SECTIONII.Application of Galvanism to the organs of hearing and of sight.By applying Galvanism to different parts of the face, a flash of light is excited in the eyes, which is stronger or weaker according to the nature of the parts to which it is directed. These organs, though delicate, are always affected in such a manner that the mechanism of the eye sustains no injury from the metallic arcs when they are made to communicate with only two plates of different metals. I received an account of this phænomenon at Milan, several years ago, from the celebrated Volta, who produced it by applying a conductor of zinc in such a manner, that one end of it touched the bulb of the eye, and the other the tip of the tongue armed with a plate of tin. In administering Galvanism for diseases of the eyes, it is much better to employ the pile. To excite the appearance of a flash of light, it is not necessary that the eyes should be open; it takes place even if they are shut, and covered with a bandage in a darkened apartment. Some of the partisans of Euler, perhaps, may here maintain, that this phænomenon of Galvanism is a deception, and that no light can be really excited in such cases, as the production of light depends on the emanationof rays from a luminous body which penetrate into the interior part of the eye. But without entering into the examination of this question, which is foreign to my principal object, I shall only observe, that long before the theory of Galvanism was known, the celebrated Darwin had found that when the eyes are shut, there are certain internal stimulants which are capable of producing the appearance of light and of colours.In no case is the difference between Galvanism and electricity more apparent than in the application of the former to the sight. Very little benefit had been obtained by means of a metallic point inclosed in a glass tube, which directed the electric charge from a jar to the cornea; and besides, the shock of a Leyden jar applied directly to so delicate an organ as the eye could not but be attended with danger. Galvanism applied to the exterior part of the eye, in the same place where a stream of electricity would have had no influence whatever, has always produced a certain effect on the organ of sight, as is proved by the following experiments.EXPERIMENTI.If you touch with one hand the bottom of the pile, and at the same time apply to the summit different parts of the face moistened with salt water, a flash of light will be excited in the eyes. The same result will be obtained, if instead of touching the bottom of the pile with the hand you touchit with the sole of your foot. No flash of light is observed when the Leyden flask is employed in the same manner.EXPERIMENTII.Having observed the preceding phænomenon in myself, and excited it in others, I was desirous of proving it in regard to several persons at the same time during the course of my public lectures, and for that purpose I made use of the following apparatus. I arranged two metallic plates in a horizontal position, at the distance of nine inches from each other, so that six persons with their hands dipped in salt water could touch the lower plate, and the upper one with the tips of their tongue. A charged Leyden flask placed between the two plates being then discharged, the whole of the persons experienced a violent shock, but perceived no flash of light. It is well known however that, when a similar arc is formed with the interposition of a very strong pile, a flash of light is constantly observed; though the force in the second case is much less than that excited by the explosion of the Leyden flask. The same result will be obtained by bringing the upper plate into contact with the nose.EXPERIMENTIII.As my pupils took much interest in this research, some of them suspected that the light of the apartment might perhapshave effaced that excited by the electricity. I therefore made the apartment entirely dark; and one of them taking a Leyden flask applied it to the point of the nose of another person with whom he was in communication, by laying hold of him with the other hand. By these means a very strong shock was given, but no flash of light was observed. This experiment was repeated, making the person who received the shock of the Leyden flask to remain some time before in the dark, that his eyes might be better enabled to perceive any faint light that might be excited: but the result was still the same. To those who refer Galvanism to the common laws of electricity, it will be difficult to comprehend the cause of the different action exercised by the latter on the organ of sight. But as it is not my intention at present to enter into any discussion on this subject, I shall leave it to philosophers to assign a reason for this phænomenon, and only observe, that the properties above indicated will be sufficient to authorize medical practitioners to prefer, in certain cases, the administration of Galvanism by the pile to that of common electricity.Before I proceed directly to the medical administration of Galvanism to the organ of sight, I think it necessary to distinguish four classes of blind persons whose cases ought to be considered separately.The first belongs to those who from their birth have been deprived of the valuable blessing of sight.The second comprehends those become blind in consequence of some great læsion, or some derangement in the solids or in the fluids which constitute the mechanism of the eye.The third, those who have become blind by some morbid action, though the mechanism of the eye has been little affected, and though no impediment has occurred but in regard to the action of the optic nerve.The fourth class comprehends those who, though not actually deprived of sight, have it much weakened in consequence of disease, or of some other cause.The administration of Galvanism does not hold forth much hope of a cure to persons belonging to the first two classes. I however resolved to attempt some experiments