SECOND MEMOIR
ON ANIMAL ELECTRICITY
§ 1.In the previous Discourse I confined myself exclusively to giving an outline of the various, numerous experiments I carried out on the both new and interesting subject which is Animal electricity, within the two months that followed my
entry into this charming field which was opened to us by D. GALVANI’s great discovery. For this reason, having done nothing more than
enunciate in general the main results, I now think that it is opportune to go into
more detailed description. My first researches referred, as I have already mentioned (see Memoir I, § 1), to the establishment of the minimum artificial electricity which might be necessary to cause in frogs and other small animals convulsions and similar movements that might be observed as a result of their own innate electricity. For this reason, and considering how such researches had to
illuminate the way that led to the others that I could carry out on such animal or organic electricity, I thought it
was expedient to put the former before the latter. It is therefore my intention to give now, first of all, a short report on those which actually concern the weak artificial electricity applied to the above-mentioned small animals, frogs, lizards, mice, etc., but, in particular, to
frogs.
§ 2. I began to experiment with
the effect of artificial electricity upon frogs, holding one of them in
one hand by a leg or one of its hind feet or by its head and hurting different parts of its body with sparks sometimes
from the conductor of an ordinary electric machine, other times with sparks coming from the shield of an "electrophorus"; and finally, with sparks which became weaker and weaker until they reached the lowest level of force powerful enough to cause convulsions and a general tremor in the whole of its body. I then came to the other minimum level which provoked only
the slightest convulsions or throbbing of any of the muscles or muscle fibres. Now, the smallest spark visible in broad daylight
but which was large enough to cause a slight crackling, produced if not the first effect
(that is to say the afore-mentioned convulsions and jerking throughout the whole body) the second one which caused contractions and partial trembling; and actually, it took a little more
power to obtain the first result.
§ 3. It is not even necessary to
strike directly any part of the animal with such weak sparks, since it is enough that they are given off between the electrified conductor and another metal which might communicate directly with the body of the frog, or thanks to the interposition of a third
or fourth one, etc., until, summing up all of them, the frog will be placed somehow as a link
in a chain which binds these conductors all together, so that the electric current can pass through it once
again.
§ 4. It is not required, either, that such conductors, placed in series with the frog in between,
be kept insulated. In fact they can all lie on the table or on the floor, and, despite this, every spark will substantially shake the frog, causing
sudden, impetuous contractions or stretching of its legs, above all
when it is placed between the conductors so that it can create a connection touching some of them with a foot, others with its head or with the other foot. This will be the result when the sparks
are given off at a distance of two notches from the conductor of the machine, against a metal ball, for instance, that is
at the head of the above-mentioned sequence of conductors, or at a distance
of one notch and sometimes even less than that when therefore the result will be
very weak.
§ 5. I explained that it is not a necessary detail to keep both the conductors and the frog
insulated. They can, on the contrary, lie on the table or anywhere else, provided that they are kept in a continuous
sequence. The reason for this is that the electric current, no matter how
weak or powerful it is, follows mainly the line of the best conductors, since it is naturally led to transfuse instantly, in the same way as in the
sudden discharges. Moreover, part of it flows at the same time also in the other conductors which are of an inferior quality, such as the table itself or other not very dry kinds of wood, the floor, etc. For this reason it always takes a
somewhat stronger discharge to cause convulsions in the frog which is put between the metal conductors or other sufficiently good ones, whenever both the conductors themselves and the animal are not
insulated. However, even in the case that all the conductors are actually
insulated, they have to be in contact with the ground to provoke better and complete
discharging.
§ 6. It is, therefore, advantageous to keep the metal conductors
insulated, upon which the electricity from the conductor of the machine is discharged, and to keep the frog at their extremities insulated
but in contact with other conductors which are similarly good, such as a steel wire or a chain generously prolonged onto the
ground.
§ 7. Nevertheless, more than anything else, the discharge
from a Leyden flask can shake our frog. This is because, given the fact that the electricity
from a simple conductor has to be strong enough to cause at least a
moderate or feeble spark, in the case of a Leyden jar it is sufficient to have a charge which is so weak that it does not
even manage to spark. In this case it is also not necessary either to touch the frog
directly with the hook of said jar or to create any form of insulation. In any case, the only requirement is to place the animal within the
circuit of the discharge or to make it part of the conducting arc.
§ 8. Actually, it is surprising to see
in what manner and how much it is shaken by such extremely feeble and non-sparking discharges
from flasks which might be also very small. The wonder, moreover, decreases only if you think of how the charge of Leyden
flasks, at a certain degree of the electrometer, is equivalent, as regards the amount of electric current and thanks to their
so great capacity, to a charge of the same degree from a simple conductor which is hundreds of times as big as they
are(a).
§ 9. However, though the amount of electric fluid
accumulated in a jar a few inches thick is always small, and once
added to the discharge by means of a metal conducting arc it does not show the smallest spark,
it being possible only to explore and measure its weak strength through the most precise electrometers, such charge is nevertheless sufficient to cause convulsions in the
frog.
§ 10. Up to now we have used for our experiments
a live, intact frog. Should it be first disembowelled and cut in such a way that its legs remain connected to the backbone just by means of the crural nerves, that is to say following GALVANI’s way, then its legs will contract and leap
for even weaker electricity. This reaction will be caused even
by non- sparking electricity (produced by a quite capable conductor) and
by the charge from a Leyden flask that hardly manages to move by a degree or even less my thin
straw electrometer. The reason for such sensitivity is that every flow of electric current has to pass
all together through the narrow duct of the bare, insulated crural
nerves.
§ 11. Now, therefore, we are not looking for anything more than an extremely small flow of electric fluid which invades the body of the little animal, in particular its nerves, and which passes through them quickly in order to cause in the muscles the above- mentioned convulsions. I underline that it is important that all the process
must take place quickly, because if such flowing is delayed by bad conductors, the effect might be lacking. That small but fast flow
which passes through the body of the frog is obtained by means of the also extremely feeble discharge
from a Leyden flask, which does not produce a spark, as you know, and which sometimes does not
even move a precise electrometer. It is obtained by a sparking discharge as well as by a feeble and occasionally
non-sparking one from a simple conductor, passing such discharges
directly or through other conductors placed over the frog’s body, as has been shown
so far.
§ 12. There is, however, another way
in which we can obtain the same result and which we cannot ignore. The effect is obtained also by causing a great spark from a rather big, wide conductor, even if its electricity has a totally different direction from
that of the conductors between which the frog is placed. A man, for example, when exposed to a great spark from the conductor of the electric machine is shaken by its passing down to his feet through which the whole discharged electric current passes to the ground, while at the same time the frog lies on the table,
many feet away from the mentioned electrified conductor touching or staying close to some other good, non-electric and non-insulated conductor which is extended to the ground. Now, the frog itself also shakes and has convulsions
at the moment in which the man attracts upon himself the electricity of the big conductor
from the machine.
§ 13. Why does this happen and how? And is the flow of electric current small or great that all of a sudden invades the frog’s body and goes through it?
The answer is easy when you know the action of the electric atmospheres, that it is the current which moved and withdrew from the conductors that were subject to the electrified one, i.e. plunged into its very extended field of action. Such current flows back to where it came from, following the same
route, that is to say, through the series of conductors lying on the table etc., and among which the frog is placed. It flows back
at the moment when such pushing atmosphere is destroyed by a great spark from any part of the electric conductor, which consequently comes to be completely, or almost
completely, discharged.
§ 14. It would be useless to spend more time
explaining the effects of such electricity, which is precisely called
Pressure Electricity, and to apply them to the case we are considering. Those who know the theory, in fact, do not need to be told, while it would take too long to explain everything from the start to those who do not know anything about
these effects. This is one of the fundamental laws concerning electricity, on which most phenomena depend. With just this law and with a proper application of the
action of electric atmospheres, the charge and discharge of the insulating plates, the property of the tips, the laws of electric
movement, the activity of the "electrophorus", the condenser, etc., can
all be properly explained, as I have already shown in numerous dissertations
published in various journals(b), and as many others have shown. In particular, the
reflux phenomenon of electric current in conductors submitted to the action of the atmospheres, even from far away, has been clarified for the most part by Mylord Mahon(c). He shows how you can be violently shaken and even killed by this,
which he calls the returning stroke.
