The deleterious qualities of certain fishes have long been the subject of medical conjectures. It is somewhat singular, and most difficult to account for, that the same fish should be wholesome in some waters, and deadly in others, although under the same latitude, and when, to all appearance at least, no local cause can be discovered to which we might reasonably attribute this fatal property. So powerful and prompt moreover, it is in its action that rapid death will ensue whenever a small portion of the fish has been eaten. Such, for instance, is generally the case with the yellow-bill sprat, the clypea thrissa.

Some naturalists attribute this poison to copper banks, on or near which the fish may feed. The absurdity of this opinion has been fully demonstrated; in the first instance, no such copper banks have been discovered in the West Indies, and these fish abound on the coasts of islands of coral formation. Moreover, it is not likely that this mineral should saturate the animal; and, even if it could produce this effect, the entire body would in all probability be affected, whereas the poison seems to lie in particular parts, chiefly in the intestines, the liver, the fat, &c. This is evident from the practice of fishermen, who can eat poisonous fish with impunity if they have taken the precaution to draw them carefully and salt them. In addition to these observations, the symptoms of the disease thus produced, by no means resemble those of mineral poisons. Dr. Chisholm, who pretends that copper banks do exist in the Windward Islands, is of this opinion. Admitting the facts, it may be asked, have the waters of these seas been impregnated by the copper? if they are not, how can its influence extend to its inhabitants? and why are particular fish only affected? Moreover, although it is well known that certain substances are deleterious to some animals and harmless to others, yet one might fancy that, if the coppery principal of an animal’s flesh could poison, it is not irrational to think that the same deadly substance would also destroy the animal. The presence of this mineral has never been detected by any chemical test; and, if the poison consisted in copper, how could salting the fish destroy it? In opposition to these objections, it has been maintained that fish may be rendered poisonous by feeding on the marine plants that grow upon these deadly banks. Now, unless it could be proved that copper is not injurious to fish, these same lithophyta and zoophyta would no doubt poison them.

However, it is more than probable that it is to a certain injurious food that these dangerous qualities are to be referred. Various plants that grow in these regions are of a poisonous nature to man, although, as I have just observed, they may not be so destructive to fish. The circumstance of the alimentary tube being more poisonous than any other part seems to warrant the conclusion; and I have observed in the West Indies, that the crabs that feed upon banks where the manchineel is to be found, frequently occasion serious, and sometimes fatal accidents. On the coast of Malabar, crabs are poisonous in the month of October, when the blue tithymale abounds.

Whatever may be the causes of this deadly principle, the effects are most rapid. When a large quantity has been taken, the patient soon dies in strong convulsions; but frequently, when the quantity and the nature of the poison have not been sufficient to occasion death, the body becomes emaciated, the cuticle peels off, particularly on the palms of the hands and the soles of the feet, the hair drops, acute pains shoot through every joint, and the sufferer not unfrequently sinks under a lingering disease. In these cases change of climate has been found the most effectual remedy, and a return to Europe becomes indispensable.

The usual symptoms that denote the presence of the poison, are languor, heaviness, drowsiness, great restlessness, flushing of the face, nausea, griping, a burning sensation, at first experienced in the face and eyes, and then extending over the whole body; the pulse, at first hard and frequent, soon sinks, and becomes slow and feeble. In some cases the salivary glands become tumefied with a profuse salivation; and the body, and its perspiration, are as yellow as in the jaundice. These peculiar symptoms have frequently been known to arise after eating the rock-fish.

The remedies that are usually resorted to are stimulants. Capsicum has been considered a powerful antidote; and the use of ardent spirits or cordials has also been strongly urged. It has been observed, that persons who had drunk freely, or who had taken a dram after eating fish that had disordered others, were, comparatively speaking, exempt from the severity of the disease. A decoction of the root of the sour-sop, and an infusion of the flowers of the white cedar and the sensitive plant have also been advised by several West India practitioners.

The practice of putting a silver spoon in the water in which fish is boiled, to ascertain its salubrity, is a popular test that cannot be depended on. Fishermen have observed that fish that have no scales are more apt to prove injurious; and those of uncommon size are looked upon as the most dangerous.

