THE CAUSATION OF THE GALVANIC PHENOMENON
The problem of the causation of the galvanic phenomenon is highly complex. The physiological processes concerned in phenomenon may be secretory, coming from skin or other glandular organs; may be circulatory, due to the blood vessels or lymphatics; may be due to intestinal changes, such as peristalsis; may be nervous, due to the action of the central or sympathetic nervous. system, or may be due to tissue-metabolism and activities taking place in the organism, or all of them may participate in the production of the galvanometric deflections brought about by various sensory stimulations. It is by no means easy to disentangle such an intricate mesh of factors. At one stage in our work the experiments seemed to indicate as if peristalsis, with its complex metabolic processes, were concerned in the phenomenon. Thus when the hypodermic platinum electrodes were inserted into the legs or the chest, the initial maximum deflection was about 3 centimeters, the initial deflection when electrodes were inserted in the abdomen was far larger, often amounting to more than 50 centimeters, the ray occasionally getting off the scale. Moreover, constant rapid galvanometric oscillations were present, oscillations not observed when electrodes were inserted in any other place than abdomen. To give a few of our experiments:
Experiment I.―Live rabbit.
Experiment II.―Live rabbit.
Experiment III.―Live rabbit (new).
Galvanometer keeps on oscillating between 24 and 25 with an occasional large deflection of more than 50 centimeters ascribed to a possible 'rapid transit' of food in the intestinal tract.
An autopsy, however, of the rabbit showed that the intestinal tract was injured in many places by the electrodes giving rise a number of points of hemorrhage. The results therefore were pure artefacts produced by demarcation-currents or currents of injury having little or nothing to do with the galvanic phenomenon.
Experiment IV.―Live rabbit.
Platinum electrodes in abdomen, electrodes put so that they would produce no scratches, perforations and points of hemorrhage. Under such conditions the galvanometric deflection when circuit is closed: 26 - 24.50 - 24 cm. One fact, however, was of great interest from our standpoint and that was the relatively larger extent of the deflection produced by various stimulations and motor activities of the rabbit, the deflections varying from 4 to 10 and even to 20 centimeters.
We then decided to open the abdomen and find whether there could be directly observed any relation between peristalsis and galvanometric deflections.
Experiment V.―Rabbit given three grms. of urethane. Abdomen opened; intestine exposed; rabbit put into bath of 0.8 per cent. sodium chloride solution.
Experiment VI.―After 24 hours dead rabbit in same bath. The oscillation is of the same magnitude from 1-2 centimeters. Platinum electrodes taken out of the rabbit and put in the salt solution alone; the galvanometric deflections were observed to be of the same magnitude, of 2 cm. It was evident that the deflections and oscillations were due solely to the chemical processes and electrical currents generated by them. To clinch the proof the rabbit was taken out of bath and washed with clean water and then electrodes inserted into the abdominal cavity. No further changes were observed. The oscillations then were artefacts and could certainly not be ascribed to the action of peristalsis. We were then on the wrong track. Still the fact remained that with the electrodes in the abdomen and with all the precautions against injuries and scratches which the autopsies of the rabbits showed to be absent there were undoubtedly relatively far larger deflections than when the electrodes were placed in any other part of the body.
The large abdominal galvanometric deflections which sometimes occur so sporadically gave us good cause to think that we may be here on the track of some of the important factors concerned in the causation of the galvanic phenomenon and that could only be accomplished by a more perfect method of recording the results of our experimentation. What we needed was a record of all the galvanometric deflections that had taken place,―to get, so to say, a continued history of all the changes that had taken place during a certain period. In short, what is requisite is a graphic method and the best graphic method is to get a photographic record which has the advantage of being trustworthy, automatic and continuous. Not only should the photographic records give good continuous curves, but the curves should be for long periods. The apparatus should give us a continuous photographic record at least for a period of two hours. At the same time there should be a chronograph marking time and a marker indicating any important change or time of stimulation. The following is a description of apparatus used:
The apparatus consists of a Ludwig kymograph K to which is attached a system of two drums D, Dl by means of two pulleys P, Pl and belt H. Around the belt there is wound a belt of paper to which a length of six feet of photographic paper may be attached. The galvanometer G is placed on a solid table built to the wall, so that no vibrations should affect it. The source of light is L, a Nernst lamp, which is well covered by a box having a very small narrow vertical slit in it. The pencil of rays coming from the narrow vertical slit is reflected in mirror of the galvanometer which is placed in the focal distance from a screen S with a horizontal slit which reduces the reflected rays coming from the galvanometer to a point of light. This ray of light passing through the horizontal slit of the screen falls on the sensitive paper H attached to the belt of paper around the two drums.
