Galvanism, is the name now commonly given to the influence discovered nearly eight years ago by the celebrated Galvani, professor of anatomy at Bologna, and which, by him and some other authors, has been called animal electricity. We prefer the former name, because we think it by no means proved, that the phenomena discovered by Galvani depend either upon the electric fluid, or upon any law of animal life. While that is the case, it is surely better to distinguish a new branch of science by the name of the inventor, than to give it an appellation which probably may, and, in our opinion, certainly does, lead to an erroneous theory.

M. Galvani was engaged in a set of experiments, the object of which was to demonstrate, if possible, the dependence of muscular motion upon electricity. In the course of this investigation, he had met with several new and striking appearances which were certainly electrical; soon after which, a fortunate accident led to the discovery of the phenomena which constitute the chief subject of this article. The strong resemblance which these bore to the electrical facts which he had before observed, led almost irresistibly to the conclusion that they all depended upon the same cause. This opinion he immediately adopted; and his subsequent experiments and reasonings were naturally directed to support it. The splendor of his discovery dazzled the imaginations of those who prosecuted the enquiry; and for some time his theory, in so far at least as it attributed the whole to the agency of the electric fluid, was sanctioned by universal approbation. Of late, however, this opinion has rather lost ground; and there are now many philosophers who consider the phenomena as totally unconnected with electricity.

We propose, in the first place, to enumerate the chief facts which have been ascertained on the subject; we shall then enquire, whether or not the cause of the appearances be the electric fluid; and, thirdly, we shall examine how far it has been proved, that this cause is necessarily connected with animal life.

Whilst Galvani was one day employed in dissecting a frog, in a room where some of his friends were amusing themselves with electrical experiments, one of them having happened to draw a spark from the conductor at last, when arrived at its full perfection, they range themselves parallel to the lips of the calyx, and perpendicular to the stamens, in the same order as a rose. The common receptacle of the flower is oblong, and very capacious, of a yellow colour, and covered with small leaves like hair. The filie is plain, simple, and upright, and covered at the bottom with a tuft of down, and is below the common receptacle of the flower.

Our author says that he has observed, in the middle of a very hot day, that the flowers unbend themselves more, the calyx seems to expand, and the whole flower to turn itself towards the sun in the same manner as does the sunflower. When the branch is cut, the flower dries as it were instantaneously, so that it seems to contain very little humidity. which the frogs were placed, he at length discovered that he could produce the movements at pleasure by touching the animals with two different metals, which, at the same time, touched one another either immediately or by the intervention of some other substance capable of conducting electricity.

All the experiments that have yet been made may be reduced to the following, which will give the otherwise uninformed reader a precise notion of the subject.

Lay bare about an inch of a great nerve, leading to any limb or muscle. Let that end of the bared part which is farthest from the limb be in close contact with a bit of zinc. Touch the zinc with a bit of silver, while another part of the silver touches, either the naked nerve, if not dry, or, whether it be dry or not, the limb or muscle to which it leads. Violent contractions are produced in the limb or muscle, but not in any muscle on the other side of the zinc.

Or, touch the bared nerve with a piece of zinc, and touch, with a piece of silver, either the bared nerve, or the limb; no convulsion is observed, till the zinc and silver are also made to touch each other.

A fact so new, illustrated by many experiments and much ingenious reasoning, which Professor Galvani soon published, could not fail to attract the attention of physiologists all over Europe; and the result of a vast number of experiments, equally cruel and surprising, has been from time to time laid before the public by Valli, Fowler, Monro, Volta, Humboldt, and others.

Frogs, unhappily for themselves, have been found the most convenient subjects for these experiments, as they retain their muscular irritability and susceptibility of the galvanic influence very long. Many hours after they have been decapitated, or have had their brain and spinal marrow destroyed, strong convulsions can be produced in them by the application of the metals. A leg separated from the body will often continue capable of excitement for several days. Nay, very distinct movements have been produced in frogs pretty far advanced in the process of putrefaction. Different kinds of fishes, and many other animals both of cold and warm blood, have been subjected to similar experiments, and have exhibited the same phenomena; but the warm blooded animals lose their susceptibility of galvanism, as of every other stimulus, very soon after death.

Almost any two metals will produce the movements; but, it is believed, the most powerful are the following, in the order in which they are here placed: 1. Zinc; 2. Tin; 3. Lead; in conjunction with, 1. Gold; 2. Silver; 3. Molybdenum; 4. Steel; 5. Copper. Upon this point, however, authors are not perfectly agreed.

The process by which these singular phenomena are produced, consists in effecting, by the use of the exciting apparatus, a mutual communication between any two points of contact, more or less distant from one another, in a system of nervous and muscular organs. The sphere of this mutual communication may be regarded as a complete circle, divided into two parts. That part of it which consists of the organs of the animal under the experiment, has been called the animal arc; that which is formed by the galvanic instruments has been called the excitatory arc. The latter usually consists of more pieces than one; of which some are named flags, brushes, &c., others communicators, from their respective uses.

A very numerous train of experiments on galvanism has been made by a committee of the Physical and Mathematical Class of the National Institute of France; and as their report comprehends a vast number of the most important facts which are yet known on the subject, we shall present our readers with the substance of it (a).

The immense mass of matter which resulted from the experiments of the committee, is, in their report, presented, not in the order in which the experiments were made, but in a sort of classification, by means of which a more distinct knowledge of the subject is obtained at one view. The facts are arranged under these five heads:

1. Refutes of the different combinations and dispositions of the parts of the animal arc. 2. Account of what has been observed of the nature and the different dispositions of the excitatory arc. 3. Circumstances not entering into the composition of the galvanic circle, which, nevertheless, by their influence, modify, alter, or entirely prevent the success of the experiments. 4. Means proposed for varying, diminishing, or restoring the sensibility to galvanism. 5. Attempts to compare the phenomena of galvanism with those of electricity.

Additional experiments, performed by M. Humboldt, in the presence of the members of the committee; which have a reference to several of the proofs stated in the foregoing articles.

I. To the number of twenty experiments were made on the animal arc. The first seven of these were directed to ascertain the relations between the nerves and those muscles over which they are distributed. In the last thirteen, the nerves were cut asunder, or subjected to ligatures; the section or ligature being always between the extremities of the arc. Nerves taken from different animals, or from different parts of the same animal, and joined in one and the same arc, were among the particular subjects of these experiments; as were also the solitary nerve, and the solitary muscle, included between the extremities of the excitatory arc. There were interposed, too, in the course of these experiments, portions of nerves, and of muscles, distinct from those parts. And, in some of the experiments, the animal was without the skin and the epidermis.

The following are inferences which have been deduced from these experiments:

1. The animal arc may consist either of nerves and muscles together, or of nerves alone, without muscles. 2. Nerves are, therefore, the essential part of the animal arc.

(a) The members of the committee were, M. M. Coulomb, Sabatier, Pelletan, Charles, Fourcroy, Vauquelin, Guyton, alias Morveau, and Hallé. M. M. Venturi, De Modene, and M. Humboldt, assisted in the experiment.

(b) We are strongly inclined to doubt the truth of this proposition. Dr Fowler was at first led to think that contractions could be excited in a limb without the metals having any communication with it, except through the medium of the nerve. Recollecting, however, that a very small quantity of moisture serves as a conductor of galvanism, he suspected, and our opinion perfectly coincides with his, that in every case where contractions are.

The muscles are always more or less intersected by the nerves; and are, consequently, in part, a nervous organ.

3. All the parts of the animal are must be either mutually continuous, or at least contiguous to one another. But even contiguity is sufficient to enable the galvanic phenomena to take place.

4. The section or ligature of a nerve interrupts not the galvanic phenomena, if the parts which are cut are under or bound up still remain in close contiguity to one another.

5. No diversity of the parts forming the animal arc, though these be taken from different parts of the same animal, or even from different animals, will have power to impair its galvanic susceptibility, provided only that these parts be still mutually contiguous.

6. If the integrity or galvanic susceptibility of the animal arc be suspended by the separation of any of its parts to some distance from one another, it may be restored by the interposition of some substances, not of an animal nature, between the divided parts. Metallic substances are in particular fit for this use. But the mutual contiguity of all the substances entering into the composition of the arc must ever be carefully preserved. Mr Humboldt discovered that a bit of fresh morel (Helvella mitra Linn.) will supply the place of a part of the nerve.

7. The muscular organs which indicate, by contraction, the presence of the galvanic influence, are always those in which the nerves of a complete animal arc have their ultimate termination.

From this it follows, that the muscles affected by galvanism are always those corresponding to that extremity of the arc which is the most remote from the origin of the nerves of which it is composed.

8. When all the nerves of the animal arc originate towards one of its extremities, then only those muscles which correspond with the opposite extremity are susceptible of galvanic convulsions.

9. When an animal arc consists of more than one system of different nerves, which have all their origin about the middle of the arc, then will the muscles of these several systems of nerves be moved alike at both the extremities of the arc.

10. It seems likewise to appear, from a variety of these experiments, that the opinion of those is inadmissible, who ascribe the phenomena of galvanism to the concurrence of two different and reciprocally corresponding influences, one belonging to the nerve, the other to the muscle, and who compare the relations between the nerve and the muscle, in these phenomena, to those between the interior and the exterior coating of the Leyden phial.

11. It appears, lastly, that the covering of the epidermis, in the entire animal body, acts as an obstacle to the decisive display of the effects of galvanism; and that,

are produced in a limb, without any apparent communication between the metals and the muscles, except through the medium of a nerve, the communication is in fact completed by the moisture upon the surface of the nerve. In this case, the animal arc may be considered as consisting of three pieces, disposed in the following order; the nerve, the muscle, and the water adhering to the surface of the nerve. The latter, indeed, ought rather to be considered as a part of the excitatory arc. "When a nerve (says Dr Fowler), which for some time has been detached from surrounding parts, is either carefully wiped quite dry with a piece of fine muslin, or (let this should be thought to injure its structure) suffered to remain suspended till its moisture has evaporated, no contractions can be excited in the muscles, to which it is distributed, by touching it alone with any two metals in contact with each other; but if it be again moistened with a few drops of water, contractions instantly take place. And, in this way, by alternately drying and moistening the nerve, contractions may at pleasure be alternately suspended and renewed for a considerable time. It may, indeed, be contended, that the moisture softened, and thus restored elasticity and free expansion to the dried cellular membrane surrounding the fibres, of which the trunk of a nerve is composed; and thus, by removing constraint, gave free play to their organization.

"But from observing, that in every other instance where contractions are produced by the mutual contact of the metals, a conducting substance is interposed between them and the muscles as well as between them and the nerve; I think it would be unphilosophical not to allow, that, in the instance in question, the moisture, adhering to the surface of the nerve, formed that requisite communication between the metals and the muscles." We know of no accurate experiment by which it has ever been shewn, that contractions can be produced in a limb without a communication being established between the metals and nerve, and again between the muscles and the metals, either directly, or through some medium capable of conducting galvanism.