§ 15. It should not be surprising, then, that the frog moves once it is placed on the table, close to whichever non-insulated conductor and various feet far from the electrified conductor of the machine, when a quite powerful spark is obtained from this latter which is discharged in
any other direction whatever. The effect is the utmost then, if such electric conductor is very big and placed above the table itself. In this case, if the electricity is extremely powerful and discharges suddenly with a full spark, small sparks will appear between one metal conductor and another lying on
said table, or between one of them and the frog which are not quite contiguous. Those small sparks clearly show the electric current
flowing back, as has been underlined. However, since a current even inferior to the one that can cause a visible spark is enough to shake the frog (see § 7 and following para.) when, coming from sufficiently powerful conductors, it suddenly brings a fairly good quantity of current; and since an even
comparatively small current is enough to produce the effect, i.e. to make the legs of the frog
jerk after the animal has been disembowelled and cut so that its legs are connected to the trunk only by means of the crural nerves (§ 10),
then, especially in this case, to cause convulsions in the animal, there is no need, either of such powerful discharge
from the electrified conductor or of such great closeness to the conductor and the frog which are placed on the table. It is sufficient that they are not outside the field of action, which consistently extends beyond the distance
to which the spark might leap. If indeed the spark can be stimulated, for instance between two big metal balls, placed at a distance of only a
little more than one inch, the acting electric atmosphere would go to 2, 3, 4 feet and beyond, according to the conductor’s width and power.
§ 16. Now it is possible to see how the experiments described in the 1st and
2nd parts of Mr. GALVANI’s works, and outlined in the first two
tables(d), are no longer surprising. The only admirable aspect is the great sensitivity of the frog, above all when it is prepared according to GALVANI’s way, and of other small animals, to the electric impulse which causes convulsions in their limbs when a small quantity of electric current that does not even produce a spark, goes through them, especially through their
nerves.
§ 17.Bigger animals are as sensitive or almost as sensitive as small ones. If they are not shaken in such a way that their muscles
(and the entire body of small animals) are evidently convulsed by such
a small flow of electric current causing contractions in the muscles, it is because such current spreads too much in the large body of those big animals. It takes the several different directions
offered by the many fibres, vessels and humours. In little animals, such small quantity of electric current is obliged to flow through those few deferent fibres it meets and therefore it affects them, causing more irritation where the duct is narrower. We have already noticed such an effect (§ 10) in the little animals in which the flow of electric current is forced to go just through the main nerves, once they are left bare, insulated and deprived of the muscles (like
the crural nerves of the frog). Besides, if we cut from any big animal a portion of any muscle which is useless for voluntary movement, the
gluteus, for example, cutting quite a long portion of it but not longer than a frog’s leg, we will see how such
a piece of muscle will have spasmodic contractions caused by the same, extremely weak electricity that is passed through it.
§ 18. I am still talking about
the flow of electric fluid, in particular of the instant or at least very quick flowing of a small or rather very small quantity of such current, which
always causes great convulsions and movement whenever it enters the nerves and the muscle fibres, but especially the
former. This is because, otherwise, if the electric current does not enter
that circle which allows it to go through the nerves or muscles, and instead it accumulates in various amounts or disperses in them, it will not produce those effects. So, if a whole or prepared frog is put on the conductor
from the electric machine and thereby gets the most powerful electricity, it will remain quiet until any spark is produced or,
should the electricity become too strong, an intense electric jet comes out from a part of its body, for instance
from the extremity of a hanging leg. The same thing happens if we put the frog on the shield of the "electrophorus", raising and lowering it in turn; every approach and removal
changes the condition and electric tension of the shield, and consequently of the frog placed on it. The result is again the same when the frog is exposed to the air of a room which is so highly impregnated with electricity that the little pendulums of a
CAVALLO electrometer bump against the inner surface of the jar,
etc..
§ 19. So the electric condition which might be
more or less powerful, i.e. the redundancy or scarcity of electric current in the entire body, any
stagnant electricity, or (as we can say) of simple bath, does not affect our extremely sensitive little animal. It is not affected at least when the purpose is to stimulate the sensitivity of the nerves or the irritability
of the muscles in order to produce in them the contractions that are obtained whenever the electric current, even in a small quantity, flows and goes through
them.
§ 20. Considering these experiments, it is possible to see clearly that the influence that such electric condition of the atmosphere has on the animal
economy(e), at least
as far as muscular movements are concerned, is very little or even absent. Therefore we have also to expect very little from the practice of applying artificial, simple bath electricity for curing diseases. In order to obtain any effective result, the electric current must be made to pass, instantly or by shocks, throughout the entire animal, directing its
flow so that it affects nerves and fibres etc., using other known methods of
medical electricity. Moreover, we must confess that, despite all its previous and present supporters, this latter has not made
the progress it seemed to promise(f).
§ 21. Going back to our frog, that shakes entirely,
especially its legs, whenever a small amount of electric current passes in a moment from the ground to its feet or vice versa (an amount that is extremely small when all the current is forced to pass through the crural nerves which are the only connection between the legs themselves and the backbone (§ 10)), I must admit that I was not satisfied with all the approximate experiments that I have described until now. I wished then, to determine more accurately and precisely
what degree of electric force could be sufficient to cause strong or weak convulsions in the frog, when it is submitted to different approaches during different forms of the experiment. I wanted to reduce such force to measures and degrees which could be compared, using suitable
electrometers or the condenser, when electrometers alone no longer register the too feeble charge. I actually wanted to employ any useful means. This is why I
used the small, simple apparatus that I shortly am going to describe(g).
§ 22. It consists of two little columns or crystal tubes that are more or less six inches long and fixed to a small board. They both have on top a cap made of cork, or any other softwood, so that it is possible to easily thrust the frog, lizard, etc., into them with two hat-pins in the desired way. Usually I fix the animal by its head or by one of its front legs on the one side and by one of its feet on the other side. In this way the other hind leg hangs down between the two little glass columns and it leaps when the electric discharge passes through the body of the frog and
subsequently all its limbs have convulsions, also those ones that are far from the main direction of the current. At times, instead, I fix both its feet together;
at other times one foot here and one foot there, so that the trunk of the animal, with
its head, hangs down, etc..
§ 23. When the frog is fixed in such a way to the gallows, it is properly
insulated, and the entire, weak or powerful, flow of electric current, which will be discharged upon the animal, is forced to pass through its body without dividing itself through other conductors. The result is that a smaller charge of electricity is sufficient to cause convulsions of the limbs it affects, as we have already observed (§ 5). It is true that, in comparison to the body of the animal which is full of humours in all its parts, fairly dry wood is so scarcely conducting, that very little would be lost if the frog were fixed on a small board which were a bit moist or wet, and nothing would be lost in the case such small boards were well dried. However, since a certain degree of precision is required, it is more proper and safer to maintain perfect insulation with the two glass tubes in the way that has just been described.
§ 24. Besides, this small apparatus is actually useful in any way you wish to employ it in order to infuse electricity and make it go through the body of the little animal. Do you wish to discharge upon it an entire Leyden flask? It is sufficient to incline
the jar until its exterior armature (its belly) touches the top of one hat-pin and its hook the other hat-pin. Do you wish to experiment once again
on the discharge from a simple conductor? Take in your hands the small board and keeping a finger in contact with one of the hat-pins or a wire or a metal chain that hangs from it, bring the top of the other hat-pin under the electrified conductor until they touch each other
suddenly.
§ 25. Now, coming to what is more important, that is to say measuring exactly and bringing to comparable degrees, as we intended, the electric forces we employ, here is the remaining part of my apparatus. A cylindrical, silver-plated
wooden conductor, one inch in diameter and about two feet long, is fixed horizontally above another little glass column, which is about one foot high and encrusted with sealing wax and therefore properly insulated.
This conductor has on one of its ends a HENLY electrometer, i.e.
Quadrant-electrometer, among the most precise of this kind(h), which we will call
Quad. el. having to mention it very often.
§ 26. At the other end, when it is necessary, i.e. when electricity is so weak that the
Quad. el. does not show any sign of it, I make the top of a jar-shaped electrometer with little pendulums of thin
straw touch and stay united. 16 degrees of it correspond to one degree of the above mentioned
Quad. el.. I will call it Micro-electrometer and in order to shorten it, it will be written as
Micr. el..
§ 27. This jar-shaped electrometer,
Micr. el., is provided with a metallic pan screwed onto the top and destined to condense electricity there, by keeping applied to it with
one hand, while electricity itself spreads through it, a piece of oilcloth or painted taffeta that
is wrapped around the hand becoming a sort of glove(i). The degrees which come out on the
glove condenser by means of this artifice, which usually registers 50 degrees to one, will be called 1/50 of
a degree, or degrees of the Micro-electrometer condenser, which will be shortened as
gr. Micr. Cond..
§ 28. From this experiment it is possible to observe that since 16 degrees of the
Micr. el. (as we underlined in § 26.) correspond to one degree of the
Quad. el., about 800 degrees of the Micr. Cond. correspond also to one degree of the
Quad. el., i.e. one degree of the Micr. Cond. is equal to about 1/800 degree of the
Quad. el.. Therefore, when the charge, for example of a Leyden flask, is insensitive so that the simple
Micr. el. does not move even one degree, if we can obtain for example 4. 6. 8. 10. of the
Micr. Cond. through the mentioned artifice of my glove condenser (see previous §), the jar could be said to be charged with as many as 1/50 of degree of the
Micr. el. and 1/800 of the Quad. el..
