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II
PART TWO
OUR NEW EXPERIMENTS ON ANIMAL ELECTRICITY
25. Such an important discovery could produce nothing but
great enthusiasm wherever this news arrived , and most of all among us, being a discovery
by an Italian scientist. And many competed to repeat the experiments. Encouraged by many
of my colleagues, especially CARMINATI
who kindly
lent me the GALVANI dissertation, and REZIA, who helped me with the groundwork, I was the first here in Pavia, and in Milan too a few days later,
towards the end of Lent.
But I must admit that, I began my first experiments incredulous and having
little hope of success, so surprising to me did the results look concerning the mentioned phenomena, and, if
they did not contradict, they far exceeded everything well known about
electricity.
I beg pardon to the author of the discovery for my scepticism and almost stubbornness, though I am not ashamed of it, and I take more care to praise him highly, now that I have seen for myself what I could not believe
previously.
In short,
since I became an eyewitness to and operator of those miracles, here I am,
converted and turned from incredulity to fanaticism.
26. I have been undertaking these experiments for little more than a month and I have already done many of them, extending and modifying them, not without obtaining new positive results and knowledge. But till now I
have kept experimenting on frogs, with which I obtained positive results, because the excitability property of muscles and even cut limbs lasts longer in these cold-blooded animals, i.e. for hours and hours, giving easier and reliable tests, towards the goal I settled myself in these first researches. Meanwhile, my colleagues and I were so keen to perform
tests also on warm-blooded animals that some of our best students undertook them and their success proved thoroughly the incredible discovery of Mr.
GALVANI.
As far as I know, these last experiments have not been much extended and changed, but only just to the amount that
appears sufficient to verify and confirm the existence of the same phenomena of animal and organic electricity, which can be found in frogs,
turtles, lizards, fish and other cold-blooded animals even in warm-blooded animals like dogs, cats, lambs, pigs and many other four-footed animals and
birds.
I will not therefore discuss these
experiments conducted by others, nor the few I have performed up to now using a lamb and a pigeon with the aid of Dr.
PALLETTA, an important surgeon and pathologist of Milan, and the assistance of Dr.
BARONIO and others, and for the second experiment, helped in my house by Dr.
VALLI Toscano(p) and some few friends as observers. I shall give you just a brief summary of other experiments which I performed on frogs with greater care and study and which, as already said, I have modified and extended for more specific
research.
Even skipping the detailed description of these experiments of mine, which would take too long, I
will confine myself to illustrating in brief the most important results and, especially those which offer something innovative or more detailed compared
with the work of Mr. GALVANI.
27. After verifying the basic experiments on
real animal electricity, proper to the organism itself, so that I have no more doubts about it, I devoted myself to studying its quantity, quality and way of functioning. And I decided that
study on the quantity or power of electricity was the most important, to be addressed first. And how could we obtain significant results if things cannot be reduced to measures and degrees, especially in Physics? How can the cause be evaluated if not only the quality but also the quantity and
intensity of the effect are determined? Now, in order to evaluate the quantity and power of the electricity
in the animal itself: i.e., the one which naturally acts in its organs when contractions and movements of its muscles are induced by a metallic conductor arc between muscles and nerves, first of all, I thought
it best to reduce the effects of artificial electricity on these organs and to determine the minimum of this electricity which is necessary to induce in this animal
– alive or dead, complete or cut to pieces, and prepared in different ways – as well as in its
severed limbs, muscular contractions and jerky movements like those produced in the same animal by its natural, spontaneous
electricity.
(p) This skilful young man, who
had already graduated in medicine, decided to continue his studies at our University.
He recently, i.e. on the 5th of April, published a letter on this subject, in which he discusses various experiments of his, some new or at least varied in different ways, and explains some ideas mostly from a medical rather than physical point of view, as he says, which might mature in the course of time but which actually
seem to us too improbable and still very obscure, as the experiments were performed in a
hurry and not sufficiently verified.
28.
Thus, I discovered that
weak electricity is sufficient to cause not only small motions and convulsions but a vigorous
trembling in all limbs, and especially the legs, and even a weaker one with frogs prepared
in the GALVANI way, with the legs attached to the spine (or only to a part of it) by its skinned
crural nerves, the rest of the body cut away and stabbed with a pin or a metal needle in the vertebral column, whether passing through the bone or inserted along the spinal
cord.