To remove the only objection which can be made to Dr Fowler's experiment, and of which we have seen that he was himself aware, namely, that the nerve while dry is incapable of performing its functions, we repeated it in the following manner: A small, but vigorous and lively, male frog was decapitated, and the sciatic nerve being laid bare from the knee upwards, was cut through where it passes out of the pelvis. Fifteen minutes after the head was cut off, the nerve having been cautiously separated from the surrounding parts, and coated with tinfoil in the usual manner, a silver probe was applied to it and its coating, without any other communication with the muscles, and strong contractions took place in the leg. The nerve was now very carefully dried with a piece of fine linen, and the probe was applied as before to the tinfoil and the nerve; no movement whatever took place. Things remaining precisely in this situation, one end of the probe being still in contact with the nerve and its coating, the other end was applied to the muscles of the thigh, and the leg immediately contracted as strongly as ever. Upon moistening the nerve, the contractions were again produced by applying the probe to the nerve and tinfoil alone. We find from this experiment, which we have several times repeated with the utmost care, and with the same result, that the dry nerve retained its functions completely. This appears to us perfectly decisive of the question. that, though from its extreme tenacity, it may not altogether prevent these effects, yet it cannot but very materially diminish them.

II. The Excitatory Arc is usually formed of three different pieces, made of different metals. Of these, one must be in contact with the nerve; the other must touch the muscle; and the third must form the mean of communication between these two. This arrangement, though not indispensably necessary, is at least the most convenient.

In respect to the excitatory arc, the committee examined, 1st, The application of metallic substances to form it; in respect to which they endeavoured to ascertain the number and the diversity of the pieces of metal, of which this may be composed; the metallic mixtures or alloys which are capable of being employed for this use; the particular degree of the friction of one metal upon another, which is favourable to the exhibition of the phenomena; the different states, in respect to galvanism, of metals differently mineralized. 2dly, The effects of the use of carbonic substances in forming the excitatory arc. 3dly, The effects in the same formation, of bodies, which are either non-conductors, or else very imperfect conductors of electricity, such as jet, asphaltus, sulphur, amber, sealing-wax, diamond, &c. 4thly, The consequences of the interposition of water, and of substances moistened with water, between the different parts of the excitatory arc. In forming their excitatory arcs, too, they made themselves the chord of the arc; they introduced into it animal substances which had lost their vitality; they rubbed the supporters with the dry fingers, so as to mark them with nothing but the traces of the perspiration from the skin. They made, likewise, some experiments for the purpose of ascertaining the relations between, on the one hand, the extent and magnitude of the surfaces of the parts composing the arc, and on the other, the effects produced by its energy. From their experiments they have also drawn some inferences concerning the relative efficiencies of the several constituent parts of the exciting arc. It is impossible for us here to relate in detail all this train of experiments. The following corollaries express the substance of those general truths, which their authors were led to infer from them.

1. The excitatory arc possesses the greatest power of influencing galvanism, when it is composed of at least three distinct pieces; each of a peculiar nature: the metals, water, and humid substances, carbonaceous matters, and animal substances, stripped of the epidermis, being the only materials out of which these pieces may be formed.

2. Nevertheless the excitatory arc appears to be not destitute of exciting energy, even when it consists but of one piece or of several pieces, all of one proper substance (c). In general it must be owned, identity of nature in the constituent pieces, and particularly in the supports forming the extremities of the arc, diminishes, in a very sensible manner, its galvanic energy.

3. The slightest difference of nature induced upon the parts, whether by any feeble alloy, or by friction with extraneous substances, is at any time sufficient to communicate to the excitatory arc that full power in which the identity of its composition may have made it defective.

4. As the animal arc is susceptible of being in part made up of metallic substances, or such others as are adapted to enter into the composition of the excitatory arc; so, on the other hand, the excitatory arc admits of being in part formed of those substances which are the proper components of the animal arc.

5. The energies of both the excitatory and the animal arcs are alike suspended by the separation of their component parts, or at least by the separation of these parts to a certain distance.

6. Even the smallest degree of moisture is sufficient to

(c) We do not think it has ever been proved, that one piece of metal, or several pieces of the same metal, are capable of forming the excitatory arc. It is admitted on all hands, that the slightest alloy communicates galvanic energy to a piece of metal; that is, renders it capable of forming the excitatory arc. It is also known, that metallic oxyds are much less perfect conductors of galvanism than their corresponding regula, to make use of an antiquated expression. It appears to us, that in all cases where one metal appears to act, more especially where friction with the fingers, or breathing on a piece of metal formerly inert, give it galvanic powers; in all these cases, we think it probable that a slight degree of oxidation, produced in some part of the surface of the metal, gives it activity by destroying the homogeneity of its nature. We do not find that this circumstance has been in general sufficiently attended to. Dr Wells having discovered that charcoal acts powerfully as an exciter when applied along with a metal, found that by friction it also can be rendered capable of acting singly. What change is thus produced in it we can only conjecture; but that it is something which destroys the identity of its structure, rendering it in some measure a heterogeneous substance, must be admitted.

Candour forces us to acknowledge, that in one of M. Humboldt's experiments, it seems very difficult to point out any want of homogeneity in the exciting arc. He put into a china cup some mercury exactly purified; he placed the whole near a warm stove, in order that the entire mass might assume an equal temperature; the surface was clear, without the appearance of oxidation, humidity, or dust. A thigh of a frog, prepared in such a manner that a crural nerve and a bundle of muscular fibres of the same length hung down separately, was suspended by two silk threads above the mercury. When the nerve alone touched the surface of the metal, no irritation was manifested; but as soon as the muscular bundle and the nerve touched the mercury together, they fell into convulsions so brisk, that the skin was extended as in an attack of tetanus. This is by far the most decisive experiment which has been tried on the same side of the question; but as it must be admitted, that in most cases two metals are absolutely necessary, and that a single metal often derives activity from circumstances so slight, that we could not a priori have expected that they were capable of producing any change; we feel ourselves compelled to conclude, that in M. Humboldt's experiment some similar very slight circumstance had escaped unobserved; perhaps some gilding, or ornaments with metallic colours, in a state of oxidation. to join the parts of the excitatory arc, and to determine their effects upon the animal arc.

7. The influence of the state of the atmosphere, and of surrounding circumstances, upon the success of the experiments of galvanism, is, consequently, very great. In order, therefore, to perform these experiments with due accuracy, the state of the hygrometer, and of other meteorological instruments, must be vigilantly inspected during their progress; and the influence of the persons making the experiment upon the sphere within which it is made, must likewise be carefully attended to.

8. The experiments which were made to ascertain the nature of the animal arc, together with those made upon the excitatory arc, with a view to the comparison of the effects of the flesh of animals, with or without the epidermis, and of the different effects of this epidermis, when it is wet and when it is dry, appear to suggest to us, that the epidermis is one of those substances which diminish or interrupt the efficacy of the excitatory arc. The epidermis is, as well as the hairs and brittle parts of animal bodies, among the number of those substances which deserve the appellation of idiocentric.

9. Examine the substances which are fit for the formation of the excitatory arc, and you will find that the greater part of those which have been successfully put to this use are substances capable of acting as conductors of the electrical fluid; but that the substances which interrupt the operation of galvanism are generally such as are well known also to reflect the transmission of electricity.

10. Lastly, it appears, that the galvanic energy depends, not only upon the nature and arrangement of the component parts of the excitatory arc, but on their extent too, and on the magnitudes of their transmitting surfaces.

III. The committee appear to have used no less care and discernment in experiments upon those circumstances, which, though different from the structure of the galvanic circle and its two constituent arcs, have, however, a decisive influence upon the exhibition of the phenomena of galvanism. Some curious observations were made on the differences in the state of the parts exposed to the galvanic action. It was ascertained, that frogs fresh from the ditches did by no means exhibit the same phenomena as those which had been during some days preserved in the house; nor did the limbs of animals, when recently stripped of the skin, present the same appearances as after they had been subjected to a variety of galvanic experiments; nor were the same effects to be produced upon the parts of animal bodies which, after a certain number of trials, had been left for a while at rest, and then taken up again, as upon those which had been subjected to one continued train of experiments. The committee next examined the variations in the success of the experiments upon a strong lively frog, which may be produced by varying the mode in which the communicator is carried from the one supporter to the other: when the communicator is brought into contact with the supporter, or is withdrawn from actual contact with it; when the communicator is brought slowly, or when it is brought rapidly, into contact with the supporter; the effects are nearly the same: and a smart convulsion is, in all these cases, produced at the moment of the commencement of the mutual contact, or of its cessation. But when the frog is fatigued, the effects are different. These successive experiments likewise affect the results of one another, by means even of their succession solely. And they are also naturally subject to be influenced by the nature of the media amidst which they are performed; such as common air, water, an electrical atmosphere. The following are the inferences which have been deduced from this class of these experiments.

1. In many cases the galvanic energy is excited by exercise, is exhausted by continued motion, is renovated by rest.

2. The multiplicity of the causes by which the experiments of galvanism are liable to be influenced to success or failure, is so great, that we cannot, as yet, be too cautious in either rejecting or believing the accounts which we hear of the success of any such experiments; unless when we are able accurately to appreciate all the influencing circumstances.

3. This is remarkably confirmed by a fact, which the committee have related in their paper, and which respects the continuation of the galvanic pain. The communicator being supported by the hand, and resting, seemingly, without change of position, still upon the same point of contact, there is known to take place a real change in the galvanic contact, although the communicator have remained thus apparently motionless.

From this, it may be farther inferred, that the smallest possible change in the relative situations of the parts of the galvanic circle and the excitatory arc, is capable of producing an effect upon the susceptible animal, and of occasioning mistakes in regard to the success of the experiment, if the utmost care be not taken to notice and eliminate every variation that can happen.

4. The truth of the foregoing proposition is further confirmed by the experiments upon the manner in which the galvanic movements are affected by the advancing or the withdrawing of the communicator. For these experiments fully evince the necessity for the most vigilant observation of every movement in the process of an experiment, not only collectively, but in their succession, and at the different periods of the operation.

5. It should seem that there are, in the formation of the excitatory arc, independently of its modes of acting in the galvanic operations, certain enervating, and certain exciting dispositions; of which some not only augment or diminish the energy in the present instance, but, besides, dispose the animal to a greater or a smaller susceptibility, under subsequent experiments.

