Part 2
To ensure the success of this interesting experiment, the nerves must be prepared as speedily as possible, by disengaging them from every foreign substance. It will be proper also to apply the nerves not to one but to several points of the muscle, throughout its whole length. It is observed, that the contact of the nerves with the tendinous parts which communicate with the muscles, often serves to increase the muscular contractions. I performed the above experiment before several able professors, among whom were the celebrated Brugnatelli and Carcano, who, with that modesty peculiar to them, made several ingenious observations on the precision which might be given to it. Professor Brugnatelli was apprehensive that, as I had accidentally touched some metals before I performed the experiment, metallic particles might have adhered to my fingers, and thus have served, in some measure, as invisible arming, sufficient of itself to excite muscular contractions. This suspicion, however, I removed, by immersing my hands in water, to detach every foreign substance. He then observed that animal moisture, independently of the circulation of the Galvanic fluid from the nerves to the muscles, might also excite muscular contractions; and he requested that the crural nerves might be washed in common water. This was accordingly done; and the humidity of the nerves being thus externally removed, very strong contractions were still produced, as the professor found, to his full conviction, on repeating the experiment himself several times[1].
[1] It may not be improper here to observe, that my method of exciting muscular contractions, without metals, is very different from that proposed by others. I do not know that convulsions have ever been obtained in cold-blooded animals by means of warm-blooded. From observations I have made, I flatter myself with the hope of being able to obtain contractions without metals, even in the muscles of warm-blooded-animals. But to ensure the certainty of this method would require long practice, and a preparation attended with considerable difficulty. I however propose to attempt it on my return to Italy. Some philosophers, indeed, had conceived the idea of producing contractions in a frog without metals; and ingenious methods proposed by my uncle Galvani induced me to pay attention to the subject, in order that I might attain to greater simplicity. He made me sensible of the importance of the experiment, and therefore I was long ago inspired with a desire of discovering that interesting process. It will be seen in the _Opuscoli of Milan_, that I shewed publicly, to the Institute of Bologna, contractions in a frog without the aid of metals, so far back as the year 1794. The experiment, as described in a memoir addressed to M. Amorotti, is as follows: “I immersed a prepared frog in a strong solution of muriate of soda. I then took it from the solution, and, holding one extremity of it in my hand, I suffered the other to hang freely down. While in this situation, I raised up the nerves with a small glass rod, in such a manner that they did not touch the muscles. I then suddenly removed the glass rod, and every time that the spinal marrow and nerves touched the muscular parts, contractions were excited. Any idea of a stimulus arising either from the action of the salt, or from the impulse produced by the fall of the nerves, may be easily removed. Nothing will be necessary but to apply the same nerves to the muscles of another prepared frog, not in a Galvanic circle; for, in this case, neither the salt, nor the impulse even if more violent, will produce muscular motion.
EXPERIMENT III.
The Commissioners of the French National Institute remarked, that, in order to give the greatest precision possible to these experiments, it would be necessary to insulate entirely the nervous and muscular systems. For this purpose, I applied these parts to each other by means of glass rods, and each time they were brought into contact I obtained muscular contractions. The case was the same when an animal arc was applied to two insulated frogs: contractions were produced in them both. The apparatus employed for this purpose may be seen in Plate I. fig. 5 and 6.
EXPERIMENT IV.
Having prepared a frog according to the usual method, I cut one of its crural nerves in such a manner that the trunk was united to the spinal marrow by means of the other nerve, which remained uncut, and also by a blood-vessel contiguous and parallel to the cut nerve. I then repeated the above experiment; and, though only one nerve was in contact with the muscles, I obtained the same results.
EXPERIMENT V.
A ligature was placed loosely around the middle of the crural nerves, and one of these nerves at the ligature applied to the corresponding muscles: strong contractions ensued; which, however, did not take place, when the ligature was drawn tight, at the insertion of the nerves into the muscles of the thigh.
PROPOSITION VII.
_The heterogeneity of metals contributes, in a great degree, to excite muscular contractions with more facility, but is not absolutely necessary to their production._
This proposition I could demonstrate in a direct manner, by means of experiments, which I published formerly, on the contractions excited by very pure mercury, and which were repeated, in different ways, by the celebrated Humboldt. I am, however, happy to have an opportunity of examining the influence of arming with heterogeneous substances; and I shall endeavour to prove that it cannot, of itself, produce the effect of muscular contractions.
EXPERIMENT I.