29. With this
preparation, electricity, so weak that it does not even produce a spark and which cannot be detected even by the
highly sensitive BENNET electrometer, causes strong convulsions and
jerking of the frog’s legs.
30. Therefore a frog
thus prepared looks like a perfect animal Electrometer – for as such it can be considered
– more sensitive than any other Electrometer, as it does not fail to give signs, and visible signs , in response to a charge, which does not even move the thinnest
gold-leaves in a Leyden flask. And the frog is not the only animal with a particular
aptitude to function as an electrometer. I have tested with equal or almost equal results on different small animals, such as lizards, salamanders, mice , suitably prepared The reason why the frog works better than all others lays in its strength and in the fact that it can be more
easily prepared in the prescribed way.
31.
Such unthinkably weak electricity that it does not reach 10 and sometimes even 5 hundredths of degree
on my straw Electrometer(q) suffices to produce the above- mentioned phenomena of
convulsions in the legs of the frog, provided that the electric fluid flows directly from the nerves to the muscles, i.e. when it enters from the former and goes to the internal substance of the muscles themselves. On the other hand, should it flow in the opposite direction, coming out of the nerves and reaching the outer surface of the muscle, those motions do not take place unless an electric
force at least fourfold, sometimes sixfold and eightfold, i.e. 20, 30, and more hundredths of
a degree on the same electrometer, is applied.
(q) The jar Electrometer of Mr.
CAVALLO, improved by SAUSSURE,
BENNET and, if I may be allowed
to say so, by myself also, is sufficiently well known. My main modification was to replace the thin silver strings, which ended with pieces of elder pith,
by two simple strips of straw which made the electrometer even more sensitive. Besides, this produces another considerable
advantage, viz. the shifting of the simple straw pendulums increases regularly according to the electrical intensity, so that it is double, triple, quadruple in presence of a double, triple, quadruplicate
intensity, etc.
A detailed description of this instrument is available in my first Letter on Electric Meteorology, Vol. 1 of the Physics Series of Dr. BRUGNATELLI.
Mr. BENNET, at about the same time, i.e. in 1787, replaced the straw strings with two extremely thin gold leaves, obtaining the advantage of making the Electrometer even more sensitive (V. le Trans. Filos., Vol.
LXXVII, 1787).
32. The reader might wonder how I manage to measure and assess this imperceptible electricity i.e. very small charges of the Leyden jar, lower than
one degree, even 1/4 and 1/10 of a degree. Well, my answer is that I can easily do this with the aid of my electricity condenser,
an instrument that I described at length in a specific dissertation(r), and
which has helped me on many occasions to detect and measure electricity which could not be detected and measured in any other way.
33. Coming now to think about the great facility of the muscles to contract themselves, i.e. using less electric power, when we have positive electricity in the nerves that penetrate the muscles and
negative in the external parts of the muscles, rather than proceeding in the reverse direction, I must say that this has demonstrated
to me that the electricity of the organ itself, which generally acts on the simple application of a conducting
arc, if it is to be considered as a feeble charge from a Leyden Jar, must be negative on the nerve side, i.e. in the internal part of the muscle where it is connected, and positive on the external side, so that the electric fluid flows from the latter to the former, i.e. from the outside to the inside, in that spontaneous and natural discharge, and not from the inside to the outside, as in Mr. GALVANI’s opinion.
(r) The above-mentioned Memoir, in which I describe this invention of the condenser, has been presented at the Royal Society in London and then an abstract
was published in the Trans. of Philos, 1782, entitled "Concerning the way to sense the weakest Electricity (natural or
artificial)". Afterwards, I improved the apparatus and discovered a very useful device, which is obtained by covering the hand with a special waxed or painted taffeta glove and , so dressed, keeping it applied to the upper surface of the Electrometer while touching it with a Leyden Jar charged
to an extremely low degree. This is a very useful method for detecting and measuring
imperceptible electric charges and that is what I detailed in the
afore-mentioned Lett. 1st (previous note). I also explained there how I can calculate the fraction of the electricity condensation I obtain with any normal condenser, and in particularly with this latest glove
condenser.