6. In order to accuracy of experiment, and to the correct ascertaining of the effects of an experiment, it is of great importance to know the precise state of the animal, the manner in which it has been preserved and sustained to the present moment, the state of the atmosphere, particularly as it is indicated by the hygrometer, by the barometer, the thermometer, and the electrometer.

7. It were to be wished, that in making a statement of experiments of different sorts, these should be arranged in the order of their efficacy, and that there might thus be formed a galvanic scale, which should help us to determine the precise degree of the galvanic susceptibility. susceptibility of any animal in this or that particular state or position, should direct us in subjecting every such animal only to experiments suitable to its particular susceptibility; should enable us to estimate, from the efficacy or inefficacy of our experiments, the galvanic value of the circumstances in which we every day find ourselves, and should enable us to judge when the success or miscarriage of an experiment can afford room for certain conclusions absolutely negative or affirmative.

IV. In their experiments upon the means of varying, diminishing, and renewing the susceptibility of animal bodies to the influence of galvanism, the committee examined, 1st, the influence of electricity upon that susceptibility; 2d, the effects of the muscular organs, and of certain liquors, such as alcohol, the oxygenated muriatic acid, the solutions of potash and opium, upon the galvanic properties; 3d, and at the medical school of Paris they made a number of experiments, in order to ascertain what new modifications the galvanic energy undergoes in various cases of suffocation or asphyxia. These last-mentioned experiments were made upon hot-blooded animals, of which some were reduced into the state of asphyxia by submersion, some by strangulation, some by the action of gases, while others were killed in vacuo by the discharge of the electric spark. In that suffocation which was produced by sulphurated hydrogenous gas, by carbonic vapours, and by submersion, in which the animal was suspended by the hinder feet, the galvanic susceptibility was entirely destroyed. The galvanic susceptibility was only suspended by suffocation produced by the pure carbonic acid confined under mercury. It was diminished, but not destroyed, in those cases of suffocation, which were occasioned by sulphurated hydrogenous gas that had lost a portion of its sulphur, by gas ammoniae, gas azote, or such gases as had been exhausted of their pure air by respiration; and the same thing was found to take place in animals which had perished by total submersion. But the galvanic susceptibility survived unaltered in suffocations brought on by submersion in mercury, by pure hydrogenous gas, by carbonated hydrogenous gas, by oxygenated muriatic acid, by sulphureous acid; as also when the suffocation was occasioned by strangulation, by the abstraction of the air in the air-pump, or by discharges from an electrical battery. The results of the experiments at the medical school suggested the following reflections:

1. Though it be true that all cases of suffocation resemble one another in the privation of respirable air, and in the suspension of the functions of respiration, and of the circulation of the blood; yet, in their other circumstances, they are subject to great differences, arising from diversity of nature in the substances by which they are occasioned.

2. Of these causes, some appear to act with a more thorough efficacy, penetrating at once all parts of the nervous and muscular systems. Others again seem to act but superficially, producing only pulmonary asphyxia, with its immediate effects.

Suppl. Vol. I. Part II.

3. One of the most remarkable changes not confined to the organs of respiration, consists in the alterations produced on the galvanic susceptibility. In that respect the various cases of asphyxia differ greatly one from another.

4. The state of the irritability of the muscles, when examined by means of bodies, the mechanical action of which causes the muscles to contract by irritating them, is far from always corresponding to the state of their galvanic susceptibility.

5. Lastly, the causes of suffocation or asphyxia, do not act upon all parts of the muscular system in the same manner; but the heart is very often found in a state extremely different from that of the other muscles.

V. The comparison between the phenomena of galvanism and those of electricity is perhaps one of the most interesting objects of attention in the whole body of a-phenomena of animal physiology. It is well known that Galvani was accidentally led to his discovery by observing the motions of some frogs, at a certain distance from an electrical machine discharging sparks. The committee from the institute made, therefore, some attempts to ascertain the relations between electricity and galvanism. Having first paid due attention to the susceptibility of animals toward the influence of electricity, they then sought to discover to what precise degree animals deprived of the natural covering of the epidermis were liable to be affected by the variations of the electrical fluid in the atmosphere around them. Next, comparing the susceptibility of electricity with the susceptibility of galvanism, they perceived that quantities of the electrical fluid, such as are still capable of being very accurately measured by the electrometer, are, however, often too weak to act upon a frog that retains the most perfect sensibility to all the energy of galvanism. The members of the committee purpose to prosecute farther their experiments upon this part of the subject.

VI. The following are the general results of the experiments made by M. Humboldt in the presence of some experiments by Humboldt:

1. There is no truth in the assertion of certain physiologists, that the experiments of galvanism fail when tried upon the heart and those other muscles of which the contractions depend not upon volition; for these organs have been found to be actually subject to the influence of galvanism (n).

2. The effects of galvanism are liable to be interrupted by the constriction of a nerve, whenever both the nerve and the constricting ligature are enveloped in the flesh of the animal body (e).

3. The powers of the exciting arc may be renovated or destroyed, even though its supporters remain the same, and although the extremities of the arc be unchanged. Only the relations of the intermediate matters require to be altered.

4. There are atmospheres of galvanism.

5. There are substances which, though in an eminent manner conductors of electricity, yet interrupt the motions of galvanism.

M. Humboldt had performed also other experiments, which,

(d) This was demonstrated six years ago by Dr Fowler. (z) Dr Valli made this observation soon after the discovery of galvanism. which, when he attempted to repeat them before the committee, could not be brought to succeed, on account, as was supposed, of the season of the year.

Such are the principal results of this valuable train of experiments upon galvanism. From them, our readers will perceive that this interesting subject is still very imperfectly understood, and will form some idea of the importance of the discoveries which a diligent prosecution of it promises to the philosopher and the physician.

The effects of galvanism upon some of the organs of sense are no less striking than those which we have seen capable of producing upon the muscles.

If the upper and under surfaces of the tongue be coated with two different metals, and these be brought into contact with each other, a peculiar sensation, resembling taste, is produced in the tongue the moment that the metals touch each other. With the greater number of metals this sensation is scarcely perceptible; but with zinc and gold, zinc and silver, or zinc and molybdenum, it is very strong and disagreeable. Dr. Fowler thinks it is strongest with zinc and gold; to us it appears a good deal stronger with zinc and silver. It is sensibly stronger when the zinc is applied to the upper, and the silver to the under surface of the tongue, than when this order is inverted. The sensation is most distinct when the tongue is of the ordinary temperature, and the metals of the same temperature with the tongue. Any considerable increase or diminution of heat in either greatly lessens the effect. Mr. Sibbitt of Berlin, in his "Théorie des Plaisirs," p. 155 (published in 1767), takes notice of the disagreeable taste produced by silver and lead in contact upon the tongue. This is the first instance of galvanism that has been made public.

To ensure complete success to the experiment, the metals ought to be allowed to remain some time in contact with the tongue before they are made to touch each other, that the taste of the metals themselves may not be confounded with the sensation produced by their mere contact. Whatever has a tendency to blunt the sensibility of the tongue, as opium, alcohol, acids, and the like, diminishes the effect of the metals.

It is difficult to describe the sensation thus produced accurately. It has been called "subacid;" but we think it more nearly resembles the effect produced by allowing a grain or two of nitre to lie upon the tongue for some time, than any other taste with which we are acquainted. Joined to this, there is evidently a metallic taste, which varies with the metal employed; but we are inclined to consider this as the ordinary effect of the metals upon the tongue, which cannot be perfectly distinguished from that occasioned by their mutual contact.

This taste can also be produced by applying one of the metals to the tongue, and the other to any part of the Schneiderian membrane. Professor Robison has made many experiments of this kind, the result of which is contained in a letter to Dr. Fowler. "I find (says he), that if a piece of zinc be applied to the tongue, and be in contact with a piece of silver which touches any part of the lining of the mouth, nostrils, ear, urethra, or anus, the sensation resembling taste is felt on the tongue. If the experiment be inverted, by applying the silver to the tongue, the irritation produced by the zinc is not sensible, except in the mouth and the urethra, and is very slight. I find the irritation by the zinc strongest when the contact is very slight, and confined to a narrow space, and when the contact of the silver is very extensive, as when the tongue is applied to the cavity of a silver spoon. When the zinc touches in an extensive surface, the irritation produced by a narrow contact of the silver is very distinct, especially on the upper side of the tongue, and along its margin. This irritation seems to be a mere pungency, without any resemblance to taste, and it leaves a lasting impression like that made by caustic alkali.

"When a rod of zinc, and one of silver, are applied to the roof of the mouth, as far back as possible, the irritations produced by bringing their outer ends into contact are very strong, and that by the zinc resembles taste in the same manner as when applied to the tongue."

M. Volta found, that when a tin cup, filled with an alkaline liquor, is held in one or both hands, previously moistened with water, if the point of the tongue is dipped in the liquor, an acid taste is perceived. This is at first distinct and pretty strong, but gradually yields to the alkaline taste of the liquor. The acid taste is still more remarkable, when, instead of an alkaline liquor, an insipid mucilage is made use of. The same philosopher found, that when a cup made of tin, or what is better, of zinc, was filled with water, and placed upon a silver support, if the point of the tongue was applied to the water, it was found quite insipid, till he laid hold of the silver support, with the hand well moistened, when a very distinct and very strong acid taste was immediately perceived.

If one of the metals be applied to the tongue, and the other to the ball of the eye, a pale luminous flash is perceived when they are brought into contact with each other, and the sensation resembling taste is at the same time produced in the tongue. A flash is, in like manner, produced when one of the metals is applied to the eye, and the other to any part of the palate, fauces, or inside of the cheek. This experiment requires a good deal of attention in the performance; care must be taken not to press the piece of metal against the ball of the eye, lest a flash should be produced by the mere mechanical pressure. It should be cautiously introduced between the eye-lids, till it just touch any part of the ball; and it should be allowed to remain in that situation for some time before it is brought into contact with the other piece of metal, that the parts may be so far accustomed to it as to admit of the sensations produced being properly attended to. The experiment succeeds very well with tin and silver; but the flash is more bright when zinc and gold are used. The piece of metal which is applied to the ball of the eye must be finely polished, otherwise the mechanical irritation is sometimes so great as to prevent the flash from being perceived. Dr. Robison has observed, that the brightness of the flash corresponds with the extent of contact of the metal with the tongue, palate, fauces, or cheek.

If a piece of one of the metals be placed as high up as possible between the gums and the upper lip, and the other in a similar situation with respect to the under lip, a very vivid flash of light is observed at the moment that they are brought into contact, and another at the instant of their separation. While they remain in contact, no flash is observed.

When a rod of silver is thrust as far as possible up one of the nostrils, and then brought into contact with a piece of zinc placed upon the tongue, a very strong flash of light is produced in the corresponding eye at the instant of contact. We have sometimes imagined, that the flash in this experiment was produced before the metals actually touched; but in this we may have been deceived.

