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THE NATURE AND CAUSE OF THE GALVANIC PHENOMENON
By BORIS SIDIS, M. A., PH. D., M. D., BROOKLINE, MASS.
Read before the American
The Journal of Abnormal Psychology, 1910, 5, 69-74.
The Russian physiologist Tarchanov is regarded as the discoverer of the interesting fact that psychic states, sensory, affective, emotional, volitional, and even intellectual processes, such as calculation, solutions of mathematical problems bring about galvanic deflections. As a result of his investigation, which is but a preliminary communication, he conjectures that the deflections may be due to secretory changes going on in the epidermis.
According to Féré, the galvanometric deflections are due to lowering of bodily resistance under the influence of emotional states. The assumptions of skin secretions and the lowering of bodily resistance have been accepted uncritically by almost all investigators of the subject. It is assumed that the galvanic deflections are due to lowering of electrical resistance of the body through the agency of skin secretions produced by psychic states or by psycho-physiological processes. Some investigators also implicate the sympathetic and the central nervous system.
In a study of galvanometric deflections, due to psycho-physiological processes, published in the Psychological Review for September, 1908, and January, 1909,* we demonstrated by a series of experiments that the galvanic phenomenon is not due to a change of resistance of the body, but to an electromotive force generated in the organism. We come to the following conclusion: "Active psycho-physiological processes, sensory, and emotional processes, with the exception of purely ideational ones, initiated in a living organism bring about electromotive forces with consequent galvanometric deflections." In a new series of experiments performed on animals such as frogs, rabbits, and cats we further confirm the nature of the galvanic phenomenon and demonstrate its causation. This last study is to appear in the Psychological Review, March, 1910. I can give here but a bare outline of it.
All investigators of the subject use cells in their circuit. In our experiments cells were excluded from the circuit. We worked with non-polarizable subcutaneous electrodes. The galvanometer was of D'Arsonval type, sensitivity, 225 megohms. The deflections of the ray were in centimeters and millimeters. Later on a special mechanism was devised for photographing the deflections. Let me give an example of a couple of experiments: Hypodermic electrodes inserted in forelegs of rabbit.
|Zero reading, when circuit open........................24cms.
Zero reading, when circuit closed......................24cms.
Stimulus, prick....................................rose to 24cms.
Galvanometer, returned to................................24cms.
Fresh rabbit hypodermic electrodes inside of thigh:
Zero reading, circuit open..................................24cms.
Galvanometric reading, circuit closed................24cms.
Stimulus, snap on nose, galvanometric deflection rose to 20.50 returned to 24 centimeters
Anæsthetics such as chloroform and ether abolished the galvanic phenomenon which reappeared when the effect of the anæsthetic passed off. It was also observed that violent peristalsis, struggles, twitchings, and convulsions produced under the influence of various drugs, such as aloin, oleum ricini, oleum tiglii, apomorphine, strychnine, and others, in short all forms of motor activity, produced marked galvanometric deflections.
In the first part of our work on animals we were led by our experiments to the following conclusions:
(1) Every sensory stimulation of an affective or emotional value is accompanied by galvanic deflection.
(2) Motor reactions intensify the galvanic phenomenon, giving rise to more extensive deflections.
(3) Motor activity by itself is sufficient to give rise to large galvanometric deflections.
(4) The subcutaneous electrodes excluding the epidermis prove that the galvanic perturbations produced by stimulations are not due to skin effects.
On opening and closing the circuit the galvanometric zero reading remains unchanged, that is, there is no current flowing in the circuit. If now with circuit closed and galvanometer at zero reading, we prick, pinch, burn, or stimulate the animal in various ways, we get galvanometric deflections. It is clear that we deal here not with a change of resistance, whether of skin or of body, but with generation of an electromotive force. Our experiments therefore prove conclusively that the galvanic phenomenon is not due to changes of resistance, but to electromotive forces induced in the organism by the psychophysiological processes under the influence of external stimulations.
An examination of the results under anæsthesia showed large galvanometric perturbations when the anæsthetic was administered, and again when the animal was passing from under the influence of the drug. Stimulations produced marked deflections during the period preceding and following the state of deep narcosis. We could not help, however, noticing that movements and struggles on the part of the animal were uniformly accompanied by large galvanometric deflections. When the motor activity diminished the observed galvanometric deflections decreased correspondingly, and when the animal was completely motionless the galvanic perturbations entirely disappeared. The same relation was observed in the case of various drugs inducing peristalsis. Peristalsis accompanied by motor activity, by struggles, twitchings, shiverings, convulsions, and generally by muscular contractions, produced galvanometric deflections proportionate to the extent of muscular activity. Where all motor activity was absent, although the action of the drug continued, no galvanometric changes could be detected. Thus in the case of peristalsis, accompanied by large contractions of the intestinal tract and by general condition of straining of abdominal muscles there were large deflections. During the intermediate period of peristalsis when the animal was quiet no deflections were present. This also holds true even of such cathartic drugs as aloin and croton oil. The effect of apomorphine is especially interesting from this standpoint. The injection of apomorphine into the rabbit does not produce vomiting, but causes continuous shivering and twitchings of almost all the muscles. The result is a corresponding ceaseless fluctuation of the mirror-galvanometer. Not less instructive is the injection of strychnine, which gives rise to twitchings and convulsions with corresponding deflections of the mirror galvanometer.