In
Cart. Volt. K 20 ß, p. 22 of the Ms. the note
continues: i.e. showing that, for example, by touching the Electrometer cap with the hook of the jar, weakly charged with 10 or 12 sparks of a small
Electrophorus, this reads 1 or 2 degrees, whereas if I should touch it while keeping
it covered with a waxed glove as I explained and then withdraw the Leyden jar and immediately afterwards the hand, the same electrometer would read up to 100, 200 degrees, if such high measures were possible. Therefore, if one charges the Leyden Jar with only one of those sparks and then adjusts the level of
electricity to 1/10 of a degree only, by means of a very precise electrometer, as is that with
gold foil, so that if one operates in the described fashion, this electricity, which
would otherwise be immeasurable, becomes perceptible and visible, reaching up to more or less 10 degrees
on the same electrometer. In this way I can evaluate, with a small margin of error, the level of the charge in a jar to be
so many hundredths of degrees, which is what the electrometer reads after such a procedure.
34. As I have said, natural electricity, implying an
imbalance of fluid between the nerve and the corresponding muscle, or between its inside and outside, can be described as a special type of weakly-charged Leyden
flask or at least it seems it may be considered such. In fact, Mr GALVANI considered it exactly in this way and, at the very beginning, we did too. But, at the moment, many new experiments (some of which I
will explain later) lead us to consider the matter either from one or another point of view, but anyway far from the idea of similarity with the
Leyden Jar: I will briefly discuss some of these new ideas in a while, intending to elaborate and reconsider them
maybe in another dissertation, if further experiments and new results should convince me.
35. Whether we confirm or not the correspondence with the Leyden
Flask, after having verified the fact, as I did in many tests with this aim and in many different ways, that we need much less electric power to produce convulsions and muscle
movement if the electric fluid flows from the nerves to the internal part of the muscles than if it flows from the nerves to the
outside of the muscles, there will always be a marked difference in the electric state of the nerve
relative to the muscle, or from its inner part relative to the outer part. This condition, whatever it
be, acts so that the nerve, or the internal side of the muscle, tends to collect and invite the electric fluid to enter, while the external part of the muscle tends to reject it. With this we mean that both parts conspire to induce
the discharge of a conductor or flask, when positive electricity is applied to the nerve and the negative to the muscle, so that
a weaker charge is enough, if compared to what happens in the opposite direction
where, instead of an attraction, we have a double opposition of the nerve which prefers receiving instead of giving, and of the muscle which prefers
to give rather than receive.
36.
Now, if by way of the electric fluid, these muscle contractions and voluntary movements can be produced even in a living, whole animal, as
everything leads us to believe, and if, as should also be assumed, these are obtained in the easiest possible way, it must be because the said fluid is driven from the brain to the muscles by way of the nerves, thus employing
minimum force, rather than by pushing it upwards, though even in this way the same movements can take place provided more power is employed, i.e. a faster and more abundant quantity of the electric fluid is used. But, no more of this for
now.
37. Let is pass,
however, to other no less interesting observations.
The great number of tests I
have performed on cut and dissected frogs, alive or dead, and after hours or days,
have given me occasion to make several observations and reflections on the, if I may
say, electrical vitality of these and other animals. As time is running short, I must omit for now many minor details and summarise what I believe I can state, i.e. that 4 degrees or well separated states are encountered in passing from suspended animation to complete death: and each one of these death levels or phases has a wide
time scale.
38. So
this is the situation: my observations have taught me to distinguish four degrees or stages of death, each one well defined and
long drawn out. The first is the asphyxia, or suspended animation, and the last, the fourth, is what I call plenary death, which borders on decomposition. The other two stages, the second
and the third, maintain different degrees of surviving vitality for a long time; the second one has so much vitality that, just by applying the proper metallic
armatures, and keeping them in contact, one can produce muscle movements, initially vigorous and then progressively less strong. This happens because the animal electricity still
lasts even in cut limbs for a while. As soon as this natural, inborn electricity dies away or becomes insensitive, we enter the third stage of death where we can still produce the same motion of the muscles, this time exciting them with artificial electricity, of which a low intensity is initially sufficient and progressively more power must be applied until not even the strong discharge
from a Leyden Jar can move them. It is precisely at this point that they are dead
in the fourth degree.
