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II. The EXCITATORY ARC is ufually formed of three different pieces, made of different metals. Of thefe, one must be in contact with the nerve; the other muft touch the muscle; and the third muft form the mean of communication between these two. This arrangement, though not indifpenfibly neceffary, is at least the moft convenient.

In refpect to the EXCITATORY ARC, the committee examined, ift. The application of metallic fubftances to form it: in refpect to which they endeavoured to afcertain the number and the diverfity of the pieces of metal, of which this arc may be compofed; the metallic mixtures or alloys which are capable of being employed for this ufe; the particular degree of the friction of one metal upon another, which is favourable to the exhibition of the phænomena; the different ftates, in respect to Galvanism, of metals differently mineralized. 2dly, The ef


fects of the use of carbonic fubftances in forming the excitatory arc. 3dly, The effects in the fame formation, of bodies, which are either non-conductors, or elfe very imperfect conductors of electricity, fuch as jet, afphaltus, fulphur, amber, fealing-wax, diamond, &c. 4thly, The confequences of the interpofition of water, and of substances moiftened with water, between the different parts of the excitatory arc. In forming their excitatory arcs too they made themfelves the chord of the arc, they introduced into it animal fubftances which had loft their vitality; they rubbed the fupporters with the dry fingers, fo as to mark them with nothing but the traces of the perspiration from the fkin. They made, likewife, fome experiments for the purpose of afcertaining the relations between, on the one hand, the extent and magnitude of the furfaces of the parts compofing the arc, and on the other, the effects produced by its energy. From their experiments they have alfo drawn foine inferences concerning the relative efficiencies of the feveral conftituent parts of the exciting arc. It is impoffible for us here to relate in detail all this train of experiments. The following corollaries exprefs the fubitance of thofe general truths, which their authors were led to infer from them.

1. The excitatory arc poffeffes the greateft power of Galvanifm, when it is compofed of at least three diftinct pieces; each of a peculiar nature; the metals, water, and humid fubftances, carbonaceous matters, and animal fubftances, Atripped of the epidermis, being the only materials out of which thele pieces may be formed.

2. Nevertheless the excitatory arc appears to be not deftitute of exciting energy, even when it confiits but of one piece or of feveral pieces, all of one proper subftance. In general it must be owned, identity of nature in the constituent pieces, and particularly in the fupports forming the extremities of the arc, diminifhes, in a very fenfible manner, its Galvanic energy.

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

4. As the animal arc is fufceptible of being in part made up of metallic subftances, or fuch others as are adapted to enter into the compofition of the excitatory arc; fo, on the other hand, the excitatory arc admits of being in part formed of thofe fubftances 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 feparation of their component parts, or a leaft by the feparation of these parts to a certain diftance.

6. Even the finalleft degree of moisture is fufficient to join the parts of the excitatory arc, and to determine their effects upon the animal arc.

7. The influence of the ftate of the atmosphere, and of furrounding circumftances, upon the fuccefs of the experi ments of Galvanilin, is, confequently, very great. In order therefore to perform thefe experiments with due accuracy, the state of the hygrometer, and of other meteorological initruments, must be vigilantly inspected, during their progrefs; and the influence of the perfons making the experiment upon the phere within which it is made, muft, likewife, be carefully attended to.

8. The experiments which were made to afcertain the nature of the animal arc, together with thofe made upon the excitatory arc, with a view to the comparifon of the effects of the fleth 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 fuggeft to us, that the epidermis is one of thofe fubftances which diminish or interrupt the efficacy of the excitatory arc. The epidermis is, as well as the hairs and brittles of animal bodies, among the number of thofe fubftances which deferve the appellation of idio-electrics.

9. Examine the fubftances which are fit for the formation of the excitatory arc, and you will find that the greater part of thofe which have been fuccefsfully put to this ufe are fubftances capable of acting as conductors of the 'electrical fluid; but that the fubftances which interrupt the operation of Galvanifm are generally fuch as are well known alfe to refift the tranfmiffion 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 tranfmitting furfaces.

