An Account of the Late Improvements in Galvanism. Giovanni Aldini
gradually approached my hand, and strong contractions took place at the point of contact. This experiment proves the existence of a very remarkable kind of attraction, observed not only by myself, but also by those whom I requested to repeat the experiment.
EXPERIMENT III.
The above experiment requires great precision in the preparation, and a considerable degree of vital power in the frog. I have been informed by Professor Fontana, in a letter lately received from him, that this phænomenon depends on very delicate circumstances, which he proposes to explain. He assures me, at the same time, that he has twice seen the nerve attracted, in this manner, by the muscle. Being desirous to render this phænomenon more evident, I formed the arc, by applying one of my hands to the spinal marrow of a warm-blooded animal, while I held a frog in the other, in such a manner that the crural nerves were brought very near to the abdominal muscles. By this arrangement the attraction of the nerves of the frog became very sensible. I performed this experiment for the first time, at Oxford, before Sir Christopher Pegge and Dr. Bancroft, and repeated it in the anatomical theatres of St. Thomas’s and Guy’s hospitals.
EXPERIMENT IV.
I made the same observations on the body of a man as I had before made on the head and trunk of an ox. Having obtained the body of an executed criminal, I formed an arc from the spinal marrow to the muscles, a prepared frog being placed between, and always obtained strong contractions without the aid of the pile, and without the least influence from metals. I obtained the same result, in a certain degree, from the bodies of men who had died a natural death.
EXPERIMENT V.
Let four or more persons hold each other by the hands, moistened by a solution of muriate of soda, so as to form a long animal chain. If the first hold in his hand the muscles of a prepared frog; and if the last, at the other end of the chain, touch the spinal marrow or the crural nerves, contractions will be produced: if the animal chain be broken, the contractions will immediately cease. I performed this experiment, making the animal chain to consist of two persons, before the Galvanic Society at Paris, and in Mr. Wilson’s anatomical theatre, Windmill-street.
PROPOSITION IV.
Muscular contractions can be excited, under certain conditions, without establishing a continued arc from the nerves to the muscles.
EXPERIMENT.
Having obtained the body of an executed criminal, I caused the biceps muscle to be laid bare, and brought near to it the spinal marrow of a prepared frog. By these means contractions were produced in it much stronger than I had ever obtained in warm-blooded animals. I repeated the experiment, being myself insulated, and observed no signs of contraction. The same phænomena were exhibited with the head of an ox, which possessed an extraordinary degree of vitality.
PROPOSITION V.
The effects of Galvanism, in the preceding experiments, do not depend on the action of any stimulant, which occurs in performing the experiments, and ought not to be confounded with the effects of that action.
EXPERIMENT I.
In the experiment of the frog applied to the uncovered biceps muscle of the body of the malefactor, if any other body be made to touch the frog it will remain motionless. This proves that the contractions produced in the frog do not arise from the impulse of the mere contact of the spinal marrow with the muscle of the human animal machine.
EXPERIMENT II.
To remove still further all suspicion of the action of stimulants, in the preceding experiments, I prepared two frogs, and connected the extremities of one with the spinal marrow of the other. I then held in my hand the extremities of one of the frogs, and applied the spinal marrow of the other to the uncovered muscles of the head of an ox, which possessed a great degree of vitality. By these means contractions were produced in both the frogs. It is evident, in this experiment, that the force of the stimulant, if there were any, might act on the second frog, but not on the first.
PROPOSITION VI.
Galvanism is excited in the animal machine without any intermediate body, and merely by the application of the nerves to the muscles.
Several philosophers have endeavoured to obtain this interesting result. Professor Volta, in a letter which he addressed to me, in Brugnatelli’s Journal, observed, “that various parts of animals can excite Galvanism, independently of metals.” Galvani, a short time before his death, proposed two ingenious methods of obtaining this result, and gave me a description of them. This, however, has not been able to destroy the incredulity of some philosophers, who hitherto have confounded Galvanism with metallic electricity, under an idea that all contractions proceed from irritation, produced by the action of metals. For this reason I have, with confidence, announced my method, which enables any one to observe this important result.
EXPERIMENT I.
Having prepared a frog in the usual manner, I hold the spinal marrow in one hand (Plate I. fig. 3.), and with the other form an angle with the leg and foot, in such a manner that the muscles of the leg touch the crural nerves. On this contact strong contractions, forming a real electrico-animal alarum (carillon), which continue longer or shorter according to the degree of vitality, are produced in the extremity left to itself. In this experiment, as well as in the following, it is necessary that the frogs should be strong and full of vitality, and that the muscles should not be overcharged with blood.
EXPERIMENT II.
By observing the directions already given, very strong convulsions will be obtained; but they must not be ascribed to the impulse produced by bringing the nerve into contact with the muscle. If the experiment be repeated, covering the muscle, at the place of contact, with a non-conducting substance, the contractions will entirely cease; but they will be re-produced as soon as the nerve is made to touch the muscular substance. In performing this experiment, in public, I obtained several times more than two hundred successive contractions; but this was never the case when I formed the same contact with the muscle by means of a conducting substance, and even with a plate of metal.
To ensure the success of this interesting experiment, the nerves must be prepared as speedily as possible, by disengaging them from every foreign substance. It will be proper also to apply the nerves not to one but to several points of the muscle, throughout its whole length. It is observed, that the contact of the nerves with the tendinous parts which communicate with the muscles, often serves to increase the muscular contractions. I performed the above experiment before several able professors, among whom were the celebrated Brugnatelli and Carcano, who, with that modesty peculiar to them, made several ingenious observations on the precision which might be given to it. Professor Brugnatelli was apprehensive that, as I had accidentally touched some metals before I performed the experiment, metallic particles might have adhered to my fingers, and thus have served, in some measure, as invisible arming, sufficient of itself to excite muscular contractions. This suspicion, however, I removed, by immersing my hands in water, to detach every foreign substance. He then observed that animal moisture, independently of the circulation of the Galvanic fluid from the nerves to the muscles, might also excite muscular contractions; and he requested that the crural nerves might be washed in common water. This was accordingly done; and the humidity of the nerves being thus externally removed, very strong contractions were still produced, as the professor found, to his full conviction, on repeating the experiment himself several times[1].
[1] It may not be improper here to observe, that my method of exciting muscular contractions, without metals, is very different from that proposed by others. I do not know that convulsions have ever been obtained in cold-blooded animals by means of warm-blooded. From observations I have made, I flatter myself with the hope of being able to obtain contractions without metals, even in the muscles of warm-blooded-animals. But to ensure the certainty of this method would require long practice, and a preparation attended with considerable difficulty. I however propose to attempt