The following curious experiment was first made by Professor Robison: "Put a plate of zinc into one cheek, and a plate of silver (a crown piece) into the other, at a little distance from each other. Apply the cheeks to them as extensively as possible. Thrust in a rod of zinc between the zinc and the cheek, and a rod of silver between the silver and the other cheek. Bring their outer ends slowly into contact, and a smart convulsive twitch will be felt in the parts of the gums situated between them, accompanied by bright flashes in the eyes. And these will be distinctly perceived before contact, and a second time on separating the ends of the rods, or when they have again attained what may be called the striking distance. If the rods be alternated, no effect whatever is produced."—The flashes produced in this last experiment are rather more vivid than any which we have been able to excite by the other methods. The convulsive twitches are very distinct, and somewhat painful, but quite different from the sensation produced by an electric shock. If the edges of the tongue be allowed to touch the plates of metal in the cheeks, the sensation resembling taste is felt very strongly; but this does not in the least impair the other effects of the experiment.

No method has yet, we believe, been discovered of applying the galvanic influence so as to affect the senses of smelling or hearing. We have tried many experiments with this view, chiefly on the organs of smelling; but hitherto without any success. Neither has the sense of touch been affected by it, unless, indeed, the following experiment be considered in that view: Let a small portion of the cuticle be removed from any part of the body by a sharp knife, and carry the incision to such a depth that the blood shall just begin to ooze from the cutis vera. Let a piece of zinc be applied here, and a piece of silver to the tongue; when they are brought into contact, a very smart irritation will be felt at the wound.

Some very singular facts of this kind have been discovered by M. Humboldt, who had the resolution to make himself the subject of many well-devised experiments. One of the most remarkable of these is the following: He caused two blistering plasters to be applied on the deltoid muscle of both his own shoulders. When the left blister was opened, a liquor flowed out, which left no other appearance on the skin than a slight varnish, which disappeared by washing. The wound was afterwards left to dry up; this precaution was necessary, in order that the acrid humour which the galvanic irritation would produce, might not be attributed to the idiosyncrasies of the vessels. This painful operation was scarcely commenced on the wound, by the application of zinc and silver, before the serous humour was discharged in abundance; its colour became visibly dark in a few seconds, and left on the parts of the skin where it palled traces of a brown inflamed red. This humour having descended towards the pit of the stomach, and flopped there, caused a redness of more than an inch in surface. The humour, when traced along the epidermis, left stains, which, after having been washed, appeared of a bluish red. The inflamed places having been imprudently washed with cold water, increased so much in colour and extent, that M. Humboldt, as well as his physician Dr Schalleru, who assisted at these experiments, entertained some apprehension for the consequences.

Having now taken notice of the principal facts that are hitherto known in galvanism, we proceed to consider some of the leading opinions on the subject.

The first writers upon the discovery of Galvani seem almost universally to have taken it for granted, that the phenomena depend on the electric fluid; and leaving this most important question behind them, proceeded to explain how this fluid produces such effects. The celebrated discoverer of this influence himself considers a muscle as the perfect prototype of a Leyden phial. When a muscle contracts upon a connection being formed, by means of one or more metals between its external surface and the nerve which penetrates it, M. Galvani contends, that, previously to this effect, the inner and outer parts of the muscle contain different quantities of the electric fluid; that the nerve is consequently in the same state, with respect to that fluid, as the internal substance of the muscle; and that, upon the application of one or more metals between its outer surface and the nerve, an electrical discharge takes place, which is the cause of the contraction of the muscle. Thus the nerve is supposed to perform the office of the wire connected with the internal surface of the phial; and the excitatory arc is considered merely as a conductor.

This theory appears to us just as incapable of explaining the phenomena of galvanism as it is inconsistent with the known laws which regulate the motions of the electric fluid. We shall not consider it minutely; for we hope it will soon appear highly probable, if not certain, that the electric fluid has no share in the production of the phenomena in question. If this be the case, all the different modifications of that theory must of course fall to the ground. At present we shall content ourselves with asking the following questions:

1. How is it possible for the electric fluid to be conducted in a muscle, which is wholly surrounded by substances capable of conducting that fluid? 2. If we suppose there is some non-descript non-conducting substance placed between the external and internal surfaces of the muscle, how can it be possible for the electric fluid to be conducted through it?

(r) Professor Robison has long ago observed, that the flavour of a pinch of snuff taken from a box made of tin-plate, which has been long in use, so that the tin coating is removed in many places, is extremely different from that of snuff when taken from a new box, or a box lined with tinfoil. The same difference is observed when we rub a piece of pure tin, or of pure iron and a half worn tinned plate, with the finger. Also, if we rub a cast steel razor, and a common table knife consisting of iron and steel welded together. This is surely owing to a cause of the same kind. ternal parts of a muscle, which may admit of the one being positively, and the other negatively electrified at the same time; how comes it to pass that a discharge does not take place, and a consequent contraction ensue, when any substance whatever, capable of conducting the electric fluid, is interposed between the nerve and the external surface of the muscle? For example, when the nerve and muscle are laid bare, and the animal thrown into water; or when the nerve is cut through, and the end applied to the external surface of the muscles.

3. How does it happen, when one discharge actually takes place, in consequence of the application of the excitatory arc, that the balance is not instantly restored? That this does not happen, appears by the same muscle and nerve being capable of producing many hundreds of similar, and equally strong discharges, without any apparent means of the equilibrium being again disturbed.

We have never seen any answers to these questions which appeared to us at all satisfactory; and till we have seen them answered, we must be excused for disbelieving M. Galvani's theory.

One of the earliest writers, and one of the most assiduous investigators of the phenomena of galvanism, is Dr Valli. He differs in opinion from Galvani upon several points; but agrees with him in thinking electricity and galvanism the same. Let us consider the proofs by which he supports this doctrine.

"I have asserted (says he), that the nervous fluid is the same with electricity, and with good reason; for substances which conduct electricity are conductors likewise of the nervous fluid.

"Substances which are not conductors of electricity do not conduct the nervous fluid.

"Non-conducting bodies, which acquire by heat the property of conducting electricity, preserve it likewise for the nervous fluid.

"Cold, at a certain degree, renders water a non-conductor of electricity as well as of the nervous fluid.

"The velocity of the nervous fluid is, as far as we can calculate, the same with that of electricity.

"The obstacles which the nerves, under certain circumstances, oppose to electricity, they present likewise to the nervous fluid.

"Attraction is a property of the electric fluid, and this attraction has been discovered in the nervous fluid.

"We here see the greatest analogy between these fluids; nay, I may even add, the characters of their identity."

That there is a considerable analogy between some of the effects of the electric fluid and some of the phenomena of galvanism, we readily admit; but that "the characters of their identity" are anywhere to be found, we absolutely deny. In the above passage, Dr Valli considers it as certain, that the nervous fluid is the cause of the phenomena discovered by Galvani. But it has never been demonstrated irrefragably, that any such thing as a nervous fluid exists, and still less that this is the same with the influence discovered by Galvani.

That bodies are, in general, conductors or non-conductors of galvanism, according as they are conductors or non-conductors of electricity, we believe to be true; but this rule is by no means without exception, as it certainly would be, if galvanism and electricity were the same. There is an experiment of Dr Fowler's, which seems to show, that water is a more powerful conductor of galvanism than mercury; though the reverse is generally allowed as to electricity.

If the abdomen of a frog be filled with water, and a silver probe passed through it so as to touch the fleshy nerves, no contractions are produced; neither do they appear when the probe is touched above the surface of the water with a piece of zinc. But if the zinc be applied to the probe at the surface of the water, contractions are produced as vigorous as if both the metals touched the nerve. Here the water serves as a conducting medium between the nerves and the point where the metals touch each other; but if the abdomen be filled with mercury instead of water, no contractions are produced by applying the silver probe to the nerves, and touching the probe with the zinc at the surface of the mercury. We do not see how this experiment can be accounted for, except by allowing that water is a more powerful conductor of galvanism than mercury.

If this experiment should be thought inconclusive, we have the authority of M. Humboldt, and of the committee of the National Institute of France, for saying, that there are substances which, though in an eminent manner conductors of electricity, yet interrupt the motions of galvanism. This is certainly sufficient to take away all weight from Dr Valli's two first reasons for considering these two fluids as the same, viz. that all conductors of electricity are likewise conductors of galvanism; and that all bodies which do not conduct the former are also non-conductors of the latter. These two are by far the most important of his reasons; and if they were true in their full extent, they would certainly show a very striking analogy, though they would by no means deserve the appellation of "characters of identity."

As to the Doctor's two next propositions, which regard the effects of heat and cold in rendering bodies conductors or non-conductors, they are, in fact, only branches of the two first; and as we have seen that these are not universally true, we might admit that they are correct in this particular, without weakening our argument. For this reason we shall not consider them minutely; but we may observe that Dr Fowler's experiments show, that boiling water, and water cooled down to the freezing point, both conduct this influence as well as water at the ordinary temperature of the atmosphere. If any change in the conducting power takes place beyond these points, it may with greater probability be ascribed to the changes of form which the water undergoes, than to the increase or diminution of its temperature.

We confess ourselves perfectly ignorant of any data upon which Dr Valli could found a calculation, the result of which could show that the velocity of the nervous fluid is the same with that of electricity. Suppose we should take it into our heads to assert that the velocity of galvanism is the same with that of light, we apprehend our author could not easily demonstrate the contrary. Neither, in all probability, would he consider this assertion of ours as a sufficient proof that galvanism and light are the same.

With regard to the next proposition, that "the obstacles which the nerves, under certain circumstances, oppose to electricity, they present likewise to the nervous fluid," we may remark, that any obstacle which destroys destroys the functions of a nerve completely, will prevent the muscles which are supplied by that nerve from contracting upon the application of any stimulus whatever (g). It does not, however, by any means follow, that the passage of either the galvanic or the electric fluid is prevented. The nerves may still be very good conductors of both, though the muscle is deprived of all power of contracting. That there are obstructions, however, which the nerves, under certain circumstances, present to the passage of electricity, but which they do not under the same circumstances present to galvanism, we think abundantly demonstrated by Dr Valli's own experiments.

"I have frequently observed (says he) that the legs, of which the nerves had been tied at a certain distance from the muscles, did not feel the action of a certain quantity of artificial electricity, although they were violently convulsed by exciting that which was inherent and peculiar to them." What then was the cause of the difference observed in these cases between the effects of galvanism and electricity? Was it, that the quantity or degree of the former exceeded that of the latter? Be it so.

Dr Valli informs us, that in his experiments, an electric charge which could pass through a thickness of air equal to .035 of an inch, produced no movement in the leg of a frog of which the crural nerve was tied, while the other leg, of which the nerve was left free, underwent considerable movements.