The same relation holdstrue, even in the case of the galvanometric deflections due to various stimulations. Where the stimulation was accompanied with motor reaction there the deflection was manifest; where such reaction was absent the galvanic deflection did not appear. All these facts point to the conclusion that the concomitant motor activity plays an important and possibly a predominant role in the causation of the galvanic phenomenon.
If such relation between motor activity and the galvanic phenomenon exists, it should be demonstrated, after all other possible factors are rigidly excluded, by some crucial experiments.
The first crucial experiment that naturally suggests itself is the restriction of the muscular activity of the animal and the observation of galvanic deflections when the animal is stimulated by pinches pricks, snaps. and various other painful agencies. If muscular contractions are concerned in the causation of the galvanic phenomenon, we should find that with their diminution and total suppression the galvanic phenomenon should be correspondingly' decreased and even totally abolished. With this end in view we performed the following experiments:
The hind legs of a rabbit were firmly bound, so that they could not move. With the platinum electrode inserted well into the muscles of the motionless thighs the circuit was closed. Under such conditions no stimulations however painful could call forth galvanometric deflections. In other words, with the suppression of muscular action the galvanic reaction disappears.
With the platinum electrodes in the same position one of the legs was left free to move. When the rabbit was now stimulated, the free leg, of course, contracted, and the galvanic deflections were evident in response to each stimulation. In other words, with the reinstatement of muscular action the galvanic phenomenon once more reappeared. The experiment is crucial, inasmuch as it excludes all other possible factors, such as secretion, whether of skin or of other glands; it excludes circulation, whether of lymphatics or of blood vessels, and rules out the action of the sympathetic and of the central nervous system. For if any of these physiological processes give rise to the galvanic phenomenon the latter should persist in our experiments, since all these processes are not arrested with the restriction of the movements of the leg.
In our previous experiments we have excluded circulation as the cause of the galvanic phenomenon. This was accomplished by means of Esmarch bandages. In our present experiments with animals we excluded circulation by ligations of the arteries supplying the limb. Under such conditions the galvanic phenomenon still persisted.
The skin effects have practically been excluded by the whole course of our experiments, inasmuch as we worked exclusively with hypodermic electrodes, and were still obtaining the galvanic phenomenon.
The skin effects can also be ruled out by the following experiment: The animal is securely immobilized and the electrodes are inserted into the skin. The galvanic phenomenon is absent with the immobilization of the limbs.
If, on the other hand, the skin is stripped clean from the hind legs of a frog (the skin comes off smoothly and easily), and the electrodes are inserted into the striped muscles, the galvanic phenomenon persists and is quite marked.
We can now account for the significant fact that struggles, twitchings, and convulsions are followed by large galvanometric deflections. All our experiments tend to prove that the galvanic phenomenon is essentially a muscular phenomenon. In other words, the observed galvanometric deflections under the influence of affective states are due to electromotive forces liberated by muscular activity brought about by sensory, emotional, and affective processes.
That the galvanic reaction is entirely muscular in origin can he still further demonstrated by the following experiments:
The motor nerves of the muscles of the legs of a frog were cut so that the legs were paralyzed. The platinumelectrodes were inserted into the paralyzed muscles. Under such conditions the galvanic phenomenon was completely absent. No stimulations, however intense and painful, could call forth the vanished galvanic reflex.
The experiment of section of the motor nerves of the legs is a crucial one, inasmuch as the galvanic phenomenon disappears on the paralysis of muscular activity, although all other conditions—skin secretions, circulation, and sensation—remain unchanged. Moreover, the galvanic phenomenon can be reinstated, even under conditions of paralysis of motility by bringing about passive contractions of the muscles of the leg.
Another crucial experiment is that of injection of curare. It is a well-known fact that curare paralyzes only striped or voluntary muscles, all other functions remaining unaffected. Now when the frog or the rabbit is injected with curare and kept alive by artificial respiration, the galvanic phenomenon disappears. In other words, the paralysis of muscular activity causes the disappearance of the galvanic phenomenon.
Thus all our experiments prove incontestably that the galvanic phenomenon is due to an electromotive force which is muscular in origin.
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