BARON HUMBOLDT'S OBSERVATIONS ON THE GYMNOTUS, OR ELECTRICAL EEL.

The galvanic electricity of the gymnotus causes a sensation which can hardly be said to be specifically distinct from that which is occasioned by the conductor of an electrical machine, a Leyden jar, or even the voltaic pile.

The same observation has been made respecting the torpedo, or electric ray.

In the gymnotus, however, the difference that does exist is the more striking in proportion as the shocks are greater.

No man exposes himself rashly to the first discharges of a strong and highly irritated gymnotus.

If, by accident, a shock be received before the fish is wounded or tired out by the pursuit, this shock is so painful, that it is impossible even to find an expression to describe the nature of the sensation.

I do not remember to have ever experienced, from the discharge of a large-sized Leyden jar, a shock so dreadful as one which I received on placing my feet on a gymnotus which had just been drawn out of the water.

I felt during the rest of the day an acute pain in the knees, and in almost every joint of the body.

A blow upon the stomach, a stone falling on the head, a violent electric explosion, produce instantly the same effect.

We distinguish nothing when the whole nervous system is affected at once. To experience the difference believed to exist between the sensations produced by the voltaic pile and electrical fishes, the latter must be touched when they are reduced to a state of extreme weakness.

In that case we observe, that the electrical eels and torpedos cause twitchings of the muscles (subsultus tendinum), which are propagated along the arm, from the part resting on the electric organ up to the elbow.

This trembling, which is not visible externally, slightly resembles the very slight commotions produced by our artificial electrical apparatuses. M.

Bayon, some time ago, was struck with this difference; and the common people, to characterize the nature of this extraordinary sensation, still confound, so to say, the cause with the effect, and call the gymnotus, Tremblador in the Spanish colonies, and Anguille tremblante in French Guiana.

In fact, on touching these electrical fishes, we seem to feel at every shock a vibration, an internal trembling, which lasts for two or three seconds, and which is followed by a painful numbness.

If the sensation which is experienced on the contact of the electric eel be different from that which is produced by the voltaic pile or Leyden jar, it is, however, very analogous to the pain caused by applying zinc and silver to wounds on the back and on the hand.

These wounds, which I have myself made--one by means of the blistering fly, and the other by a slight incision--have furnished abundant and convincing proof of the relations which exist between the effect of electrical fishes, and that of the galvanic current established by the application of different metals upon the human body.

After having handled gymnoti for four hours consecutively, we felt, even till the next morning, a pain in the joints of the extremities, a debility in the muscles, and a general uneasiness, which was, without doubt, the consequence of a long and violent irritation of the whole nervous system. M. Van der Lott, surgeon at Essequibo, has published in Holland a Memoir on the Medical Properties of the Electrical Eel. Mr. Bancroft assures us, that at Demerara they are employed for the cure of paralytic subjects; but in the Spanish colonies they know nothing of this property in the gymnotus.

The ancients, however, made use of the galvanic electricity of the torpedo, according to Scribonius Largus, in cases of head-ache, megrims, and gout.

And such is all we know respecting medical electricity among the Greeks and the savages of America.

Persons most accustomed to electric shocks support, with repugnance, those given by a torpedo one foot four inches in length; but the power of a gymnotus is ten times greater, as we have seen by its effect upon horses.

It often happens, in taking young crocodiles of two or three feet in length, and little fishes in the same net with gymnoti, that the fishes are found dead, and the crocodile expiring.

The Indians, in such cases, say that the young crocodile had not time to tear the net, because the gymnotus had paralysed and put him hors du combat.

These terrible fishes, although carnivorous and of an aspect hideous as the serpent, are nevertheless in some measure docile, and naturally of a peaceable disposition.

Much less active than our eels, they readily accustom themselves to their new prison; they eat everything that is offered them, but without manifesting a great voracity.

They do not discharge their violent shocks unless irritated; and then especially if tickled along the under part of the body, at the transparent part of the electric organs, at the pectoral fin, the lips, the eyes, and especially if the skin be touched near the gill-cover.

All these parts seem to be the most sensible, for here the skin is thinnest and least loaded with fat.

Fishes and reptiles which have never before felt the shocks of a gymnotus, do not seem to be warned of their danger by any particular instinct.

Although its form and size are rather imposing, a little tortoise which we put into the same tub approached it with confidence; it wanted to hide itself under the eel's belly; but scarcely had it touched it with the end of one of its feet, when it received a shock, too feeble, indeed, to kill it, but strong enough to make it retire as far away as possible.

From that moment the tortoise would no longer remain in the vicinity of the torpedo.

And so, in all the pools or streamlets which it inhabits, one finds very few fishes of any other species.

The gymnotus often kills without devouring its victim.

It instinctively regards as an enemy everything that approaches it.

Like a cloud surcharged with the electric fluid, he comes upon the fish he means to destroy; when at a short distance from it, he rests for a few seconds, necessary perhaps to prepare the storm that is to burst, and then hurls his thunder against his devoted enemy. --From the Voyage of Humbolt and Bonpland.

[The remainder of these observations, with the mode of taking the gymnotus by the natives, will be given in a future Number].