III. The committee appear to have ufed no lefs care and difcernment in experiments upon thofe circumftances, which though different from the ftructure of the Galvanic circle and its two conftituent arcs, have, however, a decifive influence upon the exhibition of the phenomena of Galvanifm. Some curious obfervations were made on the differences in the state of the parts expofed to the Galvanic action. It was afcertained, that, frogs fresh from the ditches, did by no means exhibit the fame phænomena as thofe which had been during fome days preferved in the houfe; nor did the limbs of animals, when recently ftripped of the fkin, prefent the fame appearances as after they had been fubjected to a variety of Galvanic experiments; nor were the fame effects to be produced upon the parts of animal bodies, which, after a certain number of trials, had been left for a while at reft, and then taken up again, as upon thofe which had been fubjected to one continued train of experiments. The committee next examined the variations in the fuccefs 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 fupporter to the other: when the communicator is brought into contact with the fupporter, or is withdrawn from actual contact with it; when the communicator is brought flowly, or when it is brought rapidly, into contact with the Supporter; the effects are nearly the fame:

and a fmart convulfion is, in all these cafes, produced at the moment of the commencement of the mutual contact, or of its ceffation. But, when the frog is fatigued, the effects are different. Thefe fucceffive experiments likewise affect the refults of one another, by means even of their fucceffion folely. And they are alfo naturally fubject to be influenced by the nature of the media, amidft which they are performed; fuch as common air, water, an electrical atmosphere. The following are the inferences which have been deduced from this clafs of these experiments.

1. In many cafes the Galvanic energy is excited by exercife, is exhausted by continued motion, is renovated by reft.

2. The multiplicity of the caufes by which the experiments of Galvanism are liable to be influenced to fuccefs or failure, is fo great, that we cannot, as yet, be too cautious in either rejecting or believing thefe accounts which we hear, of the fuccefs of any fuch experiments; unlefs 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 refpects the continuation of the Galvanic fpatin.

The communicator being fupported by the hand, and refting, feemingly, without change of pofition, ftill upon the fame 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 fmalleft poffible change in the relative fituations of the parts of the Galvanic circle and the excitatory arc, is capable of producing an effect upon the fuceptible animal, and of occafioning mistakes in regard to the fuccefs of the experiment, if the utmost care be not taken to notice and eftimate every variation that can happen.

4. The truth of the foregoing propofition is farther confirmed, by the experi ments upon the manner in which the Galvanic movements are affected by the advancing or the withdrawing of the com municator. For thefe experiments fully evince the neceffity for the most vigilant obfervation of every moment in the procefs of an experiment, not only collectively, but in their fucceffion, and at the different periods of the operation.

5. It should feem that there are, in the formation of the excitatory arc, independ ently of its modes of acting in the Gal

vanic operations, certain enervating, and certain exciting difpofitions; of which, fome not only augment or diminish the energy in the prefent inftance, but, befides, difpofe the animal to a greater or a fmaller fufceptibility, under-fubfequent experiments.

6. In order to accuracy of experiment, and to the correct afcertaining of the effects of an experiment, it is of great importance to know the precife ftate of the animal, the manner in which it has been preserved and fuftained to the prefent 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 wifhed, that in making a statement of experiments of different forts these fhould be arranged in the order of their efficacy, and that there might thus be formed a Galvanic fcale, which fhould help us to determine the precife degree of the Galvanic fufceptibility of any animal in this or that particular ftate or pofition, fhould direct us in fubjecting every fuch animal only to experiments fuitable to its particular fufceptibility; fhould enable us to estimate, from the efficacy or inefficacy of our experiments, the Galvanic value of the circumstances in which we every day find ourfelves, and should enable us to judge when the fuccefs or miscarriage of an experiment can afford room for certain conclufions abfolutely 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, 1ft, the influence of electricity upon that fufceptibility; 2. the effects of the mufcular organs, and of certain liquors, fuch as alcohol, the oxygenated muriatic acid, the solutions of potash and opium, upon the Galvanic properties; 3. and at the medical fchool of Paris they made a number of experiments, in order to afcertain what new modifications the Galvanic energy undergoes in various cafes of fuffocation or asphyxia. These last-mentioned experiments were made upon hot-blooded animals, of which fome were reduced into the state of afphyxia by fubmerfion, fome by ftrangulation, fome by the action of gafes, while others were killed in vacuo by the difcharge of the electric fpark. In that fuffocation which was produced by fulphurated hydrogenous gas, by carbonic vapours, and by fubmerfion in which the animal was fufpended by the hinder feet, MONTHLY MAG, No. XLIII.