That the influence discovered by Galvani can pass through an exceedingly thin plate of air, is certain, as it is transmitted from link to link of a chain, where no considerable force is used to bring the links into contact. Dr Robison's experiment, too, in which the flashes of light are distinctly observed before the rods of silver and zinc touch each other, is another proof of the same fact; and, if we be not deceived, the same thing takes place when a rod of silver thrust up the nostril is applied to a piece of zinc in contact with the tongue. But that it will only pass through an exceedingly thin plate of air, any man may convince himself by an experiment, first tried by Dr Fowler, which is easily repeated. If a flake of sealing wax be coated with tinfoil, it will be found a very good conductor; but if, with a sharp pen knife, an almost imperceptible division be made across the tinfoil, even this interruption of continuity in the conductor will be found sufficient effectually to bar the passage of galvanism.

We find, then, that a quantity of the electric fluid which can pass through a plate of air of the thickness of .035 of an inch, is obstructed by a ligature upon a nerve, while the galvanic influence passes readily along a nerve included in a ligature, but is obstructed completely by making an almost imperceptible division in a good conductor. The plate of air in this case surely is not near .035 of an inch in thickness. It results incontrovertibly, from a comparison of these two experiments, that there is, between these two agents, some other difference besides the mere degree of intensity.

We come now to the last reason which our author assigns for his belief that galvanism, or, as he chooses to call it, the nervous fluid, is the same with electricity. It will be found a very important one. That property by which bodies charged with the electric fluid attract or repel other bodies, according as they are in the same or the opposite state of electricity from themselves, is so striking, and at the same time so universal, that it has been very properly adopted as the measure of this fluid. If it were true, then, that the galvanic influence possessed the same properties of attraction and repulsion as the electric fluid, this circumstance would certainly increase the analogy between them very much. As we have already seen, however, that they differ in other essential points, even if it were true that they agreed in this, it could constitute no proof of their identity. But if, on the other hand, we should find, that this assertion of our author is founded on error, and that the galvanic influence possesses in no degree whatever those properties of attraction and repulsion which have always been justly considered as essential characteristics of the electric fluid, we shall then be fully justified in affirming, that these two agents, however much they may resemble each other in some less important particulars, are in their nature totally distinct and unconnected.

Let us examine the proofs by which Dr Valli's assertion is supported. He tells us, that he observed the hair of a mouse, attached to the nerves of frogs, by means of the tinfoil with which he surrounded them, alternately attracted and repelled by each other, whenever another metal was so applied as to excite contractions in the frogs. We are very far from meaning to infirmate that Dr Valli did not see, or think he saw, what he thus describes; but that the motion of the hairs must have arisen from some cause, different from that to which he ascribed it, cannot admit of a doubt; for hairs, in such a state of electricity as he supposes, never attract, but always repel each other.

Dr Fowler, who has paid particular attention to this part of his subject, has many times repeated this experiment, both in the manner described by Dr Valli and with every variation in the disposition of the hairs which he could devise: but whether they were placed on the metals, the nerves, or the muscles, or upon all at the same time, he has never in any instance been able to observe them agitated in the slightest degree. He has made similar experiments upon a dog, and upon a large and lively skate, by dipping, in the same way that Valli did the hairs of a mouse, flakes of the finest flax, swan-down, and gold leaf; but although the contractions produced in the skate, by the contact of the metals, were so strong as to make the animal bound from the table, not the least appearance of electricity was indicated. He next suspended from a flake of glass fixed in the ceiling of a close room, some threads, five feet in length, of the flax used in the former experiment; and brought some frogs recently killed, and immersed upon glass, as near to them as possible without touching; but the threads were in no wise affected by the contractions produced in the frogs.

In a very ingenious paper upon galvanism by Dr Wells,

(g) We do not here mean that contraction which muscles are susceptible of long after death, upon having their fibres mechanically irritated, which is produced by what physiologists have called the vis insita, and which is perfectly known to our cooks, as it was to their predecessors in the Roman kitchens, as the foundation of the art of crimping. We at present confine ourselves to contraction produced through the medium of the nerves. Wells, which is published in the London Philosophical Transactions for 1795, that gentleman maintains the opinion, that the influence discovered by Galvani is electrical. He admits, that it is not attended with those appearances of attraction and repulsion which are held to be the tests of the presence of electricity; but he contends, that "neither ought signs of attraction and repulsion to be in this case presented on the supposition that the influence is electrical; since it is necessary, for the exhibition of such appearances, that bodies, after becoming electrical, should remain so during some sensible portion of time; it being well known, for example, that the passage of the charge of a Leyden phial, from one of its surfaces to the other, does not affect the most delicate electrometer, suspended from a wire, or other substance, which forms the communication between them."

That the charge of a Leyden phial does not, in passing along a wire, affect an electrometer, is certain; and it is equally true, that we have no means of applying an electrometer to a quantity of galvanism in a state of rest in a body. If this influence ever exists in such a state, we have no test by which we can discover its presence; and it is only from the effects which it produces in transitu that we know of its existence. But the electric fluid, in passing from link to link of a chain, sensibly affects an electrometer; and in Dr Fowler's experiment with the skate, for example, as more than one piece of metal is employed as an exciter, the fluid, in passing from one piece to another, should have affected the light substances which were placed upon them. This appears to us a sufficient answer to the objection started by Dr Wells; but the same objection having been lately made to us by a gentleman from whom we shall always receive every suggestion with uncommon deference, we thought it worth while to try the following experiment:

Three hours after a frog had been decapitated, it showed strong signs of galvanic susceptibility. One of the sciatic nerves being coated with tinfoil in the usual manner, the leg was laid upon a plate of zinc. A gentleman was desired to lay hold of the nerve and its coating with the fingers of one hand, which had been previously dipped in water, while with the other hand, also wet, he held the end of a small brafs chain about two inches in length. Another gentleman now took hold of the other end of the chain, and with a silver probe, held in his other hand, touched the plate of zinc. The influence being thus made to pass through the chain, the leg contracted vigorously; but a very sensible electrometer, held so near to the chain as almost to touch it, was neither attracted nor repelled. In performing this experiment, it was necessary to have the hands wet, as the dry cuticle tends much to obstruct the passage of galvanism; but the utmost care was taken that the chain should be perfectly dry, otherwise the influence might have been transmitted by the moisture upon its surface without passing through the chain itself.

To avoid the possibility of this happening, the experiment was varied in the following manner: The frog's leg was laid upon a plate of zinc, and the nerve upon a plate of silver. A gentleman now took a silver probe, and one end of the brafs chain in contact with it, in one hand; and in the other hand he held the other end of the chain in contact with a rod of zinc. He now touched the silver plate with the rod of silver, and the zinc plate with the rod of zinc. As the influence was not now to be made to pass through his body, there was no necessity for his hands being wet; the whole excitatory arc was therefore made completely dry. In this way very strong contractions were excited in the leg, and still the electrometer was not affected in the smallest degree when brought near the chain.

It is proper to observe, that Dr Valli, in his assertion that attraction is a property of galvanism, does not rest entirely upon his own observation; a committee of the Academy of Sciences at Paris performed the following experiment along with him: "They placed a prepared frog in a vessel which contained the electrometer of M. Coulomb, charged negatively and positively by turns. In both cases, in exciting the animal in the common way, the ball of the electrometer was attracted." It appears to us that Dr Valli and the committee have been deceived, by the friction produced by the motion of the animals under their experiments having excited too much electricity as to affect the electrometer. The first time we tried the experiment abovementioned with the brafs chain, we were almost misled by a similar circumstance. Instead of an artificial electrometer, which we happened not to have at hand, we made use of a very long and slender human hair; and we found that it was strongly attracted by the chain. Upon an attentive examination, however, we found that this did not arise from the action of the influence passing through the chain, but from the state of the hair itself, which was so highly electrical as to be strongly attracted by every conducting substance which it approached. Upon substituting another hair, which showed no mark of being either positively or negatively electrified, it was neither attracted nor repelled by the chain. From the above, or some similar circumstance, it is probable that Dr Valli's mistake has originated; but we are confident, that whoever will repeat the experiment with sufficient attention, will find the result precisely as we have described it.

Perhaps it may still be said, that although we have never been able to discover attraction and repulsion as properties of galvanism, this may arise from our not being able to accumulate this influence in sufficient quantity. To this reasoning, if reasoning it can be called, we oppose the following considerations, which state a dissimilarity in the phenomena of electricity and the galvanism, that seems absolutely irreconcilable with the identity of the cause.

Nothing is more completely established in the science of electricity than this, that all those appearances which fail not to call attractions, repulsions, affinities, and accumulations of electric fluid, are precisely similar to what would take place if electricity were a fluid, whose particles repel each other, and attract the particles of other matter, according to a certain law (See Electricity, Suppl.). Of all those phenomena, the most remarkable is the accumulation of electric energy (to give it no more definite name), by means of thin idio-electrics, coated with non-electrics; such, namely, as are exhibited by the Leyden phial, the condenser, the doubler, &c.

If the phenomena of galvanism are produced by the passage of electric fluid from one extremity of the excitatory arc to the other, this passage will be regulated by the known laws of electricity. It may therefore be accumulated... accumulated (in transitu) by means of an apparatus similar to the coated pane, or to the condenser. Professor Robison, with this view, made the following experiments:

1. He made a part of the conductor to his condenser, or collector of atmospheric electricity, consist of a long glass rod, on one side of which was fastened (with varnish) a very narrow slip of tin foil; there was a fine point at one end of this rod, and a gold leaf electrometer at the other. This apparatus was insulated at one end of a room 10 feet long, having a window in the middle of each side. A small electric machine was placed at the other end. On a dry day, with a gentle breeze in a direction across the room, both windows were opened a little way, so that there was a continual stream of air across the room. The machine was worked; and after a short time had elapsed, the electrometer began to diverge, gradually opened, and at last struck the conducting slips on each side, and then collapsed, and again began to diverge. The windows were shut; and immediately, without working the machine, the electrometer diverged rapidly, and touched the sides of the panes every minute and half. This continued so long, that there seemed to be no end to it. The Professor now made a cut across the tin foil with a very sharp knife; the electrometer now diverged very feebly, and 7½ minutes elapsed before it touched the sides. He pulled the knife a second time through the cut. This widened it (though scarcely sensible to the eye), because the knife had been blunted by the glass in the first operation. All divergency of the electrometer was now at an end; and although the machine was worked till the electric smell was sensible at the door to a person who happened to come in at this time, no tendency to divergence was observed. (N.B. the top of the electrometer had no conducting substance about it, except the slip of tin foil).