§ 29. In order to give an idea, however, and to offer a term of comparison of the force that corresponds to the degrees of electricity in the above-mentioned instruments, I am first going to underline that, as regards the powerful charges, a few Leyden jars make my
Quad el. rise to 70 degrees. These 70 degrees (which are circle degrees) are to be considered equivalent to between as 85 and 90 degrees(l)
because of the
ever-increasing difficulty the pendulum has to rise after it has exceeded 40 degrees. Few jars can bear such
a powerful charge without spontaneously discharging or breaking
up. A charge of 40-50 such degrees in a flask which has an armature of 100 square inches, comes often to kill, or at least to stun, a lizard, a frog, a little mouse.
§ 30. As regards feeble and very feeble electricity, which is more suitable to our experiments, electricity that goes from 1 to 2 degrees of the
Quad. el. (i.e. 20-25 degrees of the Micr. el.) is required in order to obtain from the only two feet long simple conductor, the weakest spark that does not even crackle, is not excitable from any considerable distance but only by means of contact with a metal and is visible only in the dark. If the conductor were much bigger, 10 degrees of the
Micr. el. or even less than this would be enough to cause a small spark.
§ 31. So, as for the charge of Leyden flasks, two degrees, or even just one degree of the
Micr. el. or even less than that, are sufficient according to whether the jar is more capacious. A small flask, which I use most of the
time, with an armature of 12 square inches, must be charged with 2-3 degrees of the
Micr. el. in order to produce, touching an entirely metal conducting arc, such small
a spark that I can hardly see in the dark. It is not enough to have a charge of less than 2 degrees.
§ 32. Such a feeble charge that hardly moves the little pendulums of the Micro-electrometer and that barely attracts a very thin linen thread or a bit of a
small gold foil from a close distance, does not cause the slightest sensation on the tip of my nose, the tip of my tongue
or an eyelid when I touch them with the hook of the flask I hold in my hand. It takes a charge that is
double this, i.e. of at least 4 degrees of the Micr. el., in order to make
me feel a light and hardly perceptible stabbing pain.
§ 33. So, what incredible weakness should the charges have when they cannot even be registered by the
Micr. el. unless we make use of the artifice of the condenser; and using this does not guarantee more than 4, 6, 8 degrees of the
Micr. Cond. which correspond to 1/50 of degree of the simple Micr. el., and to 1/800 of the
Quad. el. (§ 27, 28)? Nevertheless we have already indicated (§ 7) and we will show more clearly that less than this, i.e.
charges of only two degrees on the Micr. Cond., are sufficient to cause contractions and spasms in the muscles of a frog which has been prepared following Mr. Galvani’s
method. Namely its legs have to be connected to a part of the backbone by means of just the crural nerves and the animal must hang from the gallows by the backbone itself or the nerves on one side and by one or both its legs on the other side. It takes only two degrees
on the Micr. Cond, as I was saying, if the discharge is brought from the nerves to
these muscles, because otherwise it would take much more than that.
§ 34. This is what I thought needed stating beforehand about the degrees or measures of electricity, in order to be clearly understood in the description of my experiments, so that others who repeat them could obtain the same results, referring to the equally determined degrees. To avoid
being boring, I will here recount a few experiments only. I will describe just those in which I
noted the circumstances more diligently and took more accurate
note of the fixed degrees of electrical force that were employed. I wish to act like this since the other innumerable experiments I
performed about the same topic have given results that were, if not totally similar, very little different. I will
talk about how I used some frogs for the experiments which were once alive and healthy, once suffering, entire, beheaded, with perforated or lacerated spine, or torn in another way. I made them suffer these pains and preparations sometimes
shortly before submitting them to the electrical experiments, at other times many hours before and
yet other times as much as one day before the experiments. So after I had prepared them entire or cut into parts, and submitted them to artificial electricity that could be getting weaker and weaker or stronger and stronger, I passed to
preparing them by baring the crural nerves but leaving them connected to the legs and cutting all the rest, except sometimes for part of the spine, which on other occasions I cut away completely. Once I had prepared them in this way, I again tried to discover not only what the slightest
amount of electricity was, sufficient to cause convulsions in the
leg muscles, but also if and to what degree they gave signs of their own innate animal or spontaneous electricity. As I was saying, I prepared and treated my frogs in
numerous ways. So, choosing an example among the many similar experiments, I will offer for every different way, an instance of the results, which all the other analogous ones more or less agree with.
§ 35. Starting therefore, from the frogs which are full of strength and life, which have not been mutilated nor torn in advance, they are violently shaken in all their body by a little spark
from the cylindrical conductor (see § 25) that has been electrified with 10 degrees
on the Quad. el.. Small animals also react with a slight convulsion in the legs through
electricity of 6-8 degrees and a bit for an electric current of 4 or 5 degrees as well. It
matters not then that the electricity from the conductor exceed or
lack in quantity and that the charge follow a direction from head to toe or vice versa or even from one foot to the other. On the contrary, since the frog shows its body hanging from the gallows with one leg here and the other there, 3 degrees only
on the Quad. el. produce some effects, as do even less than that, corresponding to less than 30 degrees
on the Micr. el.(m)
§ 36. Once the head of the frog has been cut off and the hat-pin has been fixed in the spine, things happen more or less as if the head had not been cut away. If there is any difference between the two conditions, then it can be found in causing convulsions with
somewhat smaller electric force.
§ 37. With an extremely small Leyden flask, i.e. with an armature of just 3 square inches (but which has a 10 or 12 times as big capacity as the
afore-mentioned simple conductor has), four or six times weaker electricity is sufficient, that is to say a charge of 5 or 6 degrees
on the Micr. el..
§ 38. With a flask of 12 square inches, a charge of 2 or 3 degrees
on the same Micr. el. is enough.
§ 39. With bigger flasks, it is possible to gain further, but
not much, since, using a jar of 30 square inches of armature, it took, if not the indicated 2 or 3 degrees
on the same Micr. el., more than 10 degrees to cause convulsions in the whole frog and one degree or a little less was necessary with a jar of 96 square inches.
§ 40. I must not forget to point out to you that the little convulsions are sometimes stimulated only in the toes; other times in some muscle fibres of the thighs. Those
somewhat more violent and produced by a slightly bigger amount of electricity, act throughout the entire leg that shakes and
jerks; and afterwards they come to affect finally also the other parts of the body, and the spine which arches, etc..
§ 41. Furthermore, in general, the sensitivity is equal both in the entire or simply beheaded frog and in a frog which has been
annihilated by passing a long needle through its spine and its legs as well, which
have been separated from the rest of the body. Such sensitivity keeps itself to the same degree, or almost to the same degree, for about an hour after such mutilations. In this way, during all this time, 10
Quad. el. degrees of the simple conductor are always sufficient to produce great convulsions and 5 or 6 degrees cause small ones (see § 35). The charge of 5 or 6 degrees
on the Micr. el. 2-3 from the extremely small flask and that of
Micr. el. 2-3 degrees from the jar with an armature of 12 square inches (see § 37 and 38) have the same effects.
§ 42. Using such a jar, which is still included among the small ones, a charge so weak that hardly produces (as we have already seen in § 31 and 32) an extremely small spark, which does not crackle at all, does not reach any considerable distance and is visible only in the dark Such a
charge is sufficient to cause contractions in the entire or mutilated frog, or just in the cut legs, once its feet have been fixed separately to the gallows. This charge, however,
it must be said, requires immediate contact with the metal conducting arc. It barely attracts a very light thread and scarcely moves a bit of the
thinnest of gold foil. In fact, it does not produce the slightest stabbing pain in the eyelids, on the tip of the nose, etc.. Such feeble electricity actually surprises
one by the great effect it produces in both the live and dead limbs of our little animal. It is nothing yet if we compare it to the far weaker
electricity which causes the same or even more remarkable convulsions, when the frog is prepared according to Mr. GALVANI’s
method.
§ 43. Once it has been cut so that its legs are attached to a piece of the spine exclusively by the crural nerves, 2
Micr. el. degrees only, or at the most 3 degrees, and not from Leyden flasks but
from the simple conductor, are sufficient to cause not very feeble convulsions in the small animal (see § 25). If we employ the flask with the 12
inch armature instead, the charge of just 1 degree on the same
Micr. el. is enough to produce violent convulsions in the legs and to stimulate shocks, etc.. Lower degrees, i.e. 15/50 or 16/50 of degree, calculated by means of the
glove condenser, and which I call 16 degrees Micr. Cond, produce
the same results as well (see § 24).