39. I would dwell on the matter too long if I were to detail the difference between these steps and how to recognise them, and how likely it is to recall to life an animal at the second or third
stage, with our present-day knowledge or with new attempts we could make. Therefore I aim to relate and explain my idea on these subjects in my next
Memoir.
I just want to say at the moment, that this gradual progress in the steps of
death is slower than what is currently thought, and each distinct and defined stage has such a wide range of degrees that it usually lasts for a long time, though it is not always in the same way though, since many causes may effect this behaviour.
40. First of all, the
diverse nature of animals makes much difference and in particular their being cold-blooded or warm-blooded. In fact, in
animals of this second type life is much longer.
Moreover, in the same animal group and category, there are species provided
with greater vitality than others; and, in the same species, single individuals vary depending on the age, structure and strength.
41. But what has more effect on the short or long duration of each phase is the type of death suffered by the animal, i.e. the cause of death and especially if death comes quickly or slowly.
42. I
have done many experiments on this subject, and I propose to do many more, i.e. concerning the intensity and duration of each stage of the surviving
life force, I have examined many frogs some of which I let die of pain and privation, some immersed in
more or less hot water, some with severe wounds and all sorts of mutilations, some with repeated electric shocks and others with just
one very strong one. I have written down these experiments in a Journal that I shall make public as soon I have extended these experiments, as I
intend to do, to other types of death on these and other kinds of animals using foul airs and vapours(s), and different poisons.
43. For the time being, I
shall finish this short essay, with which I wanted to present you the most relevant experiments on animal electricity I have made until now, by saying that, even without uncovering the nerves, without any cut or wound, I can stimulate in an animal not only alive but sound and intact, without using any external electricity but employing only its natural inborn electricity, just by applying suitable electric
armatures, I can stimulate at wish convulsions, muscular spasms and tremors which are obtained using the same GALVANI process with skinned and insulated nerves or any similar scientific preparation. As a matter of fact, by applying my method, the contractions can be generated all over
any animal part according to the position of the armatures, etc.
44. To give you an idea of these experiments, I tie up a frog or fix it to a plank or a table with two or three pins or I have its legs held by an assistant, without hurting it, then I cover any part of its body ( the best parts are the back or the
lumbar region) using a piece of lead or a tin foil ("silver" foil, in those
booklets used by gilders, works very well), and I apply to another part of the frog (e.g.the legs or
thighs) either to the upper or lower side, a key, a silver coin, the handle of a spoon, any plate made of any other metal but lead or tin. Finally I bring these two
armatures into contact either by shifting the mobile one till I can touch the side of the other one, or
by using a third piece of metal, e.g. a brass wire functioning as a conducting arc. And here is my frog having convulsions in
almost every part of its body, maybe more in some parts and less in others, vibrating the muscles of its legs one by one, kicking
and jumping.
(s) Regarding the exhalations, I have only just started testing on three
frogs asphyxiated using sulphur vapours which were extremely effective in eliminating with life any residual vital sign, since asphyxia is directly followed by total death; so, the signs of
natural animal electricity end in a few minutes, and after a few more there is complete insensitivity to artificial electricity however strong.
45. And so, depending on the position of the
armature on the animal’s body, the muscles of the belly, legs, neck or head convulse, shake more
and more, and the spine itself leans as if stricken by tetanus.
46. These new experiments on whole, undamaged animals –
which are probably more remarkable and, in many respects, certainly more instructive than any other experiment we performed cutting limbs and skinning a nerve, etc., as, in this way, we can somehow study the natural behaviour of animal electricity in a living, healthy and undamaged animal
– brought to my mind new ideas regarding the slow motion of electric fluid, like a flow or an oscillation, or something else (that I still
do not venture to guess) between muscles and nerves, and any other solid or fluid part of the body, as all parts are more or less good conductors though not perfect nor comparable to metals.
47. Assuming then that the electric fluid is in continuous flow, whatever
that is, through every part of a living animal, and through its organs even if severed,
as long as any sign of life persists; assuming that the fluid moves as an effect of the organisation of the organs and of the vital
forces, continually unbalancing in quantity or tension in some parts with respect to
others, e.g. between nerves and muscles, or between their internal and external parts, which automatically try to balance themselves as an effect of their elasticity, in such a way that the fluid flows through other parts like membranes, vessels, humours, in such a way and quantity depending on which kind of connection is allowed between the parts. For this reason I think we must consider the
tranquillity of the animal i.e. muscles are not intended always to be moving; they
must have a break, so they cannot modify the natural, balanced motion of the electric fluid, unless we invert the flow itself or we speed it up, or just in case two much fluid arrives in this or another part of the body.