The cut, being examined with a microscope furnished with a micrometer, was 1/50th of an inch. It was now filled up, by binding over it another slip of tin foil. A plate of talc, whose thickness did not exceed the 600th of an inch, was coated on one side in a circle of 1½ inch diameter. The electrometer was removed, and the coated side of the talc was put into close contact with the slip of tin foil on the glass rod. A stand of tin, whose top was a plate of 1½ inch diameter, smeared over with mercury, was placed in contact with the other side of the talc, and they were pressed into very close and continuous contact.

The machine being now worked, the coated talc received a charge in about 5 minutes sufficient to give a very smart shock; and this was repeated with great regularity every five or six minutes. The windows were now thrown open, and the room cleared of its former contents of air, till none of those present could perceive any electric smell. The machine was now worked again. But after half an hour, only a very faint twitch was felt; but enough to show that an accumulation was taking place. The windows were now half shut. After working the machine about five minutes, a faint twitch was obtained; after a quarter of an hour more, there was a moderate shock.

In this state of things, the apparatus was examined as a condenser, by first taking out the sharp point by an inflating handle, and then removing the tin fland. Examined in this way, it appeared plainly that, even when all the windows were open, the accumulation began almost as soon as the machine was worked. Nay, it was found, on another day equally favourable, that a plate of talc 1/50th or 1/25th of an inch thick, took a charge, although a cut of 1/40th wide did not allow the electricity to fly across it. This is perfectly similar to all our experiments on coated glass. The thickness which admits an accumulation is almost incomparably greater than the distance to which a spark will fly, or a concussion is producible, in the same intensity of electricity.

2. The above described apparatus was insulated, and a wire connected with each end. To one wire was joined a thin plate of lac, coated on the side next the wire; and to the other a piece of moist leather covered with tin foil. These plates were rubbed together by means of inflating handles. The plate of coated talc quickly took a charge.

The same plate of talc, and afterwards another plate not more than half as thick, was now made part of the excitatory arc, and sometimes part of the animal arc. Sometimes plates of varnish, incomparably thinner than either of these, were employed. But all Professor Robison's attempts to produce an accumulation of galvanic energy in this way were fruitless. The second form of the electrical experiment was adopted, as having a somewhat greater resemblance to the supposed procedure of galvanism; but the well-informed electrician will easily perceive, that the first form is far more delicate and decisive.

The internal procedure in the electric and galvanic convulsions is therefore so different, nay, opposite, that we cannot bring ourselves to think that the appearances are operations of the same agent (n).

We have now gone over all the points of resemblance which, in Dr Valli's opinion, constitute the characters of the identity of galvanism and electricity. We think that, without going farther, we might safely rest our assertion, that these two agents are perfectly distinct and unconnected with each other. But there are several other circumstances which merit attention.

No electrical phenomenon can take place between two bodies, unless their bodies be in opposite states of conductivity with regard to each other. Now, how are we to account for the accumulation of electricity in any body, or part of a body, surrounded on all hands by non-conducting substances? The experiments of Galvani succeeded equally well, whether the subjects of them be insulated or surrounded by conductors; whether performed in the direct air or under water (i); whether, by means of an electrical machine, we charge the animal and the metals till every part of them strongly affect

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(n) What if it were called metallurgism, which translates exactly metallic irritation, or metallogerism, from metallurgia, and irritatio excitatio.

(i) Dr Fowler mentions an exception to this. "When the separated leg of a frog was held under water, and formed part of the circuit through which this influence had to pass in order to excite another leg, it never contracted; although it did, and strongly, when held above the surface." In this case it is plain, that the frog's leg... the electrometer, or whether we reverse the experiment and electrify them negatively, still no change is produced in the force or frequency of the actions excited by the application of the metals. Is there any electrical experiment which could continue to give the same result in such opposite circumstances? or is there any possibility of accounting for it consistently with the known laws of the electric fluid?

The writers on this subject who adopt the electric theory, instead of attempting to explain how the electric fluid can be condensed in a body surrounded by conducting substances, have recourse to the analogy of the gymnottus, torpedo, and other fishes of the same kind. Here, say they, we have in fact the electric fluid accumulated in such a situation, and there is no reasoning against facts. We answer, that these animals are all furnished with organs of a very peculiar structure, which may possibly be fitted for the purpose of such a condensation. Besides, we apprehend it has never been incontrovertibly proved that these singular animals derive their powers from the electric fluid. Without wishing to enter into this question, which is foreign to our present subject, we may remark, that Mr. Walsh discovered, that the shock of the torpedo would not pass through a small brass chain; a circumstance in which it differs remarkably both from electricity and from the influence discovered by Galvani.

It was worth while to try Professor Robison's methods of accumulation in the examination of the convulsions occasioned by the torpedo. The Professor suspects that the popular horror at the lamprey, and the accounts of cramps and pains produced by it, have their source in some similar powers of that animal.

Dr. Valli's reasoning on this part of the subject is very curious. He takes it for granted that the gymnottus owes its influence to the electric fluid. Then, though the gymnottus gives shocks and emits sparks, while the torpedo only gives shocks without emitting sparks, he says it would be absurd to assert that the torpedo derives its influence from a cause different from the gymnottus. Again, though the influence discovered by Galvani neither gives shocks nor emits sparks, it would still be absurd to maintain that it is not the same as the electric fluid, and as the influence of the gymnottus and torpedo. To dissent from any part of this very logical deduction, he declares would be contrary to the laws of philosophy itself! Rifum teneatis?

Afraid, probably, that his readers might be tempted to offend against these new laws, he proceeds to strengthen them by the analogy of animals and vegetables retaining an uniform temperature in media, warmer or colder than their own bodies; from which he argues that they may also have a power of accumulating electricity, and retaining it in a particular part, though their whole bodies are conductors. But the cases are in no respect similar. Neither animals nor vegetables accumulate caloric in any particular part of their bodies in preference to any other part. They have no power of retaining caloric in their bodies more strongly than any other bodies do; for if they are placed in a medium colder than themselves, they are continually imparting caloric to that medium. Neither is there the smallest proof, from any experiments yet published, that when placed in a medium warmer than themselves, they do not continually absorb caloric from it. The existence of a frigorific power in animals appears to us exceedingly problematical; but if it were proved to exist, it would by no means demonstrate that animals or vegetables have a faculty of declining to absorb caloric from bodies warmer than themselves. It is readily admitted, that animals and vegetables have a power, within certain limits, of preserving their temperature higher than that of the surrounding medium; nor is there any thing surprising in this, as the caloric, which they are continually receiving by the decomposition of oxygenous gas, is diffused slowly. But if we should allow that animals have a similar faculty of generating the electric fluid; from the nature of that fluid it must be continually communicated, not only to every part of the bodies of the animals themselves, the whole of which are conductors, but to every conducting substance contiguous to them; and this must take place, not slowly, like the diffusion of caloric, but instantaneously, so as to render any sensible accumulation impossible.

Galvanism differs from electricity in nothing more remarkably than in the mode of its excitement and diffusion. To produce the phenomena discovered by Galvani, no operation at all similar to the friction of an electric upon a conducting substance is necessary (1). The nerves and muscles have only to be laid bare, and a communication formed between them by means of the excitatory arc, when the contractions immediately ensue. In the case of electricity, a single discharge having restored the equilibrium, no further effects can be produced till this has been again destroyed by some means capable of producing a condensation in one quarter, and a comparative rarefaction in another. The fact is very different with regard to galvanism; for with it the number of shocks which may be given appears to be infinite. Nay, they frequently become stronger in proportion as they have been longer continued; this influence differing extremely in this particular, too, from the electric fluid, which, besides being itself exhausted, never fails in a remarkable manner to exhaust the contractile power of the muscles.

The permanence of the effects of galvanism is still more striking in the experiments upon the organ of taste. When the metals are applied to the tongue, the sensation felt... sensation produced is not sudden and transient; but so long as the metals are in contact with the tongue and with each other, so long does the taste continue; and, after some time, it becomes insufferably disagreeable. M. Volta, who adopts the electric theory with various modifications, sensible of the permanence of the effect, in his curious experiments abovementioned supposes, that a stream of electricity passes from the tin cup to the liquor, from this to the tongue of the person making the experiment; then through his body, and returns through the water upon his hands to the cup; and thus he supposes the fluid to move perpetually in a circle. It is surely unnecessary for us to observe, that the supposition of a stream of electricity continually moving in a circle in this manner, is wholly inconsistent with the laws which appear in every case to regulate the motions of that fluid. The same observation applies to the manner in which he explains most of the other phenomena of galvanism.

The electric fluid cannot be put in motion but by destroying the equilibrium to which it perpetually tends; but whenever this is destroyed, all that is required to produce a discharge is, that a single conducting substance be placed between the two points in which it is unequally distributed. Here again there is a very wide distinction between this fluid and the influence discovered by Galvani. M. Volta divides all conductors of galvanism into two classes; 1st, Dry conductors, comprehending metals, pyrites, some other minerals, and charcoal; and, 2d, Moist conductors. He affirms, that it is absolutely necessary, in order to the production of the phenomena, that two conductors of the first class touch each other immediately on one hand, while at their other extremities they touch conductors of the second class. Whether this be admitted or not, we have already stated our opinion that the action of two different substances is absolutely necessary in order to excite contractions; and although it is contended by some writers that a single piece of metal has sometimes been found sufficient, yet even they must allow that, in by far the greater number of cases, it has been found necessary to make use of two metals, and that the effect is even heightened in general by employing three. In the whole science of electricity, we do not know a single fact which bears the slightest analogy to this. Never in a single instance has it been found, that the effects of a Leyden phial have been increased by using a conductor formed of two or more metals in procuring the discharge.

Before leaving the subject of conductors, we may take notice of a very curious and important fact mentioned by Dr. Valli. "Amongst men," says he, "there are some individuals who are good conductors, others who are less so; and some again who appear to be almost non-conductors. I was one day carrying on, with three of my friends, some experiments upon frogs. A frog was put in water, and we each by turn employed its power. Two of us excited strong convulsions, the third only feeble ones, and the fourth none at all. This experiment was repeated frequently with the same result. 'This is not the only example I could adduce of the reality of this fact, but I do not think it necessary to dwell any longer upon it." We have met with one individual who is not sensible of any peculiar sensation when the metals are applied to his tongue. This seems in some measure to corroborate Dr. Valli's observation. It is apprehended, however, that all men are equally good conductors of electricity.

There is still another very marked distinction between the effects of galvanism and electricity. No shock at all resembling that produced by the electric fluid has ever been felt by any person whose body was made a part of the chain conducting the galvanic influence, while a very small quantity of the electric fluid is immediately felt (x). In Dr Robison's experiment with the plates of zinc and silver in the cheeks, there is no doubt a convulsive twitch distinctly felt in the gums; but, as we have already observed, the sensation thus produced is quite different from that which is felt from an electric shock (y).