§ 44. Such an amount of electricity
suffices if the discharge, i.e. the flow of electric current, is directed from the spine, that is to say from the nerves to the legs or vice versa. There is more to say, however. If the direction goes from the spine to the legs, then the convulsions are caused by an electric force that is 4, 6, 8 times weaker than before, i.e. of 2 or 3
Micr. Cond. degrees, using the flask, and 2-3 of the simple Micr. el., if no
charged flask is employed but exclusively the conductor (see § 25).
§ 45. I have already described in a short paper addressed to Dr.
BARONIO(n) and in the previous Discourse or Memoir(o)
what consequences can be deduced from this observation that has
now been confirmed by the numerous experiments I carried out with as much accuracy as possible, regarding the far weaker electric force which is required to cause convulsions
when direction is given to the current. I do not think therefore that it is necessary to add more about this matter.
§ 46. We will rather go back to what deserves great consideration. I am talking of how an inconceivably small electric force, a charge
from a Leyden flask 40 or 50 times weaker than that which comes when touching metal, can produce a very slight spark which is hardly visible in the dark; that is at least 20 times as little as that that registered just one degree
on my very sensitive, extremely thin-straw electrometer. It is such a feeble charge that it does not even move the highly precise BENNET electroscope with strips of very thin gold
foil, but it is nevertheless sufficient to cause convulsions in the legs of the frog which has been prepared
in the way described.
§ 47. This animal electrometer, which can really be named like that, beats all
other electrometers, no matter how sensitive and precise they are, in giving signs of very weak charges. Whenever, in fact, the charge of a jar might seem absent, even measuring it by means of the above-mentioned BENNET
electroscope (and only the condenser could register signs of it), it will be detected from the contraction or shaking it causes in the prepared frog.
§ 48. If such artificial electricity, which is so weak that no electrometer can register it, can affect the organs of the animal so much, then it is not at all difficult to think that the same effect may be produced, i.e. the contractions and the muscular movements, by the organs’ innate electricity which is equally feeble and with such weak tension that it does not
manage to move the most sensitive of the afore-mentioned electrometers.
§ 49. Actually such great electricity, a disproportion of electric current among the parts of the animal sufficient to move our electrometers, could not in any way exist
because of the conducting quality of the fibres themselves, of the vessels and humours of the animal itself. Nature has, however, provided the nerves with such and so much sensitivity, the muscles with such and so much irritability that an electric force,
which is otherwise imperceptible, is sufficient to cause the mentioned contractions and muscular movements. A similar phenomenon,
which could be useful as an example, can be found in light. If it
be, in fact, that it does not have sufficient mechanical moment
to produce the slightest, perceivable impulse, to move, for instance, a feather or
other extremely light object which is touched by it, it in any case stimulates the optic nerve remarkably. It then
damages this latter by means of its too powerful effect and in the same way,
even a feeble, rarefied light can not insignificantly stimulate the optic nerve. Now, it is therefore not
surprising, that a small, weak flow of this other ethereal current, which is very thin and, as we can say, similar to
lightp, as electric current is, stimulates and excites other nerves
on touching them. They can be as delicate as such a flow (I will
say more about this first case afterwards) or a bit less delicate than that and, from the excitement produced of the nerves, there come the contractions and movements of the muscles from the dependent ones [1].
§ 50. But, does the electric current
instantaneously act on the nerves and not on the muscles? Will its action be restricted to stimulating the
nerves exclusively, since it passes through such and such a limb of the animal with a force that is completely insensitive to the most precise electrometers? This is what brought me to think a lot of new experiments I carried out. In a while I will
talk about them. I will show how the primary effect of the electric current, when it circulates in such a way, involves
nervous action in the experiment. The consequences or rather the real effects of
this action are the movements of the voluntary muscles.
§ 51. Therefore, we agree with the best physiologists about the fact that these movements and
others, but in particular the spontaneous ones, depend, in the first instance, on the action or influence of the nerves. If we stop here for a moment, however, we can see that it might seem that we have taken a step forward with the studies of our electric current, with this animal electricity we are dealing with. Nevertheless, we have
certainly not achieved as much as the first experiments had promised. It is true that we have discovered in this current the direct agent
which exactly stimulates the sensitivity of the nerves – actually a remarkable
result but not sufficient. We wanted to go beyond and we thought we had
done so. We felt namely sure that the electric current itself moved the muscles, i.e. through its own stimulating property, causing their contractions and movements. Now, having to restrict its field of action, attributing to it just influence on the nerves, how
behind are we in comparison to what we thought we had achieved? We understand and somehow explain the primary stimulation of the nerves, or
rather, we know where it comes from, but then the way in which it originates and sets the muscular force in motion is still an unsolved problem as it was before.
§ 52. I repeat, we thought we had solved
the problem, or at least remarkably cleared up a topic which is a puzzle to
physiologists. They had been obliged, in fact, to stop in front of such incomprehensible action or influence of the nerves on the muscles. They could not
manage to explain what process or medium allows the passage of stimulus from one end that is far
away and slightly stimulated, through the entire nerve up to its extreme ramifications; and how, passing afterwards to the muscles, it excites their very remarkable contractions. We had taken the liberty of believing that we could explain this through our electric current flowing from the nerves to the muscles and exciting them directly. Even though, in general, physiologists themselves considered
excitability as an innate and typical force of the muscles, they also used an intermediate agent, or whatever medium, through which the influence of the nerves on the muscles could pass and act. At this point they gave way to hypotheses. Some of them involved only the solid parts of the nerve in the experiments, and conceived of vibrations and shakings which could
spread from one end to the other; others (and these were and still are nowadays in the majority) thought of a certain slight fluid, which they named
animal Spiritus and to which they gave a double function: it had to carry the effects of the external objects along the direction of the nerves towards the common sensorial centre; and it had to flow, according to the
impulse of will, through the nerves towards the muscles and to excite their movements. Now, here
is the most important step we thought we had taken before the discovery of animal electricity: following Mr. GALVANI’s ideas,
the author of this great discovery, we thought we had come to understand through which medium and how the command of the nerves acts on the muscles or what, at least, such
a nerve current was, since it was supposed to be called animal Spiritus. That was the electric current, and we assumed that its main function, going from its own typical conducting nerves to the muscles, was to act
directly on them as their proper and natural stimulator. How could this phenomenon be explained? However, the more plausible and seductive explanations together with those that seem to be in conformity
with the first general appearances, are seldom corroborated by more precise and
careful examination of every single phenomenon. When an important discovery occurs, it seems to us that we can go far beyond by applying it to great and magnificent matters, but then we are often forced to go back and give up most of the projects we had conceived(q). This happened in the present case, as well. Once I had examined the matter by changing the experiments and carrying out some new ones,
I was obliged to realise in the end that the action of electric current in the organs of animals is much more limited than GALVANI, and I with him,
had supposed it to be, since its direct influence ends in the nerves, as I have already observed above (§ 50).
§ 53. I do not wish to deny that it can act on them
directly and, by irritating them, can cause contractions and movements.
Powerful electricity, a lively, stinging spark, that strikes the muscle, can and has to do this, like every other stimulus. However, in this case the matter is
very weak electricity, as animal electricity is, undetectable to the most precise electrometers, which slightly affects only the nerves, since it is not sufficient to irritate
directly the muscles. Then the nerves bring their action onto the muscles in a way that we do not know yet.
§ 54. If this electricity acts
thus, it will not be even necessary for such electric current to enter the muscles themselves causing convulsions. Actually, it is sufficient that its passage
be restricted to part of the nerve or nerves which support and dominate such muscles. Now, numerous experiments have demonstrated that this is enough and here I will mention just a few of the more representative ones.
§ 55. Once the leg of a big frog has been prepared, so that its nerve, which has been well uncovered and detached from the spine, comes out from the thigh for all its entire length, I cover its end with a metal sheet which is folded around it or I tighten it with a pair of pliers. I apply the same treatment to another part of the same nerve, a bit below, i.e. I bind it with another small ring-shaped strip of a metal and I tighten it with another pair of pliers, leaving an interval of two notches between one armature and the other. In this way, below the
lower one there is still a portion of bare nerve and a small portion of
bare nerve is also in the middle. Once I have accomplished this, I discharge an extremely weakly charged Leyden flask; i.e. not sparking or just weakly sparking, over the two armatures that have been applied to the nerve, so that only the portion included between the two armatures enters the
charged circuit. Now all the muscles of the leg have strong convulsions and the leg jumps up and
jerks, although, as has been clearly shown, the flow of electric current is restricted only to the nerve or even to a small part of it, and the muscles and the whole leg are completely excluded. It is therefore not necessary
for such flow to reach the muscles, and that the stimulating electric current invade them. It is enough that it
tickle and stimulate the nerves which the muscles which are liable to voluntary movement directly depend upon.