on this subject at Bologna; but though there were a great many blind in that city, I found that they had become so by the malignant influence of the small pox. This observation will, I hope, be of service to the pursuits of the celebrated Dr. Jenner, and of all those who exert themselves to promote the beneficial practice of vaccine inoculation.Being deprived, at Bologna, of any opportunity of trying the effects of Galvanism in cases of persons born blind, I galvanised several who had lost their sight at a very early age. I first applied the Galvanism to the arms of five blindpersons, some of whom had lost their sight thirty, and others forty years and even more. By this method they were familiarised with the idea of its mechanical action, and learned to distinguish it from every other sensation. I then applied Galvanism to the lips, and to the tip of the nose, in a darkened apartment; but in three instances only the patients had a real perception of light, to which they had been so long strangers. I then applied it to cases of amaurosis, and at first had confident expectation of effecting a perfect cure. One of my patients was a woman, whom this disorder had deprived of the sight of one eye, while that of the other was much weakened. After administering the Galvanism different ways, I observed that the eye totally blind began to have a perception of light, and that the sight of the one which was weakened became much stronger. I then took a book, which I held at a considerable distance from her; and removing it gradually further as the Galvanism was administered, I observed, in consequence of this method, that the patient’s sight daily improved. But I must freely confess that the success obtained, though at first flattering, was not of long duration; and that when the Galvanism was discontinued a great deal of the benefit which had been obtained was again lost. On this account, I was discouraged from administering Galvanism any more in such cases. I am however of opinion, that by varying the method of administration it may be attended with some utility. I shall here observe, that having once had occasion to administer common electricity in a similar case of amaurosis, I was never able toexcite the perception of a flash in the eyes of the patient, though the electricity was applied directly to the eye itself.I have had few opportunities of applying Galvanism in diseases of the organs of hearing. Besides, I thought it almost needless to try a method which had been already brought to a state of perfection by some of the most celebrated professors of Germany and Berlin. I admired in particular a very ingenious machine, invented for that purpose by a German philosopher, and lately constructed in England by Mr. John Cuthbertson, an eminent philosophical and mathematical instrument maker, and celebrated for having constructed the large electrical machine of Harlem. The apparatus consists of a metal lever, which by means of certain wheels and machinery rises and falls every minute or second, and at each time of falling forms a communication between certain parts of the patient and the pile. In consequence of this arrangement, the interrupted action of the Galvanism is renewed every time that the communication between the patient and the pile is re-established. Before my departure from London, I made several changes and improvements in the usual construction of this apparatus, in order to give it as much simplicity as possible. The following is the manner in which I caused it to be constructed lately for my own use. One extremity of the lever which forms the communication (PlateIII.fig. 1.), is fixed to the base or negative end of the pile, and the other terminates in a small hammer, so placed as to strike a bell, which by means of abason of water is in communication with certain parts of the patient, while an arc extends from the patient to the summit or positive end of the pile. In consequence of this arrangement, every time that the small hammer strikes the bell the Galvanic action of the pile is repeated. In cases of deafness, I cause the patient to hold in one hand an insulated metallic arc, one end of which is brought into contact with the affected ear, and the other with the positive end of the pile; and to immerse the other hand in a bason of salt water placed above the bell. When this disposition has been made, the wheel-work is turned round, which gives motion to the lever; and every time that the hammer strikes the bell, a communication is formed between the positive and negative ends of the pile: consequently there will then be a circulation of the fluid, and the Galvanism will exercise a direct action on the organ of hearing. The apparatus, constructed in this manner, appears to me to be reduced to great simplicity: and therefore I propose to extend the use of it, by employing it to administer medical Galvanism to other diseased parts of the body.Before I conclude this article, I must suggest a hint respecting the application of Galvanism to diseases of the teeth, founded on information communicated to me on this subject by Mr. Fowler, an eminent dentist of London. When the caries is concealed from the sight, Mr. Fowler employs the following method to discover the affected tooth. He first insulates the patient; and having put into his hand the electricchain, he applies a small piece of wire to thedens sapientiæ, drawing it gradually over its surface: he then applies it to the next tooth, repeating the operation, and proceeds in like manner with the rest till he comes to the diseased tooth, which discovers itself by a violent pain producing an involuntary commotion in the body. It is always remarked, that when this tooth is extracted it exhibits a carious part not before visible. This method, therefore, is of great importance, as it frequently happens in such cases that the dentist, not being able to distinguish the diseased tooth from the rest, is obliged to draw some that are sound before he can discover it.