Should that happen, it could cause a twist in these muscles into which the fluid
irrupts with extraordinary strength.
48. As I said before, there are two different elements that might disturb this regular flow, causing variation or modification of the normal motion, whatever
that is, of the electric fluid inside animal organs themselves: viz. internal and external
facto
49.
The internal ones can be reduced as follows:
1st to the action of the will, increasing, decreasing, stopping or inverting the flow of fluid towards those parts in which it intends to excite movement.
2nd to accidental, abnormal causes, which here or there increase or decrease the ability to conduct, making certain parts, for example, more or less penetrable to humours and the humours themselves more or less dense, saline, oily, etc. As a result the conducting capacity changes so that the electric fluid is forced to flow faster an more abundantly through some of these conductors, because the passage is restricted etc.
50.
The external causes are due
1st to the action of artificial electricity, whose discharge forces electricity to flow away from its normal place in one or other part of the animal. This refers to all the experiments to excite convulsions by means of sparks or artificial electrical discharges.
2nd Applying separately two metal armatures, of whatever size, and then making them connect. This is what we are dealing with here.
51.
So, going on with my ideas: I easily understood that applying such armatures and a conducting arc would make more electric fluid move faster from one part to another in the body thus armed. However, if the movement of the fluid transferring itself from one place to another naturally tends to be in no wise slow, and yet it fails to move the voluntary muscles of motion. That is why this tendency to move is not basically great – indeed it is very small – and must push the electric fluid through the intervening insufficiently perfect conductors, viz. animal substances: muscles, nerves membranes, humours, none of which, as I have said, is comparable to metals. But this is what we want: suitable armatures should move sufficient electric fluid freely and fast enough to convulse the muscles thus invaded. The situation is this: the whole trick is to cause instantaneous transfer of more copious electric fluid. The fluid anyway moves from one place to another within the animal but distributes itself unhurriedly, without any other help, through all the conducting parts. Instantaneous transfer is caused by exterior application of much better metal conductors over a fairly wide area, at least one band width, and by using a conducting arc, preferably of metal, to join both the armatures. If part, even only a small part, of the arc is not metal but not a bad conductor, even water, we need do nothing more. The reason is clear: water is far from being as good a conductor as metal; it happens to be no better than juicy animal parts, so there is no point in conveying from some other part of the animal to there, where the armatures are, any more liquid at greater speed than is normally done by the natural internal conduits: membranes, vessels, humours, etc. However, a metal arc is needed which is not interrupted, even by water, to effect such rapid transport of electric fluid as to occasion the convulsions with which we are
dealing.(t) 52.
As I said, it was because I had this idea that I conducted these new experiments on whole, live animals, with the results stated. I experimented not only with frogs but also with eels and other fish, lizards, salamanders, serpents and, what’s more, with small warm-blooded animals, like mice and birds – these, though, I had to skin partially, in order to succeed. I have no doubt I will also succeed with bigger animals, which will be the more surprising the closer their internal, if not external, structure resembles that of man.(u)
End of first Memoir
EDITORIAL BOARD NOTES
AND ADDITIONS FROM A. VOLTA’S MANUSCRIPTS
[1] In Cart. Volt (Volta File) J 84 α, there is a piece dealing with the same subject. It cannot, however, be established with certainty, that it was contemporaneous with this text.
[2] In ms. K 20 β (Letter to Vassalli), V. gives 24 March as the date he began this experiment. The date is confirmed in the Journal of Experiments J 2 α quoted in §42.