§ 56. I repeated this experiment
many times, on warm-blooded animals as well, since it is easier to obtain with them the above-described effects, which, in this case, are also more valuable. After the big thigh
sciatic nerve of a lamb has been uncovered and cleared by all its surrounding contacts and cut two or three inches above its connection into the thigh muscles, I apply two round strips of
metal foil or sheet. One is placed close to the cut end and the other is put a few notches or an inch below. I can also choose to tighten it with pairs of pliers in the two spots mentioned which might be also very close to one another, avoiding
contact, though. So, once the nerve has been prepared and holding it up by a silken or other thread, avoiding
contact with the nearby parts, I make a weak electric discharge go through the small part of it, that is placed between the two metal armatures. This electric discharge, as you can see, does not reach the muscles of the legs; it does not affect even the other part of the nerve which continues to be bare between the lower armature and the insertion of such nerve into the thigh. Nevertheless, it once again causes convulsions
in the leg which shakes entirely, as if a Leyden jar were discharged by applying one armature to the leg itself and the other one to the nerve.
§ 57. I repeated these experiments and changed them in various ways, considering, however, the same event. I had the opportunity to notice that, keeping all
other elements equal, the convulsions of the limb that has been
severed from the trunk are stronger than when the body is left intact and the nerve has been prepared in its own place. This is true when the nerve that we prepare is the sciatic one in
quadrupeds and the crural or the brachial ones in frogs.
§ 58. What we have now shown to take place using artificial electric charges
is that even if current acts only in a few spots and within a restricted part of the nerve, there
is contraction and movement of the muscles which are distant but still obeying
said nerve. This also happens with the discharges or transports of electric current which are not produced by any previous artificial charge, but which go through the animal from head to toe, thanks to the simple application of proper armatures and
a conducting arc. That is to say that if the action is brought onto the nerves alone, or rather onto a small portion of the nerve section, the movements of muscles that are connected to such nerves, answer to this, even if the actual electric current does not
arrive at said muscles at all. Discover and isolate the crural nerves of a frog, the sciatic nerve of a lamb, etc., and, as described above (§ 55, 56), apply to two more or less near parts of the nerve itself, the two metal armatures, one made of a leaf of tin and the other made of brass or, better, of silver (we will soon see how important it is that they consist of different metals). Put them in contact, either through a third metal or
even, without the latter, by making them get closer one to the other until they meet.
At that precise moment convulsions and tremors will be caused over the whole limb which, however, is not affected and to which not even the smallest effect of the electric current can come, since this current goes just from one part to the other, and these parts of the nerve are near to one another.
§ 59. It is not very comprehensible
either, how this electric current moves from one place to the other, remaining so close to the nerve, thanks only to the application of
said armatures and their external contact; nor is it clear why
the armatures have to be dissimilar. This is however something that can be proved by means of direct experiments which we will
talk about on another proper occasion.
§ 60. In the meantime we can observe that there is no need either for both
armatures to be applied expressly to the nerve. One of them is sufficient, for instance a tin sheet, provided that it touch the edge of the end of the conducting arc, for example with a brass wire or another metal that is different from the one of
the armature, such as a golden or silver coin, a spoon, etc.. They should meet on the edge in order that the metal or conducting arc
touch at the same time both the flap, i.e. part of the armature, and some of the points of the bare nerve; so that this becomes a sort of equivalent of the two above-mentioned
dissimilar armatures one close to the other (see previous §). Mr. GALVANI has also noticed this effect, i.e. that convulsions are more easily stimulated if the flap of the armature is touched, together with some points of the bare section, by a metal wire. He found a totally different reason for that. The one we present here, however, bringing everything back to the not yet well understood
interplay of dissimilar armatures, but which has been concretely proved in every way, is the only one consistent with a lot of other experiments of
like kind, as will be shown better hereafter. If we take it into consideration, an enormous amount of phenomena and events which seem inexplicable, a lot of apparent anomalies can be explained, i.e. can be brought back to precise laws.
§ 61. Going back to the extreme
ease with which the nerves, and the nerves alone, are profoundly stimulated by any small flow of electric current that invades them, we now understand better why, once the frog has been prepared
in to Mr. GALVANI’s way, i.e. with the properly uncovered crural nerves
being left as the only communication between the legs and spine, it reacts so much and the legs convulse because of prodigiously feeble electricity which can be both artificial and typical of animals. This happens, for instance, with a Leyden
flask charge that can come to 2/50 or 3/50 of a degree on my electrometer with thin straws (§ 44); while, if the animal is left
complete, the muscles of the legs hardly contract with a charge that is 50 times as powerful as before, i.e. of 2 or 3 degrees
on the indicated electrometer (§ 38). As far as the leg muscles
are concerned, they too are invested in the same way by the flow of the electric current that passes through until it reaches the extremities of the feet both in the
event that the frog is complete and has been prepared in the afore-mentioned way. What does it matter in fact, if the legs are connected to the backbone exclusively by the crural nerves? Does the whole flow not pass finally through such muscles? On the contrary, it is plausible that it passes through more rapidly when the animal is complete than when, once the crural nerves alone are the only means of contact between the backbone and the legs, the
forced passage consists of just these narrow ducts which cannot but delay it,
as these ducts not perfectly deferent. For this reason, indeed, passing exclusively through the narrow nerve ducts with
some difficulty, the electric current bumps into them. In this way, it stimulates them more deeply than it would if such ducts were not the only passages, if other deferent ducts, muscles, membranes, vessels, humours had not been removed, if, to cut a long story short, both the loins and the stomach of the frog had been kept with all its bowels and integument. In this case, in fact, the electric current would flow along
in very many directions and the quantity that would affect the crural nerves would be much smaller.
Because they were in fact wrapped up within numerous other parts, they would be much less stimulated and not more considerably,
unless by a proportionally bigger electric force were used.
§ 62. This, too, leads us to think that the stimulating action of the electric current acts
primarily on the nerves which are assailed by its flow. The secondary
effect of the stimulation of the nerves is the movement of the muscles which depend on them (§ 50). Besides the already indicated proofs, various other arguments, which are the result of new experiments and discoveries of ours and which we will not talk about yet, contribute to support our thesis. It is namely different from the one of Mr. GALVANI, which we had actually adopted at first, and it rather concerns the electric current as the proper stimulator of the muscles, the immediate exciter of their irritability.
§ 63. You may object to me perhaps that the other experiments of mine which
were already indicated towards the end of my previous memoir (Mem. I, § 43
et seq.), with which I cause convulsions and tremblings in all the limbs of the entire, intact animal by applying exclusively the proper metal armatures and establishing communication between these two, indirectly or
directly, without uncovering the nerves, without taking away its integument and sometimes without even cutting its skin. In this case it seems that the electric current acts directly upon the muscles rather than on the nerves, moving from one part to the other. Above all, it is possible to observe that the experiment is carried out more successfully, i.e. the convulsions and the muscular movements are much more intense, if the armatures are applied to the strongest muscles and if these muscles have been uncovered in order to apply them directly.
§ 64. Are there not nerve ramifications in each of such muscles? Can they avoid the so- called electric stabbing pain? I have just shown (§ 55
et seq.) that whenever a small electric current goes through and stimulates a section of bare nerve, without muscular fibre, the section of
said nerve causes the convulsions and movements of the limb it affects, even if such current does not get to the muscles of the limb
in question. However, I dare anybody to prove that such a flow of electric current does not hurt any of the
afore-mentioned nerve ducts which extend through a muscle wherever it enters that muscle or even just a part of it. If it is not possible to
demonstrate this, my theory which shows that the nerves are what get excited by the flowing electric current, is, in any case, still true and firm.
§ 65. Besides, there is more. While you, who object to such experiments of mine and support the direct action of the
aforesaid current upon muscle fibres, cannot reduce the matter to the point that since it hurts these fibres and causes the contraction, its direct action is evident and immediate, the result of this position is that there will always be at least a doubt about whether a feeble electric current, like the one we are talking of, can achieve such
a result. While you support this theory, as I was saying, I keep on
making direct experiments (I propose to tell you about the latest one of them), and I will make
the flow of electric current perceptible and evident
to you, perceptible to your own organs (let us say it shortly!),
perceptible to the tongue and also the nerves since it is they that actually feel. Together with the flow of
electric current which gushes out in the shape of a small pennon and
produces the well-known fresh breeze on the top of the electrified conductors, I will obtain the same effect as above, also with the other invisible flow of the
very current that is obtained simply by applying the proper metal armatures which will then be
brought into contact. Through no other artifice than this, that is applying to the tip of the tongue
some tin or polished, clean lead foil, and placing a gold or silver coin, a silver spatula or
spoon in the middle of the tongue itself, then if you make the tin or lead
foil, against which the tip of your tongue rests, touch the shank of this spoon or of the spatula, or rather the coin, you will
experience the same sour taste that you usually taste on your tongue whenever you
put it in the slight breeze of an artificially electrified conductor at such
a distance that no sparks crackle. So, also in this case, the flowing of the electric current, caused throughout the whole tongue by the simple application of two metals and the communication established between the two metals themselves, excites the very same sensation, the same acid taste that is not weak but rather remarkable. No contraction will be caused, no other movement in the tongue itself that is however mobile and irritable. This is enough to prove that the nerve papillae, and not the muscular fibres of the tongue itself, are those which are directly affected in both cases by the electric
current, which, penetrating into them, softly tickles and stimulates them.