To ascertain whether the nature of the fishes’ food could thus render them poisonous, Mr. Moreau de JonnÊs had recourse to many curious experiments. He took portions of polypes found in the waters reputed dangerous, more particularly the liriozoa CaribÆa, the millepora polymorpha, the gorgonia pinnata, the actinia anemone, &c., and, having enveloped them in paste, he fed fishes with them; but in no one instance was any prejudicial result observed. He tried in the same manner the physalis pelagica of Lamark, which contains an acrid and caustic fluid; but the fish invariably refused it, nor would they touch fragments of the manchineel apple.

Oysters have been known to produce various accidents; and, when they were of a green colour, it has been supposed that this peculiarity was also due to copper banks. This is an absurdity; the green tinge is as natural to some varieties as to the esox belone, whose bones are invariably of the same hue as verdigrise. Muscles frequently occasion feverish symptoms, attended with a red, and sometimes a copper-coloured, efflorescence over the whole body. These accidents appear to arise from some peculiar circumstances. In Boulogne I attended a family in which all the children who had eaten muscles were labouring under this affection, while not another instance of it was observed in the place. In the Bahama Islands I witnessed a fatal case in a young girl who had eaten crabs; she was the only sufferer, although every individual in the family had shared in the meal. The idea of the testaceous mollusca avoiding copper-bottomed vessels, while they are found in abundance on those that are not sheathed, is absurd; this circumstance can be easily explained by the greater facility these creatures find in adhering to wood. There is every reason to believe, that the supposed poisonous oysters found adhering to the copper bottom of a ship in the Virgin Isles, and the occasional accidents amongst the men that ate them, were only so in the observer’s imagination, and that part of the ship’s company were affected by some other causes. Another report, equally absurd, was that of the fish having gradually quitted the Thames and Medway since coppering ships’ bottoms has been introduced! The following may be considered the fish that should be avoided:

I have known accidents arise from the use of the dolphin on the high seas; and, while I was in the West Indies, a melancholy instance of the kind occurred, when the captain, mate, and three seamen of a trading vessel died from the poison; a passenger, his wife, and a boy, were the only survivors, and were fortunately picked up in the unmanageable vessel.

The above catalogue of poisonous fishes is extracted from Dr. Dancer’s “Jamaica Practice of Physic,” and its correctness fell under my own observation in the Wrest Indies. The different systems and classifications of ichthyologists have produced much confusion, and may lead to fatal errors; I think it therefore advisable to submit to travellers, who may have to visit these unhealthy regions, the names of the toxicophorous fishes according to the French momenclature.

A work, in which a synonymous catalogue of all the fishes supposed to be poisonous might be found, would be highly desirable, as they generally bear different popular and scientific names, thus producing a dangerous confusion even amongst naturalists; how much more dangerous amongst seafaring people and voyagers!

I cannot conclude this article without noticing the singular properties of those electric fishes denominated the torpedo-ray and the gymnote. They had been long known to naturalists, and the ancients attributed their destructive faculties to a magic power that Oppian had recorded in his Alieuticon, where he describes a fisherman palsied through the hook, the line, and the rod. This influence being voluntary on the part of the animal, seemed to warrant the belief in its mischievous nature, since it allows itself sometimes to be touched with impunity, while at others it burrows itself under the sand of the beach, when the tide has receded, and maliciously benumbs the astonished passenger who walks over it. This singular fish, which is common in the Mediterranean Sea, has been described both by the Greek and Roman writers; amongst others, by Aristotle and AthenÆus: and Socrates, in his Dialogues, compares a powerful objection, to the influence of the torpedo.

This voluntary faculty has been observed by LacÉpÈde and Cloquet in the Mediterranean, and at La Rochelle. In torpedos kept in water for experimental purposes, RÉaumur found that he handled them without experiencing any shock for some time, until they at last appeared to become impatient: he then experienced a stunning sensation along the arm, not easily to be described, but resembling that which is felt when a limb has been struck with a sudden blow. One of the experiments of this naturalist proved the extensive power of this faculty. He placed a torpedo and a duck in a vessel containing sea-water, covered with linen to prevent the duck from escaping, without impeding the bird’s respiration. At the expiration of a few minutes the animal was found dead, having been killed by the electric shocks of its enemy.

Redi was the first who demonstrated this faculty. Having laid hold of a torpedo recently caught, he had scarcely touched it, when he felt a creeping sensation shooting up to the shoulder, followed by an unpleasant tremor, with a lancinating pain in the elbow. These sensations he experienced as often as he touched the animal; but this faculty gradually decreased in strength as the animal became exhausted and dying. These experiments he related in a work entitled “Esperienze intorno À diverse cose naturali.” Florence, 1671.