There is an experiment related by Dr. Valli, which seems to shew that nothing like an electric shock is felt, even when this influence is transmitted through a nerve so as to excite convulsions. Having laid bare the nerves of a fowl's wing, without cutting them, and without killing the fowl, upon applying the metals very smart movements were produced, but the animal remained perfectly tranquil. Nor was this owing to the

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(x) There is an exception to this rule which ought to be taken notice of. M. Cotugno informs us, that when he was one day employed in dissecting a live mouse, he received a sensible shock from the animal. But as neither he nor any other person has ever been similarly affected in any other instance, it seems pretty certain that he was deceived into the belief of a shock from the sensation produced by the struggles of the animal he dissected.

(y) "No one (says M. Humboldt) can speak more decidedly on this subject than myself, having made several experiments on my own person, the seat of which, in some instances, was the socket of a tooth which I had caused to be extracted; in others, certain wounds which I made in my hand; and in others, the excoriations produced by four blistering plasters." The following is the result of these painful experiments. The galvanic irritation is always painful, and the more so in proportion as the irritated part is more injured and the time of irritation more prolonged. The first strokes are felt but slightly; the five or six following are much more sensible, and even scarcely to be endured, until the irritated nerve becomes insensible from continued stimulus. The sensation does not at all resemble that which is caused by the electric commotion and the electric bath; it is a peculiar kind of pain, which is neither sharp, pungent, penetrating, nor by intermissions, like that which is caused by the electric fluid. We may distinguish a violent stroke, a regular pressure, accompanied by an unintermitting glow, which is incomparably more active when the wound is covered with a plate of silver and irritated by a rod of zinc, than when the plate of zinc is placed on the wound, and the silver pincers are used to establish the communication. fowl being in a state of insensibility; for when the nerves were pricked or irritated it screamed violently. But all animals shew signs of great uneasiness from an electric shock.

In general, it must be confessed, that animals under experiments of this kind seem restless and uneasy. The great distinction of which we speak at present, consists in this, that the electric fluid produces a shock and uneasy sensation when any part of the body is introduced into the conducting chain; while the influence discovered by Galvani, on the contrary, when merely transmitted through the body in this manner, gives no shock, nor any sensation whatever, insomuch that we are not sensible of its passage. If this influence be made to act directly on a nerve, there is, no doubt, some kind of irritation produced, as appears from the effect of the metals upon the tongue, the eye, and other nervous parts: but still this action bears no analogy to that of the electric fluid. As the application of the metals to the organs of sense, produces in each organ the peculiar sensation for which it is constructed, as taste in the tongue, light in the eye, &c. so when nerves intended merely for muscular motion are subjected to the action of galvanism, the effect produced is motion in the muscles on which they are distributed.

If this view of the matter be just, it will explain why no shock is felt when the human body is made a part of the conducting chain. In that case the influence does not, in all probability, act directly upon any nerve; and we see that this influence possesses no power, like the electric fluid, of producing a convulsive shock, when merely passed through any part of the body; but it has this peculiar property, when passed directly through a nerve, it excites that nerve to perform the function for which it was intended by nature. To this it will no doubt be objected, that contractions may be excited in different parts of a frog without any division being made in its skin; and here it may be supposed that the influence is not made to pass directly through a nerve. But it ought to be recollected that the skin of these animals is abundantly supplied with nerves, whose trunks communicate at different places with those which supply the muscles; and that the contractions are always strong and easily excited, in proportion as they are applied near to the course of any of the nerves which go to the muscles. But though we had no doubt that the influence might be transmitted through the bodies of these animals, as well as through the human body, without any contractions being produced, we have thought it worth while to ascertain the fact by the following experiment.

A frog was prepared in the usual manner by coating its sciatic nerve with tinfoil, and laying the leg upon a plate of zinc. Another frog, in a very vigorous state, had its fore legs and chisel attached to a rod of silver, and its posterior extremities to a rod of zinc. The silver rod was applied to the tinfoil and nerve of the prepared frog, and the zinc rod to the plate of zinc upon which the leg was laid. Immediately very strong contractions took place in the leg; but no motion, nor the slightest mark of uneasiness, appeared in the other frog through the body of which the influence must have passed. It is necessary in this experiment to dry the body of the frog which is to serve as a conductor very carefully, otherwise the influence might be transmitted by the water upon its surface without passing through its body.

There is an experiment mentioned by Dr Fowler, which shews a striking difference between electricity and galvanism. It was instituted with a view to ascertain the effects of the latter upon the blood-vessels. The Doctor relates it as follows: "Having laid bare, and separated from surrounding parts and from each other, the crural artery and nerve in the thigh of a full grown frog, I cut out the whole of the nerve beneath the pelvis and the knee: I then infusated beneath the artery a thin plate of sealing wax, spread upon paper, and broad enough to keep a large portion of the artery completely apart from the rest of the thigh. The blood still continued to flow through the whole course of the artery in an undiminished stream. The artery, thus partially infusulated, was touched with silver and zinc, which were then brought into contact with each other; but no contraction whatever was produced in any muscle of the limb. This experiment was frequently repeated upon several different frogs, both in whom the nerve was, and in whom it was not divided. The result was uniformly the same. But vivid contractions were produced in the whole limb when an electric spark, or even a full stream of the aura was passed into the artery."

Before taking leave of this branch of our subject, it may be proper to take notice of one fact, which may be thought to militate against the doctrine we have endeavoured to establish. It is said that a frog, exhausted and brought near to a charged electrophorus, has been found to resume its susceptibility. We think this fact may be accounted for without admitting any connection between galvanism and electricity, merely by supposing that the irritability of the muscles, which had been exhausted, was restored by the application of a moderate stimulus, (the electric fluid), of a kind different from those by which it had been exhausted. Such of our readers as are acquainted with the writings of modern physiologists on the subject of muscular irritability, will know that facts of this kind are very common. Thus it has been found by M. Humboldt, that the oxygenated muriatic acid has often restored irritability. To this explanation it will no doubt be objected, that the application of other stimuli, as alcohol and a solution of potash, instead of restoring, totally destroy the susceptibility of galvanism. Suspecting, that although these substances in a concentrated state destroy the susceptibility, yet that when sufficiently diluted, they might be found to have the opposite effect, we tried the following experiment, which confirmed our conjecture.

A frog, 57 hours after it had been decapitated, had ceased for above an hour to be capable of excitement by the application of the metals in any way that could be devised. A few drops of alcohol being diluted with about a tea-spoonful of water, the nerve and the muscles which had been laid bare, as well as the whole skin of the animal, were wet with it. Upon the application of an excitatory arc, composed of four pieces, gold, zinc, silver, and tinfoil, a few very slight contractions of the toes were distinctly observed. After this, no means that we could think of produced the smallest excitement. Alcohol was now applied in a more concentrated state, but without any effect. The same four four pieces of metal which produced the contractions of the toes, had been used before the diluted alcohol was applied, but without effect. We have not tried the application of potash much diluted.

From what has been said, we think we are fully warranted in saying, that although some of the phenomena discovered by Galvani bear a striking resemblance to some of those produced by the electric fluid; yet there are others, and these not the least important, which differ so widely from any effects which have ever been seen to arise from that fluid, that they must derive their origin from some other cause. Our readers may probably think that we have dedicated too much time to this question; but as we conceive it to be the most important point which can be discussed on this subject, we thought it worth while to consider it at some length; and we were the more convinced of the necessity of doing so, from this consideration, that there are still some writers of high authority who maintain the hypothesis, that galvanism and electricity are the same.

The next question that occurs to us with regard to the nature of galvanism is, whether or not it depends upon any law of animal life? To us it appears rather more probable, that the influence which incites the muscles of animals to contract in the experiments of Galvani, is something quite foreign to the animals themselves; as much so as the electric fluid of the Leyden phial is to the animal which receives a shock from it, in both cases the body of the animal acting as a mere conductor. Upon this question, however, we confess that we have neither facts nor arguments to adduce sufficient to warrant our drawing any certain conclusion. It will doubtless be asked, if this influence be something foreign to the bodies of animals, why do we never find it acting anywhere but in their bodies? why is it not, like the electric fluid, capable of being made evident to the senses by its effects upon inanimate matter? The only answer which we are in a condition to give to this question is, that it may very possibly be capable of producing important effects upon inanimate matter, nay, these effects may be the subject of our daily observation; but for want of our being sufficiently acquainted with galvanism to point out the relation between these effects and their cause, the effects themselves are either not explained at all, or ascribed perhaps to some other power, with which they have no connection. In like manner, the electric fluid has doubtless been producing most important effects from the beginning of time; but, prior to the discovery of that fluid, these were either not explained at all, or considered as originating from some cause which, in fact, had no share in their production.

The great difficulty is to obtain some test by which we may detect the galvanic influence when actually present in inanimate matter. Hitherto we have no such test; nor should we know that such an influence exists, but for the effects which it produces upon the bodies of animals through the medium of their nerves. If we had any means of ascertaining its existence, either in a separate state, or conjoined with inanimate matter, the science would make a rapid progress, as it would be easy to diversify experiments so as to discover its nature and effects. To detect it in a separate state is, in all probability, impossible; but that the zeal and ingenuity of philosophers will one day be able to discover some test of its presence in inanimate matter, there seems no reason to doubt.

We have made many experiments with a view to discover such a test, but hitherto without the slightest success. In the trials we have already made, our views have been chiefly confined to the discovery of some chemical effects of this influence upon inanimate matter. M. Volta and other writers, having considered the sensation produced by it upon the tongue as similar to that occasioned by acids, we were not without hopes that it would be found to resemble that class of substances in some of its other properties. We have therefore transmitted it through liquids tinged with the most delicate vegetable colours; but no change in these colours has been effected by the transmission of many galvanic shocks. We have also tried, in the same way, alkaline liquids, without any effect. We next dissolved in water different neutral salts, and other compound bodies, of which the parts are held together by the weakest affinities; but no change has been observed to be produced in them by the transmission of this influence. Our want of success, however, shall not deter us from continuing our efforts; we shall vary the nature of our experiments in every way that shall occur to us as likely to be attended with advantage; and if we should ultimately fail, we trust that others will be more fortunate. Every new fact which is discovered upon the subject tends to facilitate this investigation, by furnishing us with new guides to direct the course of our experiments.