§ 66. So, this is the result. In these experiments the
sense nerves and not the movement nerves, which are not present on the tip and in the front part of the tongue, are stimulated by the electric current. However, the tongue is affected by the sense of taste; no convulsions and movements are caused, even though the tongue could be susceptible of them, and this happens thanks to the action of other nerves which are planted in its root. So, in order to excite such movements and contractions of the muscular fibres of the tongue, I immediately thought that it would have been better to concentrate the electric action upon that part. Consequently I obtained the expected convulsions after I had made the experiment of pulling out the whole tongue of a lamb and reinforcing one of its main root
nerves with an armature, then applying another armature towards the middle of the tongue itself and bringing them together again by means of a conducting arc.
§ 67. So, it is evident that, for each stimulated nerve and its precise function, there is a corresponding effect that comes from it, i.e. of sensation and movement, when
this feature of the nerves is set in motion by the electric current
involved. Therefore, the movement of the muscles, their contractions, etc. are a direct effect of this nerve action and not of the electric current, as we have already intended to demonstrate from § 50 until now and as all our next experiments will more substantially confirm. If the muscles had a reaction, if the small flowing of electric current, which we are talking about, could instantaneously irritate them, then why should such muscles not have convulsions caused by the tickling of that weak flow of electric current, since they are susceptible of convulsions and movements? Why should they not
convulse even when nerves are not present or, in particular, the nerves that Nature has destined to cause their movements? Well, the answer is that
that feeble current which we are describing (since we do not intend to discuss now the strong artificial discharges
that can produce sparks, etc. and that could, as we have already observed (§ 53), easily cause convulsions in the muscles, even without the
intermediary of the nerves), is sufficient to excite the sensitivity of the nerves in order to start their action.
Yet it is not sufficient by itself to excite the irritability of the muscles
which thus contract.
§ 68. Consequently, even when convulsions are stimulated together with more or less violent movements of the limbs of frogs and other
complete, live animals, both through very feeble artificial electric discharges, as we described at the beginning of this Memoir and through the simple application of proper metal armatures, and communication is established between them, as we observed at the end of the previous Memoir and also discussed once again here (§ 63), it is not the muscles, as I thought for some time, but it is the nerves spread inside the muscles and hidden by them that are primarily affected by the current. Moreover, the nerve strength
thus excited is what makes the muscles contract, as I assert now. However, you may observe how there is a correspondence between the spots, the
stronger or weaker intensity of these muscular movements, the greater or
smaller ease with which it is possible to excite them and the greater or
smaller closeness of the armatures to the nerves which sustain different limbs. In consequence, the skin and the other integument, even if they do not completely stop the experiments (and yet in some animals, i.e. quadrupeds, birds and others, they are such
an obstacle that it is absolutely better to take them away, at least partially, as I will explain
shortly), they affect the result negatively. And once this integument has been
removed so that the quick is uncovered, the convulsions of the muscles are never as strong and easily stimulated as they are by uncovering and
insulating the appropriate nerves according to GALVANI’s system, not even by means of the best armatures.
§ 69. It is not that the movements are not big enough and very often remarkable, also in animals that have been submitted complete to the experiments
following my new way. It is not even that it is difficult to obtain
movement; it is on the contrary extremely easy. Such experiments are easier if carried out in this way than following the usual way of Mr. GALVANI as regards preparation, since there is no need
for any dissecting of the animal, and they are more pleasant and fruitful as well. But as regards the ease of
getting muscle convulsions and the strength of the convulsions themselves, this method of mine is less effective than the previous one which involves uncovering the nerves. What deserves particular attention is that you have to look for four conditions in order to achieve a successful result
in the experiment when you leave the nerves covered, while you need
no such conditions once the nerves have been uncovered and insulated.
§ 70. The 1st condition is that the complete animal should be touched in two spots with no other conductors but metal ones. On the contrary, if a frog for instance has been prepared
so that its legs are connected to the backbone exclusively by means of the crural nerves, it is possible to excite convulsions at first, i.e. when there is fully vigorous vitality, by touching its feet with
one hand and the backbone or nerves with the other or with a more imperfect conductor such as wood, ivory, etc. as well.
§ 71. The 2nd condition is that such double metal contact should be applied to the complete animal, in both
places over a not very restricted area, that is that the two metal armatures must be applied properly. One armature could actually be sufficient, if the other is
replaced by the top of the conducting arc which must be large enough to touch in different spots. Now, such armatures or wide contact of the conducting arc are not necessary (even though they
may also be good) for the animal whose nerves have been uncovered, at least
while the animal itself keeps enough of its vitality.
§ 72. The 3rd condition is that the
afore-mentioned armatures should be of different metals, that is one should be made of tin or lead, the other of silver or gold, brass or iron. This diversity of metals is absolutely required. If both the armatures are made of the same metal, the way they are applied should be at least very different; for example, one could be silver
foil that adheres well and is almost glued to the part, while the other could be silver
foil as well but not so flexible, rather rough than smooth, like a coin etc.. It can be said that, for our purpose, in order to excite convulsions in the animal, the whole artifice consists of this: one armature could be of soft metal, i.e. lead or tin, and the other could be of any metal, though silver and gold give the best results and copper and iron do not work very well. In
an animal that has been prepared for the contact by uncovering its nerves, since no armature is absolutely necessary (see previous §), the usual movements and convulsions can be obtained by applying one or both armatures, which are made of the same metal and are perfectly identical, for instance two silver coins or two
pieces of tin foil, while the animal’s vital strength is not very weakened. When
its strength has grown feeble in fact, it is better also in this case to use armatures which are
dissimilar with regard to the types of metal or at least with respect to the
method of application(r).
§ 73. Finally, the 4th required condition is that the quick be not only directly touched exclusively by metal (§ 70), but by the whole metal conducting arc. If it is interrupted by a non-conductor or by a
bad conducting medium, like a thin sheet of paper or also a layer of water, which is a conductor, but much inferior to metals, the
convulsion effect is completely lacking over the whole animal, as we have already indicated and explained at the end of the previous Memoir.
Here the contractions and spasms are stimulated in the muscles, in which the nerves have been uncovered and prepared, even if a layer of water is placed in the middle of the conducting arc, or if a sheet of paper, cloth or simply moist leather are put in between, or even if one or more
people, the floor and tables enter the circuit, while, however, the vitality is fully vigorous, as we have already observed in the first prospect we presented concerning Mr. GALVANI’s experiments and ours as well(s).
§ 74. From all this it can be deduced easily enough how muscular contractions can be stimulated if the nerves relative to them are uncovered and insulated rather than
covered with flesh and other integument, including the skin of the whole, intact animal. As regards such skin and integument, I will have to show what
an obstacle they are to the appearance of the convulsions whenever we use the method we are discussing.
§ 75. I therefore extended these experiments to frogs, eels and other fish before using warm-blooded animals, since in the above-mentioned animals their integument does not usually
prevent the experiment giving good results, except if their skin is too dry. In this case it is sufficient to moisten it a bit. It is not the same for the quadrupeds and birds which I have been able to
test until now. With these animals, the experiment was carried out without success, having left their integument completely intact. However, I had to take away some parts of it, at least in those spots which I wanted to apply the armatures to. It seems therefore that the thickness of such integument, and its low conductivity, above all because of corpulence, are obstacles for that fast,
easy transport of electric current which is required to affect and stimulate the nerves, so that they can
subsequently cause contraction of the muscles; and it seems therefore, that such movements are missing until such integument is put between those muscles and their respective armatures. So it is better to take away the whole skin, or most of it, in the spots destined
for the armatures themselves. It is better to apply the metal surfaces to bare muscles, that is to say to the quick.
§ 76. The procedure I adopted that gave the best results
was to lance the skin of birds and quadrupeds(t)
all along their back,
turn it inside-out on both sides, and then cover the bare flesh with tin
foil; to lance and uncover some other muscle in the same way, for example, of a leg, and
to apply to it a coin or another silver plate. Once this has been done, the only thing required, in order to see the
resulting remarkable contractions, movements and jerking of that leg, is to produce a communication between
the two armatures, either directly through mutual contact or by means of a third metal.
§ 77. Also with salamanders and lizards, it was almost always better for me to skin them completely or partially. Without this procedure, with all the best armatures, the convulsions were either lacking or very little notable.
