An Account of the Late Improvements in Galvanism. Giovanni Aldini
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AN ACCOUNT
OF THE LATE
IMPROVEMENTS IN GALVANISM.
A just tribute of applause has been bestowed on the celebrated Professor Volta for his late discovery; and I have no desire to deprive him of any part of that honour to which he is so justly entitled; but I am far from entertaining an idea that we ought, on this account, to neglect the first labours of Galvani. Though these two philosophers pursued different routes, they concurred to throw considerable light on the same points of science; and the question now is, to determine which of them deduced the most just consequences from the facts he observed; and then to ascertain whether the facts established by Galvani lead to the theory of Volta, or whether those discovered by Volta are connected with the theory of Galvani. For my part, I am of opinion that these two theories may serve in an eminent degree to illustrate each other.
Last year Professor Volta announced to the public the action of the metallic pile. I here propose to exhibit, according to the principles of Professor Galvani, the action of the animal pile.
Such is the plan I have conceived in order to reconcile the systems of these two illustrious philosophers: it forms the object of the present work, which is divided into three parts. In the first I shall exhibit the action of Galvanism independently of metals, and explain some of its general properties. The second will contain experiments on the power of Galvanism to excite the vital forces. In the third I shall propose some useful applications of it to medicine, and explain the principles on which the new medical administration of Galvanism is founded. To render the work as methodical as possible, I have endeavoured to arrange the experiments in such a manner that they may serve as proofs to a series of general propositions, which, it is hoped, will be of use to physiology and to the doctrine of the animal economy.
PART THE FIRST.
OF THE NATURE AND GENERAL PROPERTIES OF GALVANISM.
PROPOSITION I.
Muscular contractions are excited by the development of a fluid in the animal machine, which is conducted from the nerves to the muscles without the concurrence or action of metals.
EXPERIMENT I.
Having provided the head of an ox, recently killed, I thrust a finger of one of my hands, moistened with salt water, into one of the ears (Plate I. fig. 1.), at the same time that I held a prepared frog in the other hand, in such a manner that its spinal marrow touched the upper part of the tongue. When this arrangement was made, strong convulsions were observed in the frog; but on separating the arc all the contractions ceased.
This experiment will succeed still better if the arc be conveyed from the tongue of the ox to the spinal marrow of the frog. This method was found to be exceedingly convenient for trying the effect of Galvanism on several calves.
EXPERIMENT II.
Having provided the trunk of a calf, I conveyed the arc from the muscles of the abdomen to the spinal marrow of a frog, prepared and arranged in the usual manner. The frog seemed much affected, and the contractions were exceedingly violent when the arc was composed of a chain of different persons, united together by the hands moistened with salt water.
EXPERIMENT III.
I connected, by means of one chain of moisture, the heads of two or three calves, and observed that by this combination the force of the Galvanism was exerted with more energy: a frog, which was not affected by touching one head, experienced violent contractions when applied to a series of several heads connected together.
EXPERIMENT IV.
I think it proper here to mention a very curious observation which I made lately at Paris, in company with professor Huzzard, and in the presence of the Commissioners of the National Institute. On applying the spinal marrow of a prepared frog to the cervical muscles of a horse’s head, separated from the body, no muscular convulsions took place; but if, at the same time, another person touched with his hand, moistened by a solution of muriate of soda, the spinal marrow of the horse, convulsions were always produced in the frog, though there was no communication between the persons, except that formed by a floor on which they stood.
PROPOSITION II.
The Galvanism excited, in the preceding experiments, is not owing to the communication nor to the transfusion of the general electricity, but to an electricity peculiar to animals, which acts a very distinguished part in the animal economy.
EXPERIMENT I.
Having placed the trunk of a calf (Plate I. fig. 2.) on an insulated table, I made a longitudinal incision in the breast, in order to obtain a long series of muscles uncovered. I then arranged two insulated persons in such a manner that the one with a finger, moistened by salt water, touched the spinal marrow of the calf, while the other applied the spinal marrow of a frog to the muscles of the trunk. Every time this arc was formed, muscular contractions were produced in the frog. When the two persons let go each other’s hands, the contractions ceased. I repeated this experiment, with the same success, on the insulated head of an ox, conveying the arc from the spinal marrow of the frog to the tongue. Frogs were as violently affected when the experiment was made with the insulated trunks of different kinds of birds.
This experiment, in my opinion, affords a decisive proof that the Galvanic fluid is peculiar to the animal machine, independently of the influence of metals, or of any other foreign cause. In these experiments, indeed, we have some animal machines, so combined that the result is strong contractions in the frog. All the bodies were insulated; and, therefore, it cannot be supposed that the contractions were occasioned by the direct influence of that general principle, which pervades every body in nature. Hence it is evident, whether it be ascribed to the action of the animal chain, formed by the arms of the persons, or to the animal pile, formed by the trunk of the calf, that we shall still be obliged to acknowledge the action of a principle which belongs to the organization of the animal machine, without having any dependence on metals.
To prove in the animal body the existence of a principle which philosophers can by certain means excite and direct at pleasure in their experiments, is a matter of the greatest importance; though the manner in which it is put in action by nature, however wonderful, is unknown to us. Here then we have developed a very energetic fluid, capable of transmission, and deriving its origin from the action of the animal forces; since the parts of bodies separated from the common reservoir of general electricity have still of themselves the faculty of reproducing it, and of causing it to circulate in a manner proper for exciting muscular contractions.
PROPOSITION III.
Galvanism develops itself in a powerful manner, independently of metals, by means of the human animal machine.
EXPERIMENT I.
If you hold in your hand, moistened with salt water, the muscles of a prepared frog, and apply the crural nerves to the tip of your tongue, you will immediately see violent contractions produced in the frog. All suspicion of any stimulant exerting an action in this case, may be removed by repeating the experiment with the frog held in the dry hand: the muscular contractions will then cease, unless the action of Galvanism in the frog, or in the animal machine, be uncommonly powerful; in which case contractions may be produced without establishing an arc from the nerves to the muscles.
EXPERIMENT II.
I held the muscles of a prepared frog in one of my hands, moistened by salt water, and brought a finger of the other hand, well moistened, near to the crural nerves. When the frog possessed a great deal of vitality