In 1774, Walsh made some very interesting experiments at the Isle of RÉ and La Rochelle, and clearly demonstrated this electric faculty in a paper On the electric property of the torpedo. In one of them he found that this fish could produce from forty to fifty shocks in the course of ninety minutes. The electrified individuals were isolated; and at each shock the animal gave, it appeared to labour under a sense of contraction, when its eyes sunk deep in their sockets.

The trichiurus electricus of LinnÆus, the rhinobatus electricus of Schneider, and the gymnonotus electricus of Surinam, are the species of this singular fish with which experiments have chiefly been made. The gymnonotus is a kind of eel, five or six feet in length, and its electric properties are so powerful that it can throw down men and horses. This animal is rendered more terrific from the velocity of his powers of natation, thus being able to discharge its thunder far and near. When touched with one hand the shock is slight; but when grasped with both, it is so violent that, according to the accounts of Collins Flag, the electric fluid can paralyze the arms of the imprudent experimentalist for several years. This electric action is analogous to that which is obtained by means of the fulminating plate, which is made of glass with metallic plates. Twenty-seven persons holding each other by the hands, and forming a chain, the extremities of which corresponded with the points of the fish’s body, experienced a smart shock. These shocks are produced in quick succession, but become gradually weaker as the fluid appears to be exhausted. Humboldt informs us, that, to catch this fish, wild horses are driven into the water, and after having expended the fury and the vigour of the gymnonotus, fishermen step in and catch them either with nets or harpoons. Here we find that the irritable or sensorial power is exhausted through the medium of electricity. These phenomena may be attributed to an electric or Voltaic aura; and the organ of the animal that secretes the fluid resembles in its wonderful structure the Voltaic apparatus. Both the gymnote and the torpedo obey the laws of electricity, and their action is limited to the same conducting and non-conducting mediums. The electric sparks proceeding from the gymnote have been plainly seen in a dark chamber by Walsh, Pringle, Williamson, and others. The fish has four electric organs, two large and two small ones, extending on each side of the body from the abdomen to the end of the tail. These organs are of such a size that they constitute one third of the fish’s bulk. Each of them is composed of a series of aponeurotic membranes, longitudinal, parallel, horizontal, and at about one line’s distance from each other. Hunter counted thirty-four of these fasciculi in one of the largest. Other membranes or plates traverse these vertically, and nearly at a right angle; thus forming a plexus or net-work of numerous rhomboidal cells. Hunter found no less than two hundred and forty of these vertical plates in the space of eleven inches.

This apparatus, analogous to the Voltaic pile, is brought into action by a system of nerves rising from the spinal marrow, each vertebra giving out a branch; other branches, rising from a large nerve, running from the basis of the cranium to the extremity of the tail. All these ramifications are spread and developed in the cells of the electric organs, to transmit its powerful fluid, and strike with stupor or with death every animal that comes within its reach. LacÉpÈde has justly compared this wonderful mechanism to a battery formed of a multitude of folio-electric pieces.

The electric organ of the malapterus electricus is of a different formation. This fish, found in the Nile and in other rivers of Africa, is called by the Arabs raash or thunder. In this animal the electric fluid extends all round the body, immediately under the integuments, and consists of a tissue of cellular fibres so dense, that it might be compared to a layer of bacon; but, when carefully examined, it consists of a series of fibres forming a complex net-work. These cells, like those in the gymnote, are lubricated with a mucous secretion. The nervous system of this intricate machinery is formed by the two long branches of the pneumo-gastric nerves, which in fishes usually run under each lateral line. Here, however, they approach each other on leaving the cranium, traversing the first vertebra.

LinnÆus had classed the torpedo in the genus ray, and hence called it raia torpedo. Later naturalists have restored to it its ancient name, as given by Pliny, and termed it torpedo, of which four species are described: the T. narke, or with five spots; the T. unimaculata, marked, as the name indicates, with one spot; the T. marmorata, and the T. Galvanni.

The ancients placed much faith in the medicinal properties of these fishes. Hippocrates recommends its roasted flesh in dropsies that follow liver affections. Dioscorides prescribed its application in cases of obstinate headaches and rheumatisms. Galen and other physicians recommend the application of the living animal; and Scribonius Largus states that the freedman Anteroes was cured of the gout by this practice. To this day, in Abyssinia, fever patients are tied down on a table, and a torpedo is applied to various parts of the body. This operation, it is affirmed, causes great pain, but is an infallible remedy.