§ 78. In the case of frogs, even though we obtain stronger convulsions
much more easily when they are skinned, one can obtain the same effect, as I have already underlined (§ 75), by leaving them with all their entire, intact skin (which is very thin, moist and directly covers the muscles, which are even moister than the skin itself), if the tin foil is
particularly well applied and if we push quite heavily against the spot with the other armature, for instance the silver coin, wherever it is applied. The same result is obtained with snakes as well, at least with a snake which, in Italian, is popularly called
Smiroldo. I had the occasion to use a very big one of these snakes during my experiments.
§ 79. Fish too, upon which I carried out similar experiments,
gave reactions with their intact skin on. Once their scales had been scraped off, they
gave more remarkable reactions; but after I had taken away their skin, it did not seem to me that they gained a greater aptitude
for presenting contractions. On the contrary, it seemed that eels became less susceptible. Eels, covered with their own skin and provided with proper metal armatures [which have to be always
dissimilar, as has been previously explained (§ 72)], particularly when close to their tail, writhe and leap excellently at the moment when contact between the armatures is established.
§ 80. Now that we have considered all the required conditions and various more or less favourable circumstances
required for the success of experiments of this kind that purpose to cause convulsions in whatever alive, intact animal, such as frogs, eels etc., without any cut, not even of their skin, without uncovering their nerves, I would like to describe these experiments more precisely, in order that
anybody can repeat them easily and be sure of success. I take an intact eel and I apply to whatever part of its body an extremely thin tin
foil, i.e. of the kind prepared by gold-beaters and kept between the pages of certain books and which are used
as a fake silver coating. I apply this tin foil wherever I wish, to the head, back, stomach, flanks
or to the tail of the eel, choosing the length and width I prefer, so that it fits well, as if it were glued to the chosen point. After I have
coated the animal in this way or covered it with a well-fitting shirt of
chain mail, I lay it on its opposite, uncovered side onto a silver dish. Instead of the dish, a not very wide plate can be equally useful, such as a spoon
or a coin. It is better that this little plate be put under the eel so that it corresponds to the upper armature, that is to the adhering foil, or, at
least, so that it is not too far from it(u). After we have prepared everything in this way, it is sufficient to touch the silver dish or the lower silver plate and
at the same time the tin foil or coating worn by our eel, with a key, brass wire, another spoon or coin, in short with
any metal object whatever, provided that it is clean and neat. It is also sufficient, without any other intermediate metal
functioning as a conducting arc, to take care that the plate itself, or any spoon or coin,
replace the conducting arc, and we can do this by advancing and inclining it so that it touches the
afore-mentioned tin coating. In this way convulsions are instantly caused in the eel which wriggles, writhes, arches, rises and shakes its
fins, over the whole section of its body which is included between the
two ends of both armatures. It is interesting to observe how, if
this section includes the head or neck, the latter swells, the head rises and the mouth opens and shuts in turn, every time the indicated contact occurs. If the whole back or the
entire stomach of the eel, from its head to its tail, or an entire flank
is covered with an uninterrupted, closely adhering tin foil and if, moreover,
said eel lies with its bare side completely on a silver bowl, then at the moment in which
possible contact is made to occur between the lower and upper armatures, i.e. between the silver bowl and the tin foil, the whole animal has violent convulsions and
jerking.
§ 81. If we consider a frog, things are more or less the same. The tin cover can in fact be applied to the whole stomach or the whole back, or
partly both of them, or to one or the flank and it can be also applied to a thigh or a leg. For a frog, a big bowl is not
necessary. In any case, the silver plate, the spoon or the coin is sufficient. It is not even necessary to place these objects, as in the case of the eel,
either on the opposite side corresponding to the tin cover or close to it. If things are prepared like this however, convulsions and movements are actually more violent but also
when the coin or the shank of the spoon are placed on the same side, for instance on the feet or the thighs, and whenever either the loins or the back or the shoulders are covered with the tin foil, the
thigh muscles convulse and the legs shake at the moment when contact between the two armatures is established. So, even if a thigh or a leg wears a thin tin cover and the other thigh or the corresponding leg is in contact with the coin or the shank of the spoon, both legs will have convulsions and leap once contact has been
established.
§ 82. Because of these results the frog starts to differ from the eel. Even if the silver armature, which does not partially correspond to the adherent tin cover or foil and which is somewhat far from the latter, the same convulsions and spasms occur; and they are not just partial but, on the contrary, they affect the whole or almost the whole body.
§ 83. However, the biggest difference between the frog and the eel is that there is a more intense correspondence between muscles and nerves; and it acts in such a way that those muscles have more violent convulsions which have more
nerve connections, and they react when they are much closer to that part of the body to which an armature has been applied, while the other armature has been applied to other muscles. So, for instance, if the tin foil is applied and made
properly to adhere to the edge of the back and to the loins, i.e. where the thick crural nerves are situated only
just under the skin, then the legs will shake and jump, when also the
other armature, a silver plate or a coin (between which we are to establish a contact), is applied to the stomach, the chest
or the head. If said tin foil is glued onto the middle of the back, the muscles of the stomach and of the flanks will have violent spasms. If it is glued onto the shoulders, the reaction will affect the muscles of the chest, the front legs, the neck and the head. This will be the result whatever part the coin, the spoon or the silver plate are applied to.
§ 84. When I say that convulsions will occur above all in the muscles which are served by that nerve or those nerves which are close to one of the armatures, even though the other armature is applied to a totally different part, neither onto nor near
the muscles, I do not mean that the muscles which are directly covered with the armatures, and those which are nearby, are not affected. On the contrary, these muscles are usually the
ones that are affected most. Besides, in all or almost all the other muscles as well, it is possible to observe shakings,
jumping and spasmodic convulsions, if the frog is quite lively, if its skin has been taken away and if the tin foil armature is well applied to
a section of the backbone and all along this latter, since a lot of nerves ramify into all the other parts. Moreover, if every circumstance
determines the action on a certain limb, on certain muscles; if the silver plate touches or is near the same muscles which receive more nerves and more closely to the part of the body to which the tin foil is glued, if such cover, being placed, for instance on the loins, where there the crural nerves are, and if the coin, the silver spoon are on or under the thighs or the legs, if all these circumstances aim to achieve the greatest effect, then the most remarkable convulsions, leaps and prodigious
jumping of said legs will occur. Therefore, if an armature is applied on the spine and the other under the stomach, then the most violent, spasmodic convulsions will affect the stomach itself and the flanks. The same will happen in the
chest muscles or in the front legs if an armature is contiguous or nearby, etc.. It is amazing, moreover, to see how the spine itself arches backwards and the neck stretches out as well.
§ 85. You might deduce from what I have mentioned until now, that these experiments have been carried out in numerous ways. However, you will understand even better, if I say that I made further experiments with different pieces of tinfoil which had been applied at the same time to various parts of the
frog’s body. They were also separated by intervals of different
width. In this way they formed distinct armatures that were all equal and made of the same metal. I then placed the other armature made of a different metal, i.e. the coin, the spoon or even the silver plate, in contact with any of the parts of the bare side of the animal, and I tested all the
contact combinations, sometimes directly between the silver armature and any of those made of tin, and sometimes by means of a third metal which had the role of conducting arc. I sometimes applied five or six pieces of tin foil, one onto the head,
another onto the neck, the third to the shoulders, the fourth to the back, the fifth
above the sacrum and the sixth onto a thigh. Once I had placed the coin or the shank of a silver spoon, first under the chap and the throat, and applied
the end of a metal wire to such coin or spoon, I brought the other end once, twice, three times into contact with each of those separated covers or small shields of tin foil, in order to see which were the muscles that contracted most during each experiment. Then, I put the coin under the chest and repeated the same contacts, i.e. onto all the five or six above-mentioned covers or armatures, obtaining the same results. Afterwards, I placed the coin under the stomach, then first on one thigh and then on the other one, and finally under the feet. At the end, I repeated all the five or six contacts with the frog lying on its stomach, with its head and legs completely laid out on a dish or silver plate.
That made already 40 combinations but I experimented with many others, covering the stomach, the flanks etc. with various small shields of foil, applying one or more circular strips of such foil around different parts of the body, as if they were belts, and then inducing communication of any of
these strips with whatever coin or silver plate, once it had been applied to this and that part of the body. Through these experiments I always obtained (if the metal contacts were
made properly, as it is necessary in all these experiments), convulsions of the muscles in the respective parts.
§ 86. In the experiments that have been described until now, one armature has always been made of tin foil and glued to a section of the animal, while the other armature has always been a thick silver plate, which was
not very flexible or not flexible at all, and which was simply put in contact with another part. Now, I have to say that the same results are obtained if we work in the reverse direction, that is to say by applying onto
one section a pliable silver or thin gold foil and onto another section a thick tin or lead
sheet. Or we can also apply, here and there, some thin leaves that fit
in the same way, but some of them are made of tin or lead and others of gold or silver and even of pinchbeck. In conclusion, it is the difference among the metals
that causes everything. We have already discussed the essential topics relative to this phenomenon (§ 72 and this paragraph) and we will have
occasion, in the future, to dedicate more time to it, trying to discover, if it is possible, the reason for it.