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the Galvanic fufceptibility was entirely deftroyed. The Galvanic fufceptibility was only fufpended by fuffocation produced by the pure carbonic acid confined under mercury. It was diminished, but not deftroyed, in thofe cafes of fuffocation, which were occafioned by fulphurated hydrogenous gas that had loft a portion of its fulphur, by gas. ammoniac, gas azote, or fuch gafes as had been exhaufted of their pure air by refpiration; and the fame thing was found to take place in animals which had perished by total fubmer fion. But the Galvanic fufceptibility furvived unaltered in fuffocations brought on by fubmerfion in mercury, by pure hydrogenous gas, by carbonated hydrogenous gas, by oxygenated muriatic acid, by fulphureous acid; as alfo when the fuffocation was occafioned by ftrangula tion, by the abftraction of the air in the air-pump, or by the difcharges from an electrical battery. The refults of the experiments at the medical school suggested the following reflections:

1. Though it be true that all cafes of fuffocation refemble one another in the privation of refpirable air, and in the fufpenfions of the functions of refpiration, and of the circulation of the blood; yet, in their other circumstances, they are fubject to great differences, arifing from diverfity of nature in the fubftances by which they are occafioned.

2. Of these caufes, fome appear to act with a more thorough efficacy, penetrating at once all parts of the nervous and mufcular fyftems. Others again feem to act but fuperficially, producing only pulmonary afphyxia, with its immediate effects.

3. One of the moft remarkable changes not confined to the organs of refpiration, confifts in the alterations produced on the Galvanic fufceptibility. In that refpect

the various cafes of afphyxia differ greatly one from another.

4. The ftate of the irritability of the mufcles, when examined by means of bodies, the mechanical action of which caufes the mufcles to contract by irritating them, is far from always correfponding to the state of their Galvanic fufceptibility.

5. Laftly, the caufes of fuffocation or afphyxia, do not act upon all parts of the mufcular fyftem in the fame manner. But the heart is very often found in a state extremely different from that of the other. mufcles.

V. The comparison between the phanomena of GALVANISM and thofe of ELECTRI

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ELECTRICITY is perhaps one of the most interefting objects of attention in the whole body of animal phyfiology.. It is well known that GALVANI was accidentally led to his discovery by obferving the motions of fome frogs, at a certain diftance from an electrical machine difcharging fparks. The committee from the inftitute made, therefore, fome attempts to afcertain the relations between electricity and Galvanifm. Having first paid due attention to the fufceptibility of animals toward the influence of electricity, they then fought to difcover to what precife degree animals divested 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 fufceptibility of electricity with the fufceptibility of Galvanifm, they perceived that quantities of the electrical fluid, fuch as are ftill capable of being very accurately measured by the electrometer, are, however, often too weak to act upon a frog that retains the most perfect fenfibility to all the energy of Galvanifm. The members of the committee purpose to profecute farther their experiments upon this part of the fubject..

VI. The following are the general refults of the experiments made by M. HUMBOLDT in the prefence of the committee ::

1. There is no truth in the affertion of certain phyfiologists, that the experiments of Galvanifm fail when tried upon the heart and thofe other muscles of which the contractions depend not upon volition. For thefe organs have been found to be actually fubject to the inluence of Galvanifm.

2. The effects of Galvanifin are liable to be interrupted by the conftriction of a nerve, whenever both the nerve and the conftricting ligature are enveloped in the Alefh of the animal body.

3. The powers of the exciting are may be renovated or destroyed, even though its fupporters remain the fame, 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 Galvanifm. 5. There are fubftances which, though in an eminent. manner conductors of electricity, yet interrupt the motions of Galvanifm.

M. HUMBOLDT had performed alfo other experirents, which, when he attempted to repeat them before the committee, could not be brought to fucceed, on account, as was fuppofed, of the fea-fon of the year.

Such are the principal refults of this very valuable train of experiments upon Galvanifm. It is eafy to difcern, that they have only opened up, for a few paces farther, a path, of which there remains yet very much to be explored, and which promifes difcoveries the most interefting and important to the philofopher and the physician..

"For the Monthly Magazine..

DR. MITCHILL'S SECOND LETTERS (See p. 108 of our last Number.)



OU are candid enough to affure me, and a number of our friends, "that you felt a confiderable fhare of pride for the female fex, after perusing a little note: to Mifs -> of laft November, in Meff.. Swords's Magazine, and, as they fay, afcribed to me." I believe the leading fentiment there advanced is true, that women have always and uniformly obviated and extinguished peftilence by more rational and fuccessful means than the men: have followed. This is owing, as you obferve, to the ufe of alkaline fubftances in a great variety of their domeftic operations.

