowing and breathing air on the surface of the water; but we must not thence conclude with Mr.

Bajon, that the fish would perish if it could not come up to breathe the air.

Our eels wander a part of the night upon the grass, while I have seen a very vigorous gymnotus, that had sprung out of the tub, die on the ground.

Mr. Provencal and myself have proved, by our researches on the respiration of fishes, that their humid bronchiae can execute the double function of decomposing the atmospheric air, and of appropriating the oxygen dissolved in water.

They do not suspend their respiration in the air; but they absorb the gazeous oxygen, like a reptile furnished with lungs.

It is known that carp may be fattened by being fed out of the water, and wetting their gills from time to time with humid moss, to prevent their drying.

Fish separate their gill covers wider in oxygen gas, than in water.

Their temperature, however, does not rise; and they live the same length of time in pure vital air, and in a mixture of ninety parts azot, and ten oxygen.

We found, that tench (cyprinus tinca) placed under inverted jars filled with air, absorb half a cubic centimetre of oxygen in an hour.

This action takes place in the gills only; for fishes, on which a collar of cork has been fastened, and leaving their head out of the jar filled with air, do not act upon the oxygen by the rest of their body.

It would be temerity to expose ourselves to the first shocks of a very large and strongly irritated gymnotus.

If by chance you receive a stroke before the fish is wounded or wearied by a long pursuit, the pain and numbness are so violent that it is impossible to describe the nature of the feeling they excite.

I do not remember having ever received from the discharge of a large Leyden jar, a more dreadful shock than that which I experienced by imprudently placing both my feet on a gymnotus just taken out of the water.

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

To be aware of the difference, which is sufficiently striking, that exists between the sensation produced by the pile of Volta and an electrical fish, the latter should be touched when they are in a state of extreme weakness.

The gymnoti and the torpedoes then cause a twitching, which is propagated from the part that rests on the electric organs as far as the elbow.

We seem to feel at every stroke an internal vibration that lasts two or three seconds, and is followed by a painful numbness.

Accordingly, the Tamanac Indians call the temblador, in their expressive language, arimna, which means something that deprives of motion.

The sensation caused by the feeble shocks of an electrical eel appeared to me analogous to that painful twitching, with which I have been seized at each contact of two heterogeneous metals applied to wounds, which I had made on my back by means of cantharides.

This difference of sensation between the effects of electrical fishes and those of the pile, or a Leyden vial weakly charged, has struck every observer; there is, however, nothing in this contrary to the supposition of the identity of electricity and the galvanic action of fishes.

The electricity may be the same; but its effects will be variously modified by the disposition of the electrical apparatus, by the intensity of the fluid, by the rapidity of the current, and by a particular mode of action.

In Dutch Guyana, at Demerary, for instance, electrical eels were formerly employed to cure the paralytic.

At a time when the physicians of Europe had a great confidence in the effects of electricity, a surgeon of Essequibo, Mr. Vander Lott, published in Holland a treatise on the medical properties of the gymnoti.

These electrical cures are found among the savages of America, as well as among the Greeks.

We are told by Scribonius Largus, Galen, and Dioscorides, that torpedoes cure the headache and the gout.

I did not hear of this species of remedy in the Spanish colonies which I visited; but I can assert, that, after having made experiments during four hours successively with gymnoti, Mr. Bonpland and myself felt till the next day a debility in the muscles, a pain in the joints, and a general uneasiness, which was the effect of a strong irritation of the nervous system.

Gymnoti are neither charged conductors, nor batteries, nor electromotive apparatuses, the shock of which is received every time they are touched with one hand, or when both hands are applied to form a conducting circle between two heterogeneous poles.

The electric action of the fish depends entirely on its will; whether because it do not keep its electric organs always charged, or by the secretion of some fluid, or by any other means alike mysterious to us, it be capable of directing the action of its organs to an external object.

We often tried, both insulated and uninsulated, to touch the fish, without feeling the least shock.

When Mr. Bonpland held it by the head, or by the middle of the body, while I held it by the tail, and, standing on the moist ground, did not take each others hand, one of us received shocks which the other did not feel.

It depends upon the gymnotus to act toward the point, where it finds itself the most strongly irritated.

The discharge is then made at one point only, and not at the neighbouring points.

If two persons touch the belly of the fish with their fingers, at an inch distance, and press it simultaneously, sometimes one, sometimes the other, will receive the shock.

In the same manner, when one insulated person holds the tail of a vigorous gymnotus, and another pinches the gills, or pectoral fin, it is often the first only by whom the shock is received.

It did not appear to us that these differences could be attributed to the dryness or dampness of our hands, or to their unequal conducting power.