[3] At this point in ms. K 20 β , which appears to be a previous draft, there is a detailed account of experiments to study the effect of electrical discharges from conductors and Leyden jars on more or less fully prepared frogs but the results are only briefly mentioned. Here follows the interesting part of ms. K 20 β:
When just a mediocre spark directly strikes a muscle, it greatly irritates it and sends it into convulsions. The muscle also reacts, even if the spark hurts it not, when the spark strikes the head of a conductor and sets electric fluid flowing through a series of other conductors so disposed as to include the muscle as a connecting link. These facts, as I have said, have been known for some time. But there is more. What struck me as new and surprising is that such a weak electrical charge, which cannot even manage to raise the slightest spark, should be capable of exciting the same movements and convulsions. The only thing required is that the charge should be from a big enough conductor, no, better, from a Leyden flask. This is small but has the capacity of a rather big conductor, as is well-known(*). It is also necessary that this electrical flow, which is a very weak charge, should pass entirely or principally through the nerves to the muscles, or vice versa, as will be proved by what follows.
What above all might seem wonderful – and certainly it seemed so to Mr. GALVANI – was that even a sizeable electric conductor placed directly on the frog laid on a table, or via other conductors, and several feet away from the electric conductor could not raise a spark, yet the discharge, via other routes, gave birth to convulsions in the frog. It can certainly not be said that this electricity from the conductor can transfer itself as far as the frog which is several feet away, because the capacity can only raise a spark at a distance of one or two inches, and only a very tiny spark at a distance of over three or four. And when a small portion of it arrives, it is during the time the conductor remains
electrified and not at the moment of discharge, and the fluid takes an entirely different route than that leading to the frog. So how does it manage to convulse at that very moment? This question would have been embarrassing a few years ago when we knew not of electrical atmospheres and what we call pressure electricity, but nowadays it is known and the explanation is easy and obvious. An electrified conductor spreads around its sphere of activity a force which tries to move the electric fluid proper to all bodies within its ambit. This atmosphere is far more extensive than the range of electrical transmission. It pushes the electric fluid characteristic of bodies in its area from the most immersed part of the conductors to further away, and indeed to parts outside its atmosphere, if this electricity is positive or in excess. The opposite happens and it draws the fluid nearer from far away to the most immersed parts if the electricity is negative or lacking. Then when the discharge from the conductor takes place, causing a spark, and its electrical atmosphere is removed, the fluid returns to its proper place. If the discharge is instantaneous, so also must the return flow be instantaneous and takes place along the route of the best conductors. The discharge becomes visible if on the table over which is the electrified conductor there are various other metallic conductors (the last of which extensively touches the floor) all connected to each other apart from very slight interstices in one or two places, so that little sparks may appear at these gaps however intercalated with cardboard, wood, or whatever other conducting body less deferent than metal. Should it not become visible etc.(l)
To tell the truth, I cannot yet indicate the precise amount of weak electricity required to convulse the muscles of a whole live animal nor how otherwise weak it should be to cause the effect on a prepared frog cut up and laid out as previously indicated. It is per se indeterminable, since it depends on the differing strength and disposition of said animal, whether it has been well or improperly prepared, recently or some time ago, the ambient temperature, etc. Generally, though, what I can say about it may be seen in the following
results.
1.
Starting with an entire, live frog, quite weak electricity makes it convulse greatly, especially its hind legs, if we direct the discharge or the electric fluid from the head to the feet or vice versa. For example, a charge of 10, 12, or 15 degrees on a HENLY electrometer or a quadrant electrometer from a 6,8 or 10-foot long conductor is sufficient. Very little is necessary, I repeat, and it is not even essential that the conductors, between which the frog is placed to form a link, be insulated; they can also be laid on a wooden or marble table, or on the floor. Since the electricity is discharged all at once, the electric fluid chooses its own speed, mostly passing along the route of the best conductors, i.e. the metal ones, and little along the less deferent wood, stone, etc. In any case, as the current is divided, it is better that the frog and the conductors conveying the electricity be insulated, since in this case the discharging electric fluid is carried along all together and that much weaker electricity is required to obtain the effects indicated. If instead of a simple conductor we use a LEYDEN flask, because of its greater capacity this will produce the effect, viz, the frog’s legs shaking, with only 4° or 5° on said quadrant electrometer, when the animal is in the circuit or arc conducting the discharge, with communication being established as already stated, the frog’s head being on one side and its legs on the other.
2.
The frog being decapitated and a long needle inserted into the spine, an even smaller charge is required, like 4° or 6° from the big conductor and only 1 or 2 from the Leyden jar, as shown on the above electrometer, the discharge being directed from backbone to feet or vice versa.
3.