Application of Galvanism to the organs of hearing and of sight.
By applying Galvanism to different parts of the face, a flash of light is excited in the eyes, which is stronger or weaker according to the nature of the parts to which it is directed. These organs, though delicate, are always affected in such a manner that the mechanism of the eye sustains no injury from the metallic arcs when they are made to communicate with only two plates of different metals. I received an account of this phænomenon at Milan, several years ago, from the celebrated Volta, who produced it by applying a conductor of zinc in such a manner, that one end of it touched the bulb of the eye, and the other the tip of the tongue armed with a plate of tin. In administering Galvanism for diseases of the eyes, it is much better to employ the pile. To excite the appearance of a flash of light, it is not necessary that the eyes should be open; it takes place even if they are shut, and covered with a bandage in a darkened apartment. Some of the partisans of Euler, perhaps, may here maintain, that this phænomenon of Galvanism is a deception, and that no light can be really excited in such cases, as the production of light depends on the emanationof rays from a luminous body which penetrate into the interior part of the eye. But without entering into the examination of this question, which is foreign to my principal object, I shall only observe, that long before the theory of Galvanism was known, the celebrated Darwin had found that when the eyes are shut, there are certain internal stimulants which are capable of producing the appearance of light and of colours.
In no case is the difference between Galvanism and electricity more apparent than in the application of the former to the sight. Very little benefit had been obtained by means of a metallic point inclosed in a glass tube, which directed the electric charge from a jar to the cornea; and besides, the shock of a Leyden jar applied directly to so delicate an organ as the eye could not but be attended with danger. Galvanism applied to the exterior part of the eye, in the same place where a stream of electricity would have had no influence whatever, has always produced a certain effect on the organ of sight, as is proved by the following experiments.
EXPERIMENTI.
If you touch with one hand the bottom of the pile, and at the same time apply to the summit different parts of the face moistened with salt water, a flash of light will be excited in the eyes. The same result will be obtained, if instead of touching the bottom of the pile with the hand you touchit with the sole of your foot. No flash of light is observed when the Leyden flask is employed in the same manner.
EXPERIMENTII.
Having observed the preceding phænomenon in myself, and excited it in others, I was desirous of proving it in regard to several persons at the same time during the course of my public lectures, and for that purpose I made use of the following apparatus. I arranged two metallic plates in a horizontal position, at the distance of nine inches from each other, so that six persons with their hands dipped in salt water could touch the lower plate, and the upper one with the tips of their tongue. A charged Leyden flask placed between the two plates being then discharged, the whole of the persons experienced a violent shock, but perceived no flash of light. It is well known however that, when a similar arc is formed with the interposition of a very strong pile, a flash of light is constantly observed; though the force in the second case is much less than that excited by the explosion of the Leyden flask. The same result will be obtained by bringing the upper plate into contact with the nose.
EXPERIMENTIII.
As my pupils took much interest in this research, some of them suspected that the light of the apartment might perhapshave effaced that excited by the electricity. I therefore made the apartment entirely dark; and one of them taking a Leyden flask applied it to the point of the nose of another person with whom he was in communication, by laying hold of him with the other hand. By these means a very strong shock was given, but no flash of light was observed. This experiment was repeated, making the person who received the shock of the Leyden flask to remain some time before in the dark, that his eyes might be better enabled to perceive any faint light that might be excited: but the result was still the same. To those who refer Galvanism to the common laws of electricity, it will be difficult to comprehend the cause of the different action exercised by the latter on the organ of sight. But as it is not my intention at present to enter into any discussion on this subject, I shall leave it to philosophers to assign a reason for this phænomenon, and only observe, that the properties above indicated will be sufficient to authorize medical practitioners to prefer, in certain cases, the administration of Galvanism by the pile to that of common electricity.
Before I proceed directly to the medical administration of Galvanism to the organ of sight, I think it necessary to distinguish four classes of blind persons whose cases ought to be considered separately.
The first belongs to those who from their birth have been deprived of the valuable blessing of sight.
The second comprehends those become blind in consequence of some great læsion, or some derangement in the solids or in the fluids which constitute the mechanism of the eye.
The third, those who have become blind by some morbid action, though the mechanism of the eye has been little affected, and though no impediment has occurred but in regard to the action of the optic nerve.
The fourth class comprehends those who, though not actually deprived of sight, have it much weakened in consequence of disease, or of some other cause.
