Let us take our frog again for instance, no longer entire, as in my previous experiments, not only mutilated and dissected as in those of Dr. Galvani, but much more, till it is reduced and torn to small pieces like mince(1). I cut the whole trunk away and retain only the hind legs, slightly
joined together. Having taken the skin away from the legs, I apply and fasten a small piece of tinfoil, a few lines wide and a little more in length, to one part of one of
the leg muscles; to whatever part of the other leg I apply a silver coin or a little silver plate. When the usual communication is established by means of the conducting arc, I observe the usual convulsions and
twitchings in both legs.
After
this, I take that small piece of tinfoil away and put a smaller one in its place. By establishing the usual contacts, there arise weaker convulsions. I gradually reduce this armature, or dress, until I no longer observe any convulsions, or only very weak ones. I then cut away part of the legs, or cut off plenty of flesh all around, and find that this same small armature is enough to make the convulsions reappear. I make the armature smaller still, reducing it to the size of one or two lines square, to the point that the convulsion effect disappears in both the truncated legs. But what
have we here? They reappear again if one of the legs is cut away, that is retaining only the leg, or
rather portion of leg, to which the small piece of metal foil is applied, and placing that portion or stump of a leg by its bare side upon the coin or upon a spoon. Finally, I reduce the metal foil to such smallness that it does not exceed half
a line square and is not even sufficient for the stump in question. Yet, it becomes again sufficient if the stump is dissected and reduced to one single muscle, or portion of muscle no greater than a grain of barley or rice. It is astonishing to see how this tiny bit of flesh contracts, becomes corrugated and palpitates whenever, with a small conducting arc as for example a pin or a coin, the plate on which it rests is touched first and then the tinfoil fragment with which it is dressed above, or conversely first the tinfoil fragment and then the plate; or when the same small bit of flesh is pulled and turned in such a way that the two armatures, viz. the plate and the tinfoil, touch one
another.
These experiments, which among many similar ones I here present by way of example, show that the armatures and especially the one which I call dress, made of metal foil well fitting and adhering to the specimen, must have an extension somehow proportionate to the bulk of the body of the animal, or to the part of it in which one wants to excite
convulsions by means of such an artifice. In other words, the bigger the body or the dissected part on which one operates, the
larger the corresponding metallic armatures must be, and especially one of these, to obtain the effect. Of which behaviour I find clear reason in the explanation already given of the easier and more abundant transfer of the electrical fluid which is obtained with such metallic armatures from one part to the other of the animal body to which they are applied, because
metals are much better conductors than all the animal substances, both fluid and solid. Therefore, the
larger the armature and the more the points of contact, the larger is the amount of electrical fluid which can be transferred.
However, if such points are but few, because the armature is too small or because the bulk of the animal or limb under investigation is large, it happens that there is a very large number of conducting wires inside the animal, by which I mean its fibres, vessels, etc. The quantity of electrical fluid which these wires can all together convey, although being less conducting than
metal, will then be equal or nearly equal to that which can be transferred by the much more conducting but proportionately less extended metallic armature. The electrical fluid will thus continue to flow from one place to the other through the internal parts of the animal, which are true conductors, in the usual or in a slightly modified manner, and will then be unable to exert the impetus which is required to obtain the convulsions. If, keeping the armature
as small and insufficient for the purpose as it is, the number of these animal conductors or internal conducting wires is on the other hand diminished by cutting away some limbs, if there are more, or by cutting off the single limb or portion of limb to which it is applied, the effect, the convulsions, etc. must follow, as indeed we have seen that they do, because in this case the quantity of electrical fluid, which
said internal animal conductors can convey, becomes proportionately less in comparison to that
which the armature can cause to flow externally.
These same experiments would seem to prove another thing, namely that the nerves play little or no role in such muscular
movements, for these take place by simply dressing the muscles, without either insulating or dressing the nerves, and without these determining in
whatsoever manner the current of the electrical fluid according to their direction. How are we to believe that the nerves are involved, given that, with the above explained methods, one single muscle, or rather one single portion of muscle or a small bit of flesh can be put into convulsions and spasms? Yet, several other experiments, either on entire animals, which I have already described and shall further extend in another writing, or
on those with the nerves denuded and other preparations, prove quite openly the very great influence that the nerves can have in these phenomena of animal electricity. I shall here consider only one or two of the most telling ones. Having prepared a frog’s leg with its denuded, hanging crural nerve, I dressed the latter with a small piece of tinfoil and also applied a much larger piece of the same tinfoil fastening it well to the largest muscle. The contractions and convulsions of the whole leg were nevertheless incomparably stronger when touching the foot with one end of the conducting arc and the small piece of tinfoil applied to the nerve with the other end than when touching the much larger piece applied to the muscle. But this is not all: it was not even necessary to touch the foot or another part of the leg with the conducting arc;
it was enough to touch with it the dressed nerve while holding the leg by the instep with my other hand. This was enough, I say, to see the leg
shake and twitch and to feel the strong contractions of the muscles with my very
own hand. On the contrary, nothing happened when touching with the conducting arc only the metallic foil applied to the muscle. To see some effect, some tremor and quivering, it was necessary to touch simultaneously with the same arc some other naked muscle or a plate,
such as a coin, lying on it. In this case the convulsions and spasms were stronger, but less than those excited when touching the dressed nerve. The difference is equally evident and perhaps more so in warm-blooded
animals.
Maybe it is true that, even without the involvement of the nerves, the muscles can contract after the action of animal electricity proper, but their great influence cannot be denied and the contrary is not proved by the above-described experiments, in which we saw
convulsions occur when the armatures are applied to the muscles alone and even to a single small portion of muscle. In the first place, such convulsions, as we have just seen, are neither so strong nor so easily excitable as those which are excited when one of the armatures is applied to the muscles and the other to their nerves. Secondly, is it also true that nerves go into any portion of muscle? Are there not nerves in whatever small portion, even when this is detached? We can then suppose that, although not being absolutely necessary, the nerves can play a greater or lesser role in the motions which the electrical fluid originates in these dissected muscles or muscle
fragments.
And
indeed, if the nerves were not necessary or in any case had
no great influence, why do animals deprived of, or at least not furnished with a true and developed nervous system, not show the same phenomena of animal electricity, that is are not convulsed when the proper armatures are fitted to
various parts of their either entire or dissected bodies? In fact I have tried in vain
with some animals of this class, namely leeches, earthworms and others, and it is quite remarkable that they have not only given me no sign at all of animal electricity proper, but were also little affected by the discharges of artificial electricity, incomparably less than all
other animals furnished with nerves. I have not yet tried if the same is true of all worms or of some kinds only, nor dare I guess the answer. On the contrary, I have made trials upon entire limbs separated from the trunk, upon portions of limbs and upon small portions of muscles belonging to classes of animals not only well provided with nerves but of the most perfect kind, and furthermore upon some species of quadrupeds and birds. In all cases the occurrence has always corresponded, that is I have always obtained the tremors,
convulsions and spasms of greater or lesser strength, even without denuding the nerves, with the armatures simply applied in my way to various muscles or to one part of the same muscle. Let this suffice to give an idea of the extent to which, in less than two months
having been engaged in these experiments, I have carried the research on native animal electricity, proper to living organisms and still subsisting in dissected pieces
while some vitality endures in them; and of the success which these experiments and researches of mine have
achieved. So I will finish this addition here, reserving for other memoirs, as already anticipated, a more exact description and the several applications of so many new experiments, which
are already turning out to be a crowd too large to be digested at one single time.
Revised by John Coggan, Oxford University