The whole body of the frog being cut away, leaving only one hind leg attached to the spinal cord or part thereof by one crural nerve what is required is incomparably much weaker electricity. This cannot even raise a spark and is not visible on the quadrant electrometer, but only on the extremely sensitive CAVALLO bottle electrometer made even more sensitive by BENNETT, and not always on that. This produces the usual effects, indeed even more lively contractions of muscles, tonic convulsions and violent spasms.
4.
Finally when the trunk section of spine and (even better) also a portion of nerve are covered with metal foil, the leg muscles react strangely to electricity which is even imperceptible to the above electrometers, a Leyden flask charge of barely 1/10° on my extremely fine straw electrometer. To register this and somehow calculate it, one needs to use my condenser of electricity.
The following section is most notably among V’s first doubts about animal electricity. It appears logically to fit here but it has been impossible to establish its actual place in the Ms. (Cart. Volt, J 12 α).
All this fits with the ideas we have about the influence of nerves and it is easy to understand. What is not easy, and for which I have not yet been able to find an even moderately satisfactory reason, is why we need armatures that are dissimilar. And how is it that it is so useful to have one of the armatures perfect, i.e. adhering well, as if stuck on, and of so little use, indeed harmful, if the other is also? It is so detrimental that no, or hardly any, effect occurs. In other words, no convulsions occur when two such perfect armatures are brought into contact with each other. And how on earth are we to understand that an imperfect one is more successful if we want merely to transfer electric fluid from one part of the animal to another? I mean that if both are imperfect they should function badly, but, if both are perfect i.e. if both metal foils are thin and adhere well, they function worse still. This is staggering and difficult to believe. Whether we believe or not, the fact is that – at least in whole animals, or only skinned ones. Otherwise, if completely prepared so that only the bare nerves remain somewhat isolated, as practised by Mr. GALVANI,
then, whatever the metal armature attached to nerve or muscle, as long as there is some vital force left in the animal, forgetting about the armatures but with only contact from the conducting arc, convulsions occur, as we have already noted( )(l) . As I was saying, that is the situation when the nerves remain covered. In other words, such is the influence of these similar or dissimilar armatures that the effects, the usual movements and convulsions, are obtained by applying them both to similar parts of the animal, i.e. both to muscles, indeed both to companion muscles, e.g. the gastrocnemius muscle in both legs, or even to two parts of the same muscle, provided the armatures are different; rather than applying two similar armatures to different parts of the animal, as it might be one to the spinal column, the other to a leg muscle, which are the best places, given the connection between nerves and muscles, as we have seen above ( )
(l)..
Now, reflecting on all this doubts sometimes arise in my mind as to whether metal conductors, dissimilar or applied differently to two places on the animal, could not of their own accord, when brought into contact with one another, give life to the electric fluid, which then naturally transfers itself from one place to another, as apparently we should believe. I wonder, in a word, if they are not merely passive instead of active agents moving the animal’s electric fluid from its post, and from tranquil equilibrium, thus disturbing the balance and forcing the fluid to enter one way by one armature and leave by the other in another manner. Such a suspicion cannot help but be formed when we see convulsions – and strong convulsions at that – in the frog’s legs, on connecting the little tin strip, attached to part of a thigh, with the silver coin placed at a corresponding position on the other thigh, by means of a conducting wire. Here there is no reason for which the electric fluid should tend to transfer itself from this thigh to that or from that to this. Indeed we see nothing happening if both the armatures are similar, or two coins or two strips of foil. If, then, convulsions occur, and therefore we have evidence of electric current, i.e. fluid, moving from one thigh to the other, when the foil is applied to one and a coin to the other, we must conclude that it all comes about because of the armatures. It is the difference in how they are applied, more or less precisely, or in whether they are smoother or rougher, more or less flexible, etc., that causes the imbalance of electric fluid at the points of contact. In short, it happens to a lesser extent but it happens and it is through rubbing that artificial electricity is caused. That is where we can observe different metals, and even the same metal, rubbing against the body, giving it their fluid – or taking, according to the greater or lesser pressure of rubbing, more or less heat, flexibility, roughness or smoothness of the metal strips. If we reflect about this some more, rubbing properly speaking is not even necessary, since any blow, knock, and even slight pressure is enough in favourable circumstances…
Revised and completed by John Coggan, Oxford University
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