The administration of Galvanism does not hold forth much hope of a cure to persons belonging to the first two classes. I however resolved to attempt some experiments on this subject at Bologna; but though there were a great many blind in that city, I found that they had become so by the malignant influence of the small pox. This observation will, I hope, be of service to the pursuits of the celebrated Dr. Jenner, and of all those who exert themselves to promote the beneficial practice of vaccine inoculation.
Being deprived, at Bologna, of any opportunity of trying the effects of Galvanism in cases of persons born blind, I galvanised several who had lost their sight at a very early age. I first applied the Galvanism to the arms of five blindpersons, some of whom had lost their sight thirty, and others forty years and even more. By this method they were familiarised with the idea of its mechanical action, and learned to distinguish it from every other sensation. I then applied Galvanism to the lips, and to the tip of the nose, in a darkened apartment; but in three instances only the patients had a real perception of light, to which they had been so long strangers. I then applied it to cases of amaurosis, and at first had confident expectation of effecting a perfect cure. One of my patients was a woman, whom this disorder had deprived of the sight of one eye, while that of the other was much weakened. After administering the Galvanism different ways, I observed that the eye totally blind began to have a perception of light, and that the sight of the one which was weakened became much stronger. I then took a book, which I held at a considerable distance from her; and removing it gradually further as the Galvanism was administered, I observed, in consequence of this method, that the patient’s sight daily improved. But I must freely confess that the success obtained, though at first flattering, was not of long duration; and that when the Galvanism was discontinued a great deal of the benefit which had been obtained was again lost. On this account, I was discouraged from administering Galvanism any more in such cases. I am however of opinion, that by varying the method of administration it may be attended with some utility. I shall here observe, that having once had occasion to administer common electricity in a similar case of amaurosis, I was never able toexcite the perception of a flash in the eyes of the patient, though the electricity was applied directly to the eye itself.
I have had few opportunities of applying Galvanism in diseases of the organs of hearing. Besides, I thought it almost needless to try a method which had been already brought to a state of perfection by some of the most celebrated professors of Germany and Berlin. I admired in particular a very ingenious machine, invented for that purpose by a German philosopher, and lately constructed in England by Mr. John Cuthbertson, an eminent philosophical and mathematical instrument maker, and celebrated for having constructed the large electrical machine of Harlem. The apparatus consists of a metal lever, which by means of certain wheels and machinery rises and falls every minute or second, and at each time of falling forms a communication between certain parts of the patient and the pile. In consequence of this arrangement, the interrupted action of the Galvanism is renewed every time that the communication between the patient and the pile is re-established. Before my departure from London, I made several changes and improvements in the usual construction of this apparatus, in order to give it as much simplicity as possible. The following is the manner in which I caused it to be constructed lately for my own use. One extremity of the lever which forms the communication (PlateIII.fig. 1.), is fixed to the base or negative end of the pile, and the other terminates in a small hammer, so placed as to strike a bell, which by means of abason of water is in communication with certain parts of the patient, while an arc extends from the patient to the summit or positive end of the pile. In consequence of this arrangement, every time that the small hammer strikes the bell the Galvanic action of the pile is repeated. In cases of deafness, I cause the patient to hold in one hand an insulated metallic arc, one end of which is brought into contact with the affected ear, and the other with the positive end of the pile; and to immerse the other hand in a bason of salt water placed above the bell. When this disposition has been made, the wheel-work is turned round, which gives motion to the lever; and every time that the hammer strikes the bell, a communication is formed between the positive and negative ends of the pile: consequently there will then be a circulation of the fluid, and the Galvanism will exercise a direct action on the organ of hearing. The apparatus, constructed in this manner, appears to me to be reduced to great simplicity: and therefore I propose to extend the use of it, by employing it to administer medical Galvanism to other diseased parts of the body.
Before I conclude this article, I must suggest a hint respecting the application of Galvanism to diseases of the teeth, founded on information communicated to me on this subject by Mr. Fowler, an eminent dentist of London. When the caries is concealed from the sight, Mr. Fowler employs the following method to discover the affected tooth. He first insulates the patient; and having put into his hand the electricchain, he applies a small piece of wire to thedens sapientiæ, drawing it gradually over its surface: he then applies it to the next tooth, repeating the operation, and proceeds in like manner with the rest till he comes to the diseased tooth, which discovers itself by a violent pain producing an involuntary commotion in the body. It is always remarked, that when this tooth is extracted it exhibits a carious part not before visible. This method, therefore, is of great importance, as it frequently happens in such cases that the dentist, not being able to distinguish the diseased tooth from the rest, is obliged to draw some that are sound before he can discover it.