If several prepared frogs, ten or more for example, be placed on a table (Plate I. fig. 7.), and arranged parallel to each other, in such a manner that the whole system of the nerves shall be at one end, and that of the muscles at the other,—on applying two armatures and a metallic arc to the first of these frogs, muscular convulsions will be immediately excited, not only in the first frog, but in all the rest.
EXPERIMENT II.
If the experiment be repeated with the frogs arranged in such a manner that the spinal marrow and muscles are not each at one end (Plate I. fig. 8.), but disposed alternately so that the spinal marrow of one touches sometimes the muscles of another, or vice versa, convulsions will then be produced only in some of the frogs, and not in the whole series. This experiment proves that the effect does not, in any manner, depend on the action of metals; because metallic electricity in the first experiment ought to exercise an action only on the first frog, and not on the rest; and, in the second, ought to cause them all to move together, or to leave them motionless.
I shall now proceed to those experiments which appear to be best calculated to support the opinion of the great analogy between electricity and Galvanism.
PROPOSITION VIII.
_The Leyden flask, the Voltaic pile, and animal substances, have the faculty of absorbing principles from the atmospheric air in an insulated plenum._
EXPERIMENT I.
By means of a metallic point, I electrified the interior side of a glass jar, which I inverted and placed on a plate of metal, so as to form an insulated plenum. In a little time, I saw the water rise in the glass several lines; and I then flattered myself with the hopes of obtaining some remarkable effects by another method.
EXPERIMENT II.
I provided for this experiment a Leyden flask, seven inches in height and about three in diameter, coated in the usual manner with tin foil: the exterior end of the wire terminated in a sharp point, so that the electric fluid which escaped from it could easily combine with the principles of the atmospheric air, with which it had a greater affinity. I then electrified the jar, and covered it with a glass receiver of such a size that its electricity could not be weakened by the sides of the latter. I thus formed an insulated plenum, and at the end of half an hour I saw the water ascend in the receiver in a very sensible manner.
EXPERIMENT III.
Having made the wire to terminate, not in a point, but in a metallic knob, as usual, I again charged the jar, and having placed it under a common receiver, at the end of about half an hour I found that the elevation of the water was much greater. To remove every suspicion that this might arise from the water employed in the preceding experiment, to insulate the plenum, I substituted mercury in its stead; and though the elevations were less, they were, however, analogous to those which had been observed a little before with water. By repeating this experiment with a similar jar, not electrified, one may be easily convinced, that the elevation of the water in the bell ought not to be ascribed to a difference in the temperature of the air within it.
EXPERIMENT IV.
I placed under a bell-glass, forming an insulated plenum, a pile consisting of fifty plates of silver and zinc. Next morning I observed that the water had risen some inches, indicating that a great absorption of air had taken place. Having then introduced a taper into the receiver, it was immediately extinguished. The pile, without being arranged anew, was placed under the same receiver; and on forming an insulated plenum, I observed, after twenty-four hours had elapsed, a sensible absorption of air. A taper was then introduced, and I obtained the same result. I replaced the pile under the receiver, and found, on the third and following days, that the pile retained its moisture, so that till the tenth day it gave analogous results. I repeated the same experiment with oxygen gas, and found, six days after, that the water in the bell had risen a foot.
EXPERIMENT V.
The same results may be obtained without employing large piles and large receivers. In general, it will be sufficient to arrange, in alternate strata, some plates of heterogeneous metals. If two plates of copper and zinc be placed under a bell an inch and a half in diameter, and three inches in height, and if an insulated plenum be then formed, two days after the water will have risen about half an inch. Having repeated the experiment with different metals, I found that a greater or less absorption of air had taken place, according to the difference of their nature and combination. This inspired me with the idea of making a series of experiments with different metals; and I hope to be able, at some future period, to form a table of the different heights of the fluid, which may serve to determine how far they are respectively susceptible of oxidation. However, to ascertain the oxidation of metals with precision, pieces of coin mixed with alloy ought not to be employed. Pure metals, formed into small piles, must be subjected to observation, and ought to be placed under equal bells, at the same temperature as that of the atmosphere. Until it be proved that the absorption of oxygen in the above experiments is merely a chemical effect, altogether unconnected with the action of Galvanism, I think I may be allowed to avail myself of it to prove the proposed analogy.
EXPERIMENT VI.
The ingenious theory of Girtanner, who ascribes the cause of muscular contractions to oxygen, the curious experiments by which Professor Humboldt revives the muscular force, by means of oxygenated muriatic acid, and those made by the celebrated Fourcroy on the same subject, induced me to examine the effect resulting from a combination of oxygen with muscular fibres, in a state of the greatest vitality. For this purpose, I adapted to a bell-glass a bent metallic wire, from which were suspended fourteen frogs, prepared with the utmost dispatch, and almost at the same instant, by myself and several of my pupils; and having formed an insulated plenum, I found, at the end of twenty-four hours, that the water had risen in the bell to the height of about half an inch.