The gymnotus seemed to direct its strokes sometimes from the whole surface of its body, sometimes from one point only.

This effect indicates less a partial discharge of the organ composed of an innumerable quantity of leaves, than the faculty which the animal possesses, perhaps by the instantaneous secretion of a fluid spread through the cellular membrane, of establishing the communication between its organs and the skin only, in a very limited space.

Nothing proves more strongly the faculty which the gymnotus possesses, of darting and directing its stroke according to its will, than the observations made at Philadelphia, and recently at Stockholm, on gymnoti rendered extremely tame.

When they had been made to fast a long time, they killed from afar small fishes put into the tub.

They acted at a distance; that is to say, their electrical stroke passed through a very thick stratum of water.

We need not be surprised, that what was observed in Sweden on a single gymnotus only, we could not see on a great number of individuals in their native country.

The electric action of animals being a vital action, and subject to their will, it does not depend solely on their state of health and vigour.

A gymnotus that has made the voyage from Surinam to Philadelphia and Stockholm, accustoms itself to the imprisonment, to which it is reduced; it resumes, by degrees, the same habits in the tub, which it had in the rivers and pools.

An electrical eel was brought to me at Calabozo, taken in a net, and, consequently, having no wound.

It ate meat, and terribly frightened the little tortoises and frogs, which, not knowing the danger, placed themselves with confidence on its back.

The frogs did not receive the stroke till the moment when they touched the body of the gymnotus.

When they recovered, they leaped out of the tub; and when replaced near the fish, they were frightened at its sight only.

We then observed nothing that indicated an action at a distance; but our gymnotus, recently taken, was not yet sufficiently tamed to attack and devour frogs. On approaching the finger, or metallic points, within the distance of half a line from the electric organs, no shock was felt.

Perhaps the animal did not perceive the neighbourhood of this foreign body; or, if it did, we must suppose, that the timidity it felt in the commencement of its captivity, prevented it from darting forth its energetic strokes, except when strongly irritated by an immediate contact.

The gymnotus being immersed in water, I approached my hand, both armed and unarmed with a metal, within the distance of a few lines from the electric organs; yet the strata of water transmitted no shock, while Mr.

Bonpland irritated the animal strongly by an immediate contact, and received some very violent shocks.

If I had plunged the most delicate electroscopes we know, prepared frogs, into contiguous strata of water, they would no doubt have felt contractions at the moment when the gymnotus seemed to direct its stroke elsewhere.

Prepared frogs, placed immediately on the body of a torpedo, experience, according to Galvani, a strong contraction at every discharge of the fish.

The electrical organ of the gymnoti acts only under the immediate influence of the brain and the heart.

On cutting a very vigorous fish through the middle of the body, the fore part alone gave me shocks.

The shocks are equally strong, in whatever part of the body the fish is touched; it is most disposed, however, to dart them forth when the pectoral fin, the electrical organ, the lips, the eyes, or the gills, are pinched.

Sometimes the animal struggles violently with a person holding it by the tail, without communicating the least shock.

Nor did I feel any when I made a slight incision near the pectoral fin of the fish, and galvanized the wound by the simple contact of two pieces of zinc and silver.

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

The most violent muscular movements are not always accompanied by electric discharges.

The action of the fish on the organs of man is transmitted and intercepted by the same bodies that transmit and intercept the electrical current of a conductor charged by a Leyden vial, or Volta's pile.

Some anomalies, which we thought we observed, are easily explained, when we recollect, that even metals (as is proved from their ignition when exposed to the action of the pile) present a slight obstacle to the passage of electricity; and that a bad conductor annihilates the effect of a feeble electricity on our organs, while it transmits to us the effect of a very strong electricity.

The repulsive force that zinc and silver exercise between each other, being far superior to that between gold and silver, I have found, that when a frog, prepared and armed with silver, is galvanized under water, the conducting arc of zinc produces contractions as soon as one of its extremities approaches the muscles within three lines distance; while an arc of gold does not excite the organs, when the stratum of water between the gold and the muscles is more than half a line thick.

In the same manner, by employing a conducting arc composed of two pieces of zinc and silver soldered together endwise, and resting as before, one of the extremities of the metallic arc on the ischiatic nerve, it is necessary, in order to produce contractions, to bring the other extremity of the conducting arc nearer and nearer to the muscles, in proportion as the irritability of the organs diminishes.

Toward the end of the experiment, the slightest stratum of water prevents the passage of the electrical current, and it is only by the immediate contact of the arc with the muscles, that the contractions take place.