§ 87. We have also indicated (§ 60) how,
retaining this diversity of metals, one of the armatures can be omitted and substituted by touching the flap of the only armature,
e.g. tin foil, and at the same time some spots of the bare part with the two ends of the conductor; and with the same end, i.e. with the face of the silver or gold coin
itself, or with the shank of the spoon etc.. In this last way, spasmodic contractions occur just in the contiguous and adjacent muscles and sometimes
only in some fibres. However, an entire limb is often affected, for instance a leg that shakes and
jumps.
§ 88. Now I want to describe the experiments of this kind that I
performed upon other animals and that are quite numerous as well. I carried out experiments above all upon warm-blooded animals, quadrupeds and birds, as I have already mentioned (§ 75 and I
towards the end of Memoir Ia ) and I want to describe my work if I thought it were necessary or very useful.
However since it is easy to apply what we have shown up till now also to such animals, having taken into consideration only the differences in
their structure and animal economy, differences which are not very big as regards the sensitivity of the nerves and the irritability of the muscles, I will not spend too much time talking of such experiments. I will only say, in general, that the results are more or less the same, i.e. the same convulsions and spasms in the muscles, the same movements of the limbs of these animals occur by means of the same
artifice of dissimilar armatures. On the whole, in fact, it is possible to observe the same dependence of
muscles on nerves, since they are shaken under the influence of the nerves themselves We can again see that the muscles
which are either contiguous or near the armatures are the most affected ones and that the only remarkable difference
concerning big animals is that the movements excited are usually less violent if the armatures are very distant one from the other. Sometimes
movement is even lacking completely, above all if the indicated armatures are applied to parts provided with very few nerves or too covered nerves, and to muscles that are not too susceptible of movement, if they are not well applied
or if they are not very dissimilar, when, for instance, one is made of gold or silver, as usual, and the other is made of brass or iron rather than being made of tin or
lea(v).
§ 89. I will therefore not take into consideration the experiments I
performed upon live, intact, small and big animals, since we have already spent enough time discussing in detail the artifices through which we induced what we can call
electric convulsions in various parts of their bodies which were sometimes intact and sometimes deprived of just a few parts of integument, according to necessity. I would like to consider the opposite extreme and show how I
managed to obtain the same convulsions and strong muscular contractions, not in the animals themselves, after they had been beheaded or otherwise killed sometimes soon before the experiment and sometimes a few hours before, but in their cut off limbs, in the small pieces of the limbs themselves and even in fragments and bits of muscle which have smaller proportions than a grain of wheat.
§ 90. The whole artifice, also in this case, comes down to applying two
dissimilar armatures. The best ones are, as usual, tin foil which should stick well to a section of
muscle and a coin or whatever silver plate which should simply touch another part of the muscle itself. In order to create
contact between them, it is sufficient to move the plate or the coin forwards, making it crawl until it touches the adherent foil. It would be better, however, to use refolded wire that should
fulfil the role of conducting arc. If such wire is made of silver or even brass, we could do without coin or plate, since it is sufficient to lean it against a bare part of the limb or muscle
so as to touch that section not only in just one spot but in many, and also to touch the tin foil at the same time. In whatever way the two metals applied to different spots get in contact, shakings,
jerking and convulsions occur in any one or more of the detached limbs, in that part of the cut off limb (it does not matter if it is big or small) which
is placed between the two contacts and in the still communicating muscles.
§ 91. It would take too long, if I wanted to clear up and examine the numerous experiments I
performed upon cut off limbs and pieces of limbs, upon single muscles and pieces of muscle, both of cold-blooded and warm-blooded animals; and it would take too much time even to explain the different events which occurred whenever I changed circumstances and the elements I added. I will only mention, therefore, in
concluding this already too prolix Memoir, two discoveries I made as a result of such experiments I carried out and
which are both equally interesting and useful. The 1st shows that, however irritable they are, not all the muscles but only those which obey the will, the muscles affected by spontaneous
movement, are the ones which contract and have convulsions by means of the artifices we are discussing, i.e.
dissimilar metal armatures. However, the intestines, gizzard and heart, which are all extremely irritable, above all the heart, but deprived of voluntary movements, do not have convulsions at all after they have been affected by such means. On the
other hand, the diaphragm has convulsions, since it evidently also obeys the will.
§ 92. The 2nd discovery, which we have already partially discussed (§ 65 and following paragraphs), shows that sometimes, instead of the usual contractions and muscular movements, the passing flow of electric current which is generated by
dissimilar armatures excites the sensation that is proper to the nerves
situated in the affected section. This happens in the tongue, which, although provoked by means of such artifices, does not have either violent or weak convulsions but it
experiences in its most delicate part, its tip, a sour taste that can be sharper or less sharp and
which is no different from what the tongue tastes when electric
fluid is sprinkled from the end of an artificially electrified conductor.
§ 93. In order to obtain this, it is better, as we have previously indicated, to apply a
thin, well cleaned and polished tin or lead sheet to the tip of the tongue or a bit above and
to push against it with fair strength. Then, we apply a gold or silver coin, a spoon, a spatula or another sheet of such metal, to the middle or
another part of the tongue. As tinfoil, I often employ a sheet of paper called "silver paper",
which is actually paper covered with tin foil. I think that is the best of
all, except that not all the sheets of that paper, which I buy at random, always give the same positive results. Some sheets work so wonderfully that the sour taste I experience, when doing the experiment properly, is so intense that I hardly can bear it; others, when
contact is established, cause the same sensation in me, but it is incomparably weaker. I cannot really think of a reason for this difference, except for the different kind of tin, its alloy with
other metals, having been more or less hammered, etc. (see note in § 72).
§ 94. It is a remarkable thing that this taste keeps on being experienced, and that its intensity grows more and more,
all the time during which the two metals, tin and silver, keep on being applied, one to the
tip and the other to other parts of the tongue and keep on touching each other, so that they create a conducting arc. This proves that the passing of electric
fluid is a continuous, incessant flow from one spot to the other.
§ 95. Another point which deserves the same attention is that,
conducting the experiment inversely, i.e. applying the silver sheet to the tip and
placing the paper coated with silver or rather tin behind the tongue, the taste you experience on
said tip is different. It is not acid but rather alkaline, i.e. acrid, tending to be bitter. However, despite being more pungent and intense when it is tasted, it is impossible to experience it if the circumstances are not the most favourable, i.e. if precisely silver and tin are not opposed and if the latter is not well polished. So, using the tin-plated paper, it is either possible or impossible to experience this taste according to whether its quality is good or not (§ 93). It is much easier to experience the acid taste operating in the first way than to taste the acrid and almost bitter one working in the second way; and the intensity of the taste is greater
when acid than when alkaline. Actually I would not really dare to describe the latter using this adjective.
However we might describe it, the latter taste is in any case very different from the
former and this is enough to prepare the path for new possible discoveries.
§ 96. In conclusion, the electric current that is set in motion just by the application of
metal armatures, affects the nerves in different ways, producing totally different sensations, if it enters or leaves such sense nerves. Does it enter or come out when it produces the acid taste on the tip of the tongue? I prefer to think that it enters, in this case; and when it leaves such tip, it causes the other taste that tends to be alkaline. However, I cannot say that this has been completely proved. Moreover, going further with our conjectures, since the electric
fluid that we moved in various ways produces by itself only different tastes, could it not be the immediate cause of every taste? Could it not be the cause of all the sensations of the other senses? However, let us not abandon ourselves again to these too vague ideas. Let us extend our experiments instead and let us confine ourselves to the consequences and immediate
application of these experiments. This is the line I have taken until now and that I will take
as I go back to this subject in subsequent Memoirs.
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EDITORIAL BOARD NOTES
AND ADDITIONS TAKEN FROM THE MANUSCRIPTS BY A. VOLTA
[1 Here, on page 270, of T. II, of Br. Giorn., the Memoir is interrupted and then it continues on page 35, of T. III, in the same Annals.
On page 287 of T. II of Br. Giorn. The Publisher, under the title: SULL’ELETTRICITÀ ANUMALE ED ALCUNE NUOVE PROPRIETÀ DEL FLUIDO ELETTRICO DEL
SIG. CAV. VOLTA (ON ANIMAL ELECTRICITY AND SOME NEW PROPERTIES OF THE ELECTRIC CURRENT BY
Cav.(*) VOLTA), gives information about new experiments and discoveries made by Volta, relative to the matter, and in particular he announces the discovery which shows how the muscles that are not subject to
voluntary movement are excited by the electricity that is produced by
simple metal contacts, and the other discovery concerning the intense taste that the tongue experiences if two different metal armatures are applied to it.
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Revised by John Coggan, Oxford University