EXPERIMENT VII.
I repeated this experiment, with the same success, on warm-blooded animals. I provided, for that purpose, the extremities of different pullets from which the crural nerves had been previously separated, and found that the elevations of the water, in the insulated plenum, were much less when I employed the fibres of these animals after their vitality had been weakened.
EXPERIMENT VIII.
Having obtained the bodies of some executed criminals, I exposed to the action of an insulated plenum the nervous and muscular fibres, and the substance of the brain. The elevations of the water were remarkable, in consequence of the different substances subjected to experiment, which, according to their different characters, exercised a different action on the oxygen. This fact ought to induce physiologists to undertake experiments of a similar kind with other gases, to enable them to determine the strength of the affinity exerted by animal substances to combine with oxygen.
EXPERIMENT IX.
As fishes, and in particular the torpedo, furnish a large quantity of animal or Galvanic electricity, I was inclined to think they would exhibit the before-mentioned effects in a very striking manner in an insulated plenum. I mentioned to Professor Mojon of Genoa the experiment I proposed to make; and, in a letter which I lately received from him, he informed me of the result, as follows:
“I took a strong torpedo, and, as soon as it was dead, armed its nerves with the usual armature. Having then placed it on an insulating stool, a little elevated above water, I covered it with a bell-glass the content of which was equal to 432 cubic inches. At the end of some hours I observed, with great surprise, that the water under the insulated plenum began to rise progressively during about ten hours; and at the end of forty-eight I found that it had risen an inch; so that it occupied a ninth part of the capacity of the bell, that is to say, forty-eight cubic inches. I analysed the remaining air, and found that the bell contained no more than 80 cubic inches of oxygen gas, and 324 of azotic gas; and that, during the above period, more than two-fifths of the oxygen gas contained in the bell had been absorbed.”
I propose going to the sea-coast, in order that I may repeat the experiment on the torpedo without any armature; and I shall embrace that opportunity of making various researches in regard to the new theory of Galvanism. I think it necessary, in general, to submit to new experiments the different animal parts immersed in the different aëriform fluids, fixing their various combinations according to the degrees of Galvanic force which they may possess.
PROPOSITION IX.
_Flame prevents the action of the Leyden flask, as well as that of the pile, and also muscular contractions._
EXPERIMENT I.
I placed a lighted taper on an insulating stool; and having made the wire, proceeding from the interior coating of a charged Leyden flask, to pass through the flame, I found that, without forming an arc, it lost a portion of its electricity. If the experiment be repeated in such a manner that the flame makes a part of the arc between the two coatings, the flask is entirely discharged, without the arms of the person who forms part of the arc experiencing the least shock.
EXPERIMENT II.
I adapted to the summit of the pile a circular brass vessel, containing spirit of wine. By these means the pile was made to terminate in a strong flame, to which I applied a metallic conductor, while with the other hand I touched the bottom of the pile. The Galvanic fluid still withstood my efforts; and the case was the same when I substituted for the spirit of wine the flame of a common candle. It is proper here to remark, that the flame did not lessen the action of the Galvanism when the conductor, instead of being applied to the flame, was applied to the plate at the summit of the pile.
EXPERIMENT III.
I have already proved by a series of experiments, addressed to C. Lacepede, that flame made to form part of the arc applied to the nerves and muscles of a frog, prevents muscular contractions. I repeated the experiment, with the same result, on several warm-blooded animals. I observed that the flame interposed in the arc, which touched the back and belly of the torpedo, prevented the electric shocks.
PROPOSITION X.
_Certain fluids, applied to the whole surface of the pile, or of animal parts, do not prevent the action of Galvanism._
EXPERIMENT I.
Two years ago, I made various experiments on this subject at Florence, with the celebrated Fontana; and we found that a pile, composed of a hundred plates of zinc and silver, after being immersed some time in common water, still exercised a very strong action. Professor Fontana informs me, in a letter, that he has performed the same experiment several ways, and always with the same success.
EXPERIMENT II.
Being desirous to examine the nature of the element inhabited by the numerous family of fishes, which are also subject to the influence of the Galvanic processes, I filled with sea-water thirty earthen vessels; and having formed a communication between them, by means of heterogeneous arcs, composed of brass and zinc, I obtained a shock, which appeared to me stronger than that obtained with artificial salt water. By establishing an arc with only five of these vessels, the action was very sensible. A pile composed of pieces of pasteboard, moistened with sea-water, and entirely immersed in the same water, gave, when tried, very strong shocks.
