Part 37 (1/2)
La pet.i.te vieille, { _B. monoceros_.--LINN.
{ _Alutus monoceros_.--CUVIER.
Le coffre triangulaire, _Ostracion trigonus_.--BLOCH.
La grande orphie, _Esox Brasiliensis_.--LINN.
La pet.i.te orphie, _E. marginatus_.--LACEPEDE.
Le congre, _Muraena conger_.--MINN.
Le perroquet, _Sparus psittacus_.--LACEPEDE.
Le capitaine, _S. erythrinus_.--BLOCH.
La becune, _Sphyraena becuna_.
Le thon, _s...o...b..r thynnus_.--LINN.
La carangue, _Caranx carangus_.
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 pa.s.senger 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 Athenaeus: and Socrates, in his Dialogues, compares a powerful objection, to the influence of the torpedo.
This voluntary faculty has been observed by Lacepede and Cloquet in the Mediterranean, and at La Roch.e.l.le. In torpedos kept in water for experimental purposes, Reaumur 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 ent.i.tled ”_Esperienze intorno a diverse cose naturali_.” Florence, 1671.
In 1774, Walsh made some very interesting experiments at the Isle of Re and La Roch.e.l.le, 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 Linnaeus, the _rhin.o.batus 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 a.n.a.logous to that which is obtained by means of the fulminating plate, which is made of gla.s.s 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 const.i.tute 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 s.p.a.ce of eleven inches.
This apparatus, a.n.a.logous 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. Lacepede has justly compared this wonderful mechanism to a battery formed of a mult.i.tude 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.
Linnaeus had cla.s.sed 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.
MEMORY AND THE MENTAL FACULTIES.
This n.o.ble faculty, the proudest attribute of mankind, justly called the mother of the Muses, is subject to be impaired by various physical and moral causes, while a similar agency can sometimes restore it to its pristine energy, or develope its powers when sluggish and defective.
Memory may be considered as the history of the past chronicled in our minds, to be consulted and called upon whenever circ.u.mstances stances or the strange complication of human interests demand its powerful aid. Its powers and nature widely differ, and these varieties depend upon education, natural capacities, mode of living, and pursuits. Thus memory has been divided into that faculty that applies to facts, and to that more superficial quality that embraces a recollection of things, to which must be added the memory of localities and words: ”Lucullus habuit divinam quamdam memoriam rerum, verborum majorem Hortensius,” said Cicero.
It is on this division that Aristotle founded his belief that the brute creation had not the faculty of reminiscence, although he allowed them to possess memory. According to his doctrine, reminiscence is the power of recollecting an object by means of a syllogistic chain of thought; an intellectual link with which animals do not seem to be gifted. Their memory appears solely to consist of the impressions received by the return of circ.u.mstances of a similar kind. Thus, a horse that has started on a certain part of a road will be apt to evince the same apprehension when pa.s.sing the same spot. This is an instinctive fear, but not the result of calculation or the combination of former ideas. Reminiscence is the revival of memory by reflection; in short, the recovery or recollection of lost impressions.
The recollection of things or facts can alone bring forth a sound judgment. It implies a regular co-ordination of ideas, a catenation of reflections, in which circ.u.mstances are linked with each other. The chain broken, no conclusion can be drawn. Newton was wont to lose the thread of an important conversation when his mind was in search of an idea. This is the reason why the society of the learned is seldom entertaining to the generality of men. They are considered absent, while their brain is busily employed in pursuits perhaps of great importance; they must therefore be anything but agreeable to those who generally think through the medium of other persons' brains.
The brain is considered to be the seat of memory. When it is injured, remembrance is impaired; and, on the other hand, an accident has been known to improve the recollective faculties. A man remarkable for his bad memory fell from a considerable height upon his head; ever after he could recollect the most trifling circ.u.mstance. The effects of different maladies will also produce various results on this faculty. In some instances names of persons and things are completely forgotten or misapplied; at other times, words beginning with a vowel cannot be found.
Sudden fright and cold have produced the same effects. An elderly man fell off his horse in crossing a ford in a winter's night; ever afterward he could not bring to his recollection the names of his wife and children, although he did not cease to recognise and love them as fondly as before the accident. Cold has been at all times considered injurious to memory; hence Paulus aeginus called Oblivion the child of Cold.
In fevers, and a state of great debility, in a disordered condition of the digestive functions, and various affections of the head, we generally find that the attention cannot long be applied to any one subject or a continued train of thoughts; all past circ.u.mstances are readily forgotten, while pa.s.sing occurrences are most acutely observed and felt, excepting in cases of delirium, when we have the perception of surrounding objects or receive an erroneous impression of their nature and agency. In many cases of this nature, we find that conversation produces great excitement and increases the evil, for the subject of such intercourse is generally misconceived and distorted through the medium of a morbid conception, while the past, the present, and the future are grouped in a confused and most heterogeneous and incoherent jumble.