Dr. Fowler is of opinion, that this influence, whatever it may be, is not derived from the metals alone, but that the animals at least contribute to its production, as well as indicate its presence; and he seems to have been led to adopt this theory chiefly from two considerations, neither of which appears to us to have much weight. They are the following: The necessity of a communication between the metals and the muscles, as well as between the metals and the nerves; and the observation, that animals have a more complete control over its effects than one would expect them to have over an influence wholly external to them. But the communication between the metals and the muscles may be necessary to the contraction of the latter, though not to the production of galvanism; which, however, for want of any obvious effect, is not observed. That animals have some control over the effects of galvanism upon themselves, may be very true; but this circumstance does not appear to us capable of proving anything, as they have a control over the effects of other stimuli in the same way. Thus, an animal of any resolution can bear, without betraying any uneasy sensation, a blow which, inflicted unexpectedly, would have produced a convulsive start. The will does not in any degree control the effects produced by galvanism upon our senses of taste, feeling, &c.; that is, the sensations are produced, though we may have resolution not to betray them. But, says Dr. Fowler, the will is not able to control the effects of electricity, when the electricity is otherwise sufficiently strong to excite muscles to contraction. This argument may tend to show, that galvanism differs from electricity; but as it must be admitted, that we can resist the contractions naturally produced by the application of other foreign stimuli, it by no means proves that animals have any power of preventing preventing the excitement or transmission of galvanism. Besides, though we cannot prevent an involuntary contraction of our muscles from taking place when an electric shock of considerable strength is passed through them, yet any man may with his hand draw sparks from the prime conductor of an electric machine without shrinking, though even these sparks would, if he were off his guard, produce a convulsive start.

If the galvanic influence existed ready formed in the muscles or nerves of animals, the only thing requisite to the production of the contractions would be to make a communication between the nerves and muscles, by means of any single substance capable of conducting this influence; as water, for example; but the reverse is known to be true. It may be said, however, that, although there is no proof that any influence naturally resides in the nerves or muscles capable of producing the effects mentioned by M. Galvani, these substances may still, by some power independent of the properties they possess in common with dead matter, contribute to the excitement of the influence, which is so well known to exist in them after a certain application of metals. Upon this part of the subject, the observations of Dr Wells will be found to merit considerable attention.

"It is known (says that gentleman), that if a muscle and its nerve be covered with two pieces of the same metal, no motion will take place upon connecting those pieces by means of one or more different metals. After making this experiment one day, I accidentally applied the metal I had used as the connector, and which I still held in one hand, to the coating of the muscle only, while with the other hand I touched the similar coating of the nerve, and was surprised to find that the muscle was immediately thrown into contraction. Having produced motions in this way sufficiently often to place the fact beyond doubt, I next began to consider its relations to other facts formerly known. I very soon perceived, that the immediate exciting cause of these motions could not be derived from the action of the metals upon the muscle and nerve to which they were applied; otherwise it must have been admitted, that my body and a metal formed together a better conductor of the exciting influence than a metal alone; the contrary of which I had known, from many experiments, to be the case. The only source, therefore, to which it could possibly be referred, was the action of the metals upon my own body. It then occurred to me, that a proper opportunity now offered itself of determining whether animals contribute to the production of this influence by means of any other property than their moisture. With this view, I employed various moist substances, in which there could be no suspicion of life to constitute, with one or more metals, different from that of the coatings of the muscle and nerve, a connecting medium between these coatings, and found that they produced the same effect as my body. A single drop of water was even sufficient for this purpose; though, in general, the greater the quantity of the moisture which was used, the more readily and powerfully were contractions of the muscle excited. But if the mutual operation of metals and moisture be fully adequate to the excitement of an influence capable of occasioning muscles to contract, it follows, as an immediate consequence, that animals act by their moisture alone in giving origin to the same influence in M. Galvani's experiments, unless we are to admit more causes of an effect than what are sufficient for its production." We do not quote the above reasoning as perfectly conclusive, for it by no means appears to us to be so; but it certainly gives some probability to the opinion, that galvanism is, as M. Volta supposes, the result of the action of two dry conductors, which touch each other immediately on one hand, while at their other extremities they touch conductors of what he calls the second class. (that is, moisture, for all the conductors of the second class contain water), and that the bodies of animals act merely as moisture.

One of M. Humboldt's experiments related above, appears to us to strengthen the conclusion, that the influence discovered by Galvani is something perfectly foreign to the bodies of animals. Can it be supposed that any substance which naturally resides in our bodies, should, in a few seconds after it is put in motion, convert the simple ferous discharge of a blister into a dark coloured fluid, of a nature so acid as to irritate and violently inflame the skin wherever it touches it? We do not say that this is impossible, for we are too little acquainted with the laws of secretion to say with certainty what may, or what may not, produce such a change; but we know no similar alteration produced, in a few seconds, by a mere change of action in the vessels themselves.

We shall not undertake to determine the nature of the cause which produces such astonishing effects. We think it is certainly not the electric fluid, and probably something which resides or is formed in the excitatory arc, but we consider our knowledge of galvanism as still in its infancy, and our stock of facts as infinitely too small to admit of our forming a just theory on the subject. Fortunately, however, the discovery of Galvani has attracted to much the attention of philosophers in every part of Europe, that new facts may be expected to come to light every day; and we hope the time is not very distant, when these may be so classified, as to entitle the subject to be ranked among the sciences.

While this article was in the press, we were favoured by a friend with an account of some German dissertations on the subject, which we are obliged to insert in this irregular manner.

Mr Creve, surgeon in Wurtzburg, had an opportunity of observing the galvanic irritation on the leg of a boy, which had been amputated far above the knee in the hospital of that city. Immediately after the amputation, Mr Creve laid bare the crural nerve (kniekehlnerven), and surrounded it with a flip of tinfoil. He touched at once the tinfoil and the nerve with a French crownpiece. In that instant the most violent convulsions took place in the leg both above and below the knee. The remainder of the thigh bone bent with force toward the calf; the foot was more bent than extended. All these motions were made with much force and rapidity. None were produced when the tinfoil was taken away, or when a steel pincer was used in place of a piece of silver, or when the tin or silver was covered with blood; but they were renewed... ed when these obstacles were removed. These phenomena continued till 38 minutes after the amputation, when the limb became cold.

Dr. Christopher Heinrich Pfaff (in Dissertatione de Electricitate Animali, Stuttgart, 1793; see also Gruen's Journal der Physik, T. viii. p. 196, &c.) has classified the phenomena in a very orderly and perspicuous manner; and the result of the numerous experiments made by himself and others corresponds very nearly with our inferences in the preceding pages.

I. Phenomena of muscular contraction.

The general form of his experiments is the same with that which we have placed at the beginning of this article; but the following varieties were observed:

The nerve being coated with tinfoil, it was always observed that the contractions were stronger when the silver first touched the muscle, and then the coating. If it touched the coating first, the effects were always, and very sensibly, weaker.

They were still stronger when the silver did not touch the muscle at all, but only the nerve and its coating.

When the contractions were weaker at the beginning, they also ceased sooner.

No contraction ensued from touching the coating only, or the nerve only, or the muscle only, with the silver.

Continuing the contact did not occasion any repetition of the contractions, except in some cases, where the silver was drawn along different parts of the coating, while its other end remained in contact with the nerve.

The contractions took place only in the muscles to which the nerve led.

Their strength and duration were greater when the surfaces of contact were greater, and when the two metals touched each other in points or sharp edges.

A ligature, with a silk thread below the coating (that is, between the coating and the muscle, or part of the nerve touched by the silver), prevented all contraction; but not if the ligature was between the coating and the brain. If the nerve was cut through below the coating, and the parts separated a quarter of an inch, no contraction followed by touching the coating and the nerve or muscle; but it took place, if the parts were brought into contact; or even if a piece of any other nerve was put between the parts.

If a considerable part of a bared nerve was insulated and coated, partly with tinfoil and partly with silver, contractions were produced in the muscle to which it led whenever the two metals were brought into contact.

If one crural nerve be coated with tin, and the other with silver, contractions are produced in both legs by bringing the metals into contact.

If the nerve be dry under the coating, or when the silver touches it, or in both places, we have no contractions; but they begin as soon as we moisten the nerve.

Dr. Pfaff infers from these phenomena, that the nerve alone is subject to the irritation produced by the two metals.

If the prepared frog be immersed in water, so that the coating touches the water, contractions are produced by touching the coating above water with the silver, while another part of the silver touches the nerves, or the muscle, or even dips pretty deep in the water.

No such thing happens in oil; or, at best, the contractions are very slight.

Dr. Pfaff could not produce contractions without employing two metals, or a metal and charcoal.

A very thin covering of muscular flesh on the nerve did not altogether prevent the contractions, and in many cases did not sensibly diminish them.

If a piece of silver be laid on the muscles of the breast or belly, and be brought into contact with the tin-coating on the lumbar region, only the muscles of the breast or belly are affected, but not those of the legs.

Dr. Pfaff says, that the involuntary muscles are not affected by galvanism; and refers for convincing proofs to a dissertation by Dr. Ludwig, shewing that the heart is not furnished with nerves, (Scriptor. neurolog. minor. selecta, vol. 2.).

II. Irritation of the Organs of Sense.

Here Dr. Pfaff's dissertation contains nothing remarkable.

III. Conjectures as to the Cause.

Dr. Pfaff uses the same arguments that we have employed to refute the opinion of a similarity between the animal organs and the Leyden phial, and the opinion that electricity is the agent. He mentions the opinion of those who maintain that the agent is a fluid put into motion by means of its relation to the metals only, in their action on each other, and who consider the animal as merely serving as a conductor; and also serving, by its irritability, to give us the information of the presence of such a fluid, in the same manner as another kind of irritation, somewhat analogous to it, indicates the presence and agency of the electric fluid. It may therefore be called the Metallic Irritation; a term which will sufficiently distinguish it.

But Dr. Pfaff seems rather to think that the agent resides in the animal, and that the metals are the conductors (See a dissertation, entitled, Further Contributions to the Knowledge of Animal Electricity, in Gruen's Journal der Physik, T. viii. p. 377). This fluid he conceives to be intimately blended with the principle of life; nay, perhaps, to be the same. He mentions a thought of Professor Kielmayer, "that it may resemble the magnetic fluid in its manner of acting, giving connection to the dilute particles of a nerve, as we observe a magnet give an instantaneous connection to each of a parcel of iron filings; all of which it would arrange in a certain precise manner, if they were sufficiently moveable, by giving momentary polarity to each." This somewhat resembles Newton's hypothetical whim read to the Royal Society, describing what may be done by means of an ether (See Birch's History of the Royal Society).

But all this is vague conjecture, and merits little attention. This will be better bestowed on an observation of M. Humboldt of Jena, "that a bit of fresh morelle (the Helicella mitra of Linnaeus) may be substituted for a bit of nerve in the animal arc in these experiments." This is the only vegetable substance yet discovered to have this property. If the nerve be laid on the morelle, we have only to touch the morelle with the zinc, and the muscular contractions immediately follow.

GARDECAUT.