EXPERIMENT III.
I was able to prove the action of the Galvanic pile and of metals under water, by the following simple experiment: I placed a plate of zinc at the bottom of a vessel filled with salt water, (Plate II. fig. 6.). A person then brought the spinal marrow of a frog into contact with the surface of the salt water; and another person, absolutely insulated, touched with a silvered copper wire the plate of zinc. Every time that the wire was brought into contact with the zinc, muscular contractions took place. I am well aware, that the advocates for metallic electricity will deduce from the plain statement of this fact, an induction contrary to Galvanism; but my candour, on this occasion, will show how much I am attached to the cause of truth.
EXPERIMENT IV.
Among animal bodies, the torpedo is one of those which produce the most powerful Galvanic action. In the autumn of 1801, I made some experiments on this animal at Genoa, in conjunction with Professor Mojon and his brother, who gave me every assistance in their power. When I touched the torpedo, under water, at the moment when it gave the shock, it contracted itself, and two jets of water proceeded from the two holes in its head. To obtain the shock, it was not necessary to touch two distinct parts of its body: in many cases, the application of the hand to the electric organ was sufficient.
PROPOSITION XI.
_Mere electrization, by means of the common kinds of apparatus, does not increase the action of Galvanism._
EXPERIMENT I.
Artificial electricity was communicated to an apparatus, composed of a hundred cups, care being first taken to insulate the table and the persons who were afterwards to receive the action of it. If we suppose that the heterogeneous arcs were charged with different kinds of electricity, it would seem that, by communicating to them any electricity, the electricity of the whole apparatus ought to have been reduced to the same kind; consequently that no shock ought to have been produced. The contrary, however, was the case. We experienced very strong shocks, very little different from those which would have been obtained without artificial electricity. I observed the same result with the pile.
EXPERIMENT II.
An insulated torpedo being electrified, the shocks it gave were not increased. The torpedo was killed, and then armed, according to the method of Galvani, for the purpose of trying whether metallic electricity, in this case, would have any influence over it. After this arrangement was made, every time that the conducting arc was applied to it strong contractions were produced; but very little different from those remarked in other animals. This observation is agreeable to those made at Naples by the celebrated Abilgaard, who, having subjected the torpedo to the Galvanic processes, found no extraordinary contractions.
PROPOSITION XII.
_The Galvanic action is increased by employing as part of the arc the apparatus of Volta, or the electrified Leyden flask._
EXPERIMENT I.
In the hall of the Institute, I placed on a large table a hundred glass cups, and arranged them in such a manner as to form two rectangles, each composed of fifty. I established a communication between the first of these cups and the apparatus of Volta, by means of a metallic wire, which proceeded from one of the interior chambers of the _Cabinet de Physique_, and terminated at the place where the experiment was performed. I then tried this arrangement several times; and, however different opinions might be in regard to the precise increase of the action of the Galvanism, all constantly agreed in considering the shock as stronger. Some even went so far as to assert that it was increased a third.
It gave me great satisfaction to be able, on this occasion, to confirm the last discovery of Professor Volta, as well as one of those which he had made before. One observation, well attested, which tends to establish the truth of this proposition, is, that if a person touch the summit and base of the pile with two large metallic conductors, the shocks he receives will be much stronger.
EXPERIMENT II.
Electricity, concentrated in the Leyden flask, contributes also to increase the action of Galvanism. Having prepared a pile, composed of fifty plates of copper and zinc, I formed an arc by interposing a charged jar, and obtained an explosion much stronger than that obtained by the Leyden flask charged with an equal quantity of the electric fluid, and discharged independently of the pile.
EXPERIMENT III.
I took the same flask, after it was discharged, and having formed a portion of an arc, applied to the two extremities of the pile, I observed that the Galvanism refused to pass the obstacle presented to it by the stratum of glass interposed between the two coatings; consequently I received no shock.
EXPERIMENT IV.
I repeated the second experiment, insulating the pile, and at the same time the person who touched the pile with the charged flask. By these means I obtained a much stronger explosion than could have been produced separately by the Leyden flask or the pile. In this experiment I observed that the repeated passage of the electricity of the flask throughout the whole extent of the pile, did not deprive it of the property of exciting Galvanism.
PROPOSITION XIII.
_Galvanism, in animals and in the pile, traverses large spaces with the same rapidity as the electric fluid._
EXPERIMENT.