For recording the time there is a time-marking device C1C2C3S1 which consists of an ordinary alarm clock with a prolonged second hand dipping every minute into a cup of mercury thus closing a current coming from three cells. This current is transmitted to a telegraph-sounder S1 which marks the on the sensitive paper. By means of a key K1 the same current is shunted and used to indicate on the revolving sensitive paper the time of stimulation or any other important event taking place during the experiment.
The apparatus fulfilled all the conditions outlined above,―it gave a long and continuous record of the history of the galvanic happenings. As the photographic record was registered automatically on the sensitive paper we could turn our attention to the rabbit and watch closely any disturbances in the animal. Since the light reflex moving on the brass slit could be easily noticed in the darkened room even from a distance of several meters, it was an easy matter to watch the disturbances taking place in the animal as well as any galvanometric perturbations occurring simultaneously. The time of the disturbances was automatically recorded by the marker on the sensitive paper. The marking of the stimulations and of the changes in the animal placed each event, as it occurred, in its proper position with regard to the galvanic curve. This enabled us to correlate at a glance the disturbances in the animal with the corresponding galvanometric deflections. Armed with this technique we returned with a renewed vigor to the attack of the problem of the causation of the galvanic reaction due to psycho-physiological processes.
In order to come somewhat more closely to the main factor concerned in the production of the galvanic phenomenon it was thought that it might be well to approach the problem by subjecting to test sensitivity itself, especially the affective or the algedonic tone of it which has been demonstrated to be somehow related to the galvanic phenomenon under investigation. In modifying the sensitivity it was hoped that we might possibly be enabled to observe the simultaneous variations of some other factor more closely connected with the various changes of the galvanic reaction.
If again peristalsis is somehow concerned in the causation of the galvanic phenomenon, the modifications of peristalsis should also affect the galvanometric perturbations or possibly that factor which is directly concerned in the causation of the galvanometric deflections.
The modifications of sensitivity, gradual decrease and even total annihilation of sensitivity and then again its gradual increase, are brought about by various anæsthetics, especially, ether and chloroform, while the modifications of peristalsis can be brought about by various purgatives such as magnesium sulphate, oleum ricini, oleum tiglii, etc.
The foregoing (Curves XI, XII) are the photographic records taken of the rabbit under the influence of chloroform and ether with or without stimulation.
An examination of the photographic records under anæsthesia, discloses the facts of large galvanometric perturbations when the anæsthetic is administered and again when the animal is passing from under the influence of the drug. Stimulations produce more or less marked deflections during the period preceding and following the state of deep narcosis. We notice one important circumstance and that is the fact, that such marked galvanometric deflections are uniformly accompanied by movements and struggles on the part of the animal. When the motor activity diminishes the galvanometric deflections decrease correspondingly and when the animal is quiet the galvanic perturbations completely disappear. The same relation is also observed in the case of the various drugs inducing peristalsis. Peristalsis accompanied by motor activity such as struggles, twitchings, shiverings, convulsions and generally by muscular contractions produce galvanometric deflections which seem to be proportionate to the extent of the observed muscular activity. Where motor activity is absent, although the action of the drug continues with its consequent peristalsis no galvanometric changes can be detected. Thus in the case of defecation which is accompanied by large contractions of the intestinal tract and general condition of straining there are large deflections, while during the intermediate periods of peristalsis, when the animal is quiet no deflections are present. This also holds true even of such cathartic drugs as aloin and croton oil. The curve 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 galvanometric deflections. No less instructive is the injection of strychnine which gives rise to twitchings and convulsions with corresponding deflections of the mirror-galvanometer well brought out in the following photographic record:
The same relation holds true even in the case of the galvanometric deflections due to various stimulations. Where the stimulation is accompanied with motor reaction there the deflection is manifest, where such reaction is absent the galvanic deflection does not appear. All those 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.
This agrees with the work of Sidis and Kalmus who have observed in their experiments that coughing, laughing, sitting, rising, bending arms and muscular activity in general give rise to marked galvanometric deflections. "From these experiments," they say, "it seems that muscular activity of those parts of the body actually forming the circuit bring about galvanometric deflections, while activity of the more remote parts are ineffective."1 We certainly must take issue with Jung and Peterson in their claim that the galvanometric deflection due to coughing is ‘psychic, that is, emotional.' The galvanometric deflection in coughing as well as in like physiological activities is entirely of muscular origin which mayor may not be accompanied by an emotion.
That the obtained galvanometric deflection during stimulation and consequent contraction of muscles in the circuit is not the effect of movement of the electrodes inserted in the tissues of the animals can be demonstrated by the experiment of moving the electrodes to which are attached insulated rubber bands. Such movements of electrodes, but with no muscular contraction, give no galvanometric deflections. This is to be seen from the following photographic records:
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 to restrict the muscular activity of the animal and see what happens to the galvanic deflections, when the animal is stimulated by pinches, pricks, sharp snaps and various other painful agencies. If muscular contraction is 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 experiment:
The hind legs of the rabbit were firmly bound so that they could not move. The circuit was closed with the platinum electrodes inserted well into the muscles of the motionless thighs. 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. This is clearly demonstrated by the Curve XVIa.