In addition to what is there brought to notice, you obferve, "that the modern fashion of difcarding all fmelling-bottles, and. other applications to the noftrils, on the advice of certain of our diftinguifhed men muft be adopted with limitation: for however ufelefs it may be to employ thieves'-vinegar, rue, camphor, and other things of thofe kinds, it certainly cannot be improper; it may be advantageous to the. ladies to comfort themselves with a little spirit of fal ammoniac, a phial of hartshorn, and fome volatile falts, in times of general. fickness." Why, certainly, madam, you are right in your remark. You fee in this inftance the old established custom is

good one, and ought not to be difcontinued. It is cruell and injurious in the men to deprive you at all of these wholefome precautions; but to do to under pretence of long obfervation or experience of their inutility is a great deal worse. If it fhould ever be your misfortune to in-habit a place where a fickly air prevails, you may fafely and truly advise your fe male friends to perfift in the use of these agreeable and reviving odours: they are preventives and antidotes, and act by neutralizing the acid vapours of peftilence which enter your noftrils, and affail your. life. Do not mind, therefore, thofe would-be

would-be philofophers, who are fo ready with their advice on all occafions. I af fure you, I had rather fide with you than with them; and when I am with you, Afhall confider myself quite out of harm's


You fay," that if the principle laid down in the letter referred to, is jutt, then it follows, that pot-afb cakes fhould be good for children; for pot-afh, as well as volatile falts, is an alkali. It will prevent the mifcievous effects of an acid upon their stomachs, and calm the diforders to which their little bowels are fubject." There again you are right: that fort of bread is, indeed, good for them. Do you not fee, where the experiment is fairly made, how fat and hearty they grow by eating cakes tinctured a little with that excellent material. If it

would not divulge too much of a fecret in the practice of phyfic, I would tell you, that this very thing pot-afb, which women have fo great a duration of time mingled with their cakes, is a grand remedy in various diforders of the alimentary canal to which infants are subjected. But I hope you will not give them all to your children; on the other hand, bring them on the table in the evening; for I declare, that, next to your engaging manners and converfation, few things can give a more agreeable relish to the tea, when I have the honour to fip it with you, than good pot-afb cake.

It is enquired by you further-Oh, dear! how minute you are!" Whether, as acids corrode and deftroy the teeth of certain ladies of our acquaintance, alkaline wabes and powders would not be good for thein?" To be fure they would; and you may now understand, that if foot or fine afbes have ever been beneficial as dentifrices, it is by virtue of the alkaline matter with which they abound. The former contains ammoniac, and the latter pot-afb; and these are the active ingredients in both. A weak folution of pearl-afh in water is better than either, being more efficacious, as well as more neat and convenient. The mouths of many perfons are manufactories of fuch acids as eat away the teeth, and give a peftilential taint to their breath. How unclean and odious is this feptic venom and yet it is wholly deftructible by alkalies. It at once afflicts and difgufts me to witnefs the confequences of that neglect with which thefe handy and fimple applications are treated. Then you beg me to inform youI cannot proceed any further at prefent; for you ought to recollect, that, as much As I delight in obeying your commands,

I must attend a little to the business of the legiflature. We have in hand the nuifance-bill for the city of New-York; and I wish it was in our power to alkalize every foul thing there. You muft, therefore, give me credit for my condefcenfion in thus vouchfafing, while I have the great affairs of the ftate to engage me, to anfwer your questions about mellingbottles, ginger-bread, and tooth-afbes.

The weather is dreadfully cold, and my fingers are almost benumbed; though they are still flexible enough to guide the pen while I affure you that, &c. &c. SAM. L. MITCHILL.

Albany, Feb. 3, 1798.

To the Editor of the Monthly Magazine.


HE account of Profeffor, Eickhorn's

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T Introduction to the Old Teftament," given in the Appendix to the 23d volume of the Monthly Review enlarged (from May to Auguft, 1797) is fo interefting, that many perfons unacquainted with the German language must be defirous, I imagine, of feeing a tranflation of that very important work.

I take the liberty of afking, through the channel of the Monthly Magazine, Whether a tranflation of the whole, or of any detached parts, is now in hand?

It feems to be, by fuch fort of criticifm as this work contains, that the petulant objections of unbelievers on the one hand, and the orthodoxy, as it is called, of churchmen on the other, is to be corrected, and we are at length to make fome nearer approaches to truth.

If the following paffage, inferted in the Review, fhould be enlarged upon and elucidated in the work, a tranflation would probably be a valuable acquifition, as a detached part.

"Certainly thinking men would have reconciled themselves to thefe important monu

ments of human intellect, if but one expounder of their contents, if but one defender of their importance, had arifen, to fhew that the greater part of this miraculous and of this fupernatural, is not to be found in the books themfelves, but has refulted from mifunderstanding;-from ignorance of language; from inattention to the mode of thought and expreffion, which characterizes these in common with the other earliest productions of literature ;--from mifapprehenfion of the fpirit of the Eaft ;-or from impotence of fympathy with the childhood of intellect, fo as to view all things through a fimilar medium of imagination." Your's, &c.

M. C. For

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