I dwell on these effects, dependent on three variable circumstances: the energy of the electromotive apparatus, the conductibility of the medium, and the irritability of the organs that receive the impressions; as it is because experiments have not been sufficiently multiplied with a view to these three variable elements, that, in the action of electrical eels and torpedoes, the accidental circumstances have been taken for absolute conditions, without which the electric shocks are not felt.

In wounded gymnoti, which give feeble, but very equal shocks, these shocks appeared to us constantly stronger on touching the body of the fish with a hand armed with metal, than with the naked hand.

They are stronger also, when, instead of touching the fish with one hand, naked, or armed with metal, we press it at once with both hands, either naked or armed.

These differences, I repeat, become sensible only when you have gymnoti enough at your disposal to be able to choose the weakest; and the extreme equality of the electric discharges admits of distinguishing between the sensations felt alternately by the hand naked or armed with a metal, by one or both hands naked, and by one or both hands armed with metal.

It is also in the case only of small shocks, weak and uniform, that the shocks are more sensible on touching the gymnotus with one hand (without forming a chain) with zinc, than with copper or iron.

Resinous substances, glass, very dry wood, horn, and even bones, which are generally believed to be good conductors, prevent the action of the gymnoti from being transmitted to man. I was surprised at not feeling the least shock on pressing wet sticks of sealing wax against the organs of the fish, while the same animal gave me the most violent strokes, when excited by means of a metallic rod.

Mr. Bonpland received shocks when carrying a gymnotus on two cords of the fibres of the palmtree, which appeared to us extremely dry.

A strong discharge makes its way through very imperfect conductors.

Perhaps, also, the obstacle which the conducting arc presents, renders the discharge more painful.

I touched the gymnotus with a wet pot of brown clay, without effect; yet I received violent shocks when I carried the gymnotus in the same pot, because the contact was greater.

When two persons, insulated or not insulated, hold each other's hands, and one of these persons only touches the fish with the hand, either naked or armed with metal, the shock is most commonly felt by both at once.

It happens, however, also, that in the most painful shocks, the person who comes into immediate contact with the fish alone feels the shock.

When the gymnotus is exhausted, or in a very weak state of excitability, and will no longer emit strokes on being irritated with one hand, the shocks are felt in a very vivid manner, on forming the chain, and employing both hands.

Even then, however, the electric shock takes place only at the will of the animal. Two persons, one of whom holds the tail, and the other the head, cannot, by joining hands and forming a chain, force the gymnotus to dart his stroke.

In employing very delicate electrometers in a thousand ways, insulating them on a plate of glass, and receiving very strong shocks, which passed through the electrometer, I could never discover any phenomenon of attraction or repulsion.

The same observation was made by Mr.

Fahlberg at Stockholm.

This philosopher, however, has seen an electric spark, as Walsh and Ingenhousz had done before him at London, by placing the gymnotus in the air, and interrupting the conducting chain by two gold leaves pasted upon glass, and a line distant from each other.

No person, on the contrary, has ever perceived a spark issue from the body of the fish itself.

We have irritated it for a long time during the night, at Calabozo, in perfect darkness, without observing any luminous appearance.

Having placed four gymnoti of unequal strength in such a manner as to receive the shocks of the most vigorous fish by communication, that is to say, by touching only one of the other fishes, I did not observe that these last were agitated at the moment when the current passed by their bodies.

Perhaps the current established itself on the humid surface of the skin.

We will not, however, conclude from this, that the gymnoti are insensible to electricity; and that they cannot fight with each other at the bottom of the pools.

Their nervous system must be subject to the same agents as the nerves of other animals.

I have, indeed, seen, that, on baring their nerves, they undergo muscular contractions at the simple contact of two heterogeneous metals; and Mr. Fahlberg, of Stockholm, found, that his gymnotus was convulsively agitated when placed in a copper vessel, and feeble discharges from a Leyden vial passed through its skin.

After the experiments I had made on gymnoti, it became highly interesting to me, at my return to Europe, to know with precision the various circumstances in which another electrical fish, the torpedo of our seas, gives, or does not give, shocks.

Though this fish had been examined by a great number of natural philosophers, I found all that had been published on its electrical effects extremely vague.

It has been very arbitrarily supposed that this fish acts like a Leyden vial, which may be discharged at will, by touching it with both hands; and this supposition appears to have led observers into error, who have devoted themselves to researches of this kind. Mr. Gay-Lussac and myself, during our journey to Italy, made a great number of experiments on torpedoes taken in the Gulf of Naples.

These experiments furnish many results somewhat different from those I collected on the gymnoti.

It is probable, that the cause of these anomalies proceeds rather from the inequality of electric power in the two fishes, than the different disposition of their organs.

Though the power of the torpedo cannot be compared with that of the gymnoti, it is sufficient to cause very painful sensations.

A person accustomed to electric shocks can with difficulty hold in his hands a torpedo of twelve or fourteen inches, and in possession of all its vigour.

When the animal no longer gives any but very feeble strokes under water, the shocks become more sensible if it be raised above the surface.

I have often observed the same phenomenon in galvanizing frogs.

The torpedo moves the pectoral fins convulsively, every time it emits a stroke; and this stroke is more or less painful, according as the immediate contact takes place by a greater or less surface.

We have above observed, that the gymnotus gives the strongest shocks without making any movement with the eyes, head, or fins.

Is this difference caused by the position of the electric organ, which is not double in the gymnoti? or, does the movement of the pectoral fins of the torpedo directly prove, that the fish restores the electrical equilibrium by its own skin, discharges itself by its own body, and that we generally feel only the effect of a lateral shock?

We cannot discharge at will either a torpedo or a gymnotus, as we discharge at will a Leyden vial or a Voltaic pile.

A shock is not always felt, even in touching the electric fish with both hands.

We must irritate it to make it give the shock.

This action in the torpedoes, as well as in the gymnoti, is a vital action; it depends on the will only of the animal, which, perhaps, does not always keep its electrical organs charged, or does not always employ the action of its nerves to establish the chain between the positive and negative poles.

This is certain, that the torpedo gives a long series of shocks with astonishing celerity: whether it be, that the plates or laminae of his organs are not wholly exhausted, or that the fish recharges them instantaneously.

The electric stroke is felt when the animal is disposed to give it, whether we touch with a single finger only one of the surfaces of the organs, or apply both hands to the two surfaces, the superior and inferior at once.

In either case, it is altogether indifferent, whether the person who touches the fish with one finger, or both hands, be insulated or not.

All that has been said on the necessity of a communication with the damp ground, to establish a circuit, is founded on inaccurate observations.

Mr. Gay-Lussac made the important observation, that, when an insulated person touches the torpedo with one finger, it is indispensable that the contact be immediate.

The fish may with impunity be touched with a key or any other metallic instrument; no shock is felt when a conducting or nonconducting body is interposed between the finger and the electrical organ of the torpedo.

This circumstance furnishes a great difference between the torpedo and the gymnotus, the latter giving his strokes through an iron rod several feet long.

When the torpedo is placed on a metallic plate of very little thickness, so that the plate touches the inferior surface of the organs, the hand that supports the plate never feels any shock, though another insulated person excites the animal, and the convulsive movement of the pectoral fins denotes the strongest and most reiterated discharges.

If, on the contrary, a person support the torpedo, placed upon a metallic plate, with the left hand, as in the foregoing experiment, and the same person touch the superior surface of the electrical organ with the right hand; a strong shock is then felt in both arms.

The sensation is the same when the fish is placed between two metallic plates, the edges of which do not touch, and the person applies both hands at once to these plates.

The interposition of one metallic plate prevents the communication, if that plate be touched with one hand only, while the interposition of two metallic plates does not prevent the shock when both hands are applied.

In the latter case, it cannot be doubted, that the circulation of the fluid is established by the two arms.

If, in this situation of the fish between two plates, there exist any immediate communication between the edges of these two plates, no shock takes place.

The chain between the two surfaces of the electric organ is then formed by the plates; and the new communication established by the contact of the two hands with the two plates, remains without effect.

We carried the torpedo with impunity between two dishes of metal, and felt the strokes it gave only at the instant when the dishes no longer touched each other at the edges.

Nothing in the torpedo, or in the gymnotus, indicates that the animal modifies the electrical state of the bodies by which it is surrounded.

The most delicate electrometer is no way affected, in whatever manner it is employed, whether bringing it near the organs, or insulating the fish, covering it with a metallic plate, and causing the plate to communicate by a conducting wire with the condenser of Volta.

We were at great pains to vary the experiments by which we sought to render the electrical tension in the organs of the torpedo sensible; but they were constantly without effect, and perfectly confirmed what Mr. Bonpland and myself had observed respecting the gymnoti during our abode in South America.

Electrical fishes, when very vigorous, act with the same energy under water and in the air.

This observation led us to examine the conducting property of water; and we found that when several persons form the chain between the superior and inferior surface of the organs of the torpedo, the shock is felt only when these persons have united their hands.

The action is not intercepted if two persons who support the torpedo with their right hands, instead of taking one another by the left hand, plunge each a metallic point into a drop of water placed on an insulating substance.

On substituting flame for the drop of water, the communication is interrupted, and is only re-established, as in the gymnoti, when the two points immediately touch each other in the interior of the flame.