With the platinum electrodes in the same position one of the legs was let free to move. When the rabbit was now stimulated the 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 as demonstrated by the Curve XVII.
This experiment is crucial, inasmuch as it also 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 excludes also the action of the sympathetic and of the central nervous system. For if the galvanic phenomenon is due to any, or all of those physiological processes, the galvanic phenomenon should be present under the influence of stimulation, since those physiological processes are not arrested with the restriction of the movements of the limb.
Of course, the skin-effects have practically been excluded by the whole course of our experiments, inasmuch as we worked exclusively with subcutaneous electrodes and still obtaining the galvanic deflections in response to various stimulations.
That the skin effects or secretion-currents2 have nothing to do with the galvanic phenomenon can be further shown by the experiment that when the electrodes are inserted into the skin only, the deflections are made to disappear with the immobilization of the limbs as shown by the Curve XVIII.
In experimenting on the cat similar results are obtained. When the cat is immobilized no sensory stimulations, such as pricking or pinching, can possibly produce any galvanometric deflection. When however the movements of the animal are made somewhat freer so as to make possible muscular contractions the galvanic perturbations under the influence of sensory stimulations become manifest.
Experiments performed on the frog exclude skin resistance and glandular skin secretion as possible factors in the causation of the galvanic phenomenon.
If the frog is put on the animal board, the platinum electrodes put into the muscles and the animal well bound and stretched out on the board so as to arrest muscular activity, the galvanic deflections due to stimulations diminish with the restriction of muscular activity and disappear with the complete arrest of muscular reaction to external stimulation. The galvanic phenomenon remains absent when the platinum electrodes are wound around the freely secreting skin of the frog, or on the inside of the skin layer, or one electrode is put on the outside and one on the inside of the skin. In all such cases, provided the muscular activity of the frog is arrested, the galvanic phenomenon is absent.
If the frog is curarized, thus abolishing the action of the muscles, but not affecting sensitivity, the platinum electrodes inserted into the muscles call forth no galvanic deflection. If the electrodes are now put into the skin or on the inside and outside of the skin layers, no sensory stimulation, however violent, can call forth the galvanic phenomenon.
That the glandular secretion has nothing whatever to do with the galvanic phenomenon can be further demonstrated by the following experiment:
The skin of the frog is easily removed from both legs leaving exposed the muscles of the legs into which the platinum electrodes are inserted. When the galvanometer is at zero and remains stationary, the animal, with legs free, is stimulated by sharp pricks or pinches, with each stimulation and concomitant muscular reaction there is a marked galvanometric deflection amounting, in some cases, to more than 20 millimeters. Under such conditions the following characteristic curve is obtained (Curve XVIIIb):
The brain, the spinal cord, the sympathetic nervous system as well as the action of other internal organs, such as liver and spleen, have likewise been directly eliminated by us. We plunged our platinum hypodermic electrodes into the tissues of those various organs and found that when muscular contractions were not present the galvanic phenomenon was invariably absent.
Similarly circulation can be directly excluded. Already Sidis and Kalmus excluded circulation as the cause of the galvanic phenomenon by the use of Esmarch bandages. In the case of animals, such as the rabbit or the frog, it is possible to exclude circulation by ligation of the arteries supplying the limbs. Under such conditions the galvanic phenomenon still persists showing that blood circulation is not among the causes of the galvanic phenomenon. The following (Curve XIX) is a photographic record of such experiments:
That the galvanic reaction is entirely muscular can be still further demonstrated by the following experiment:
The sciatic nerves were cut and platinum electrodes inserted into the muscles of the legs. Under such conditions the galvanic phenomenon was absent. No stimulations, however intense and painful given in different parts of the body, could call forth the galvanic phenomenon as shown by the following photographic record: (Curve XX)
Similar experiments were also performed on frogs and with the same results. With the platinum electrodes in the gastrocnemius of each leg the galvanic phenomenon invariably disappeared when the sciatic nerves were cut. The fol1owing curve (Curve XXI) is a photographic record of the experiment:
The experiment of section of the motor nerves of the legs is also a crucial one, inasmuch as the galvanic phenomenon disappears on the paralysis of muscular activity, although all other conditions, skin secretions, circulation and sensory nerve processes remain unchanged. Moreover, it may be added that the galvanic deflections can be reinstated even under condition of paralysis of motility by passive contraction of the muscle of the leg, as demonstrated by the following photographic record: (Curve XXII).
We can now explain the large galvanometric perturbation obtained in the case when the hypodermic electrodes are inserted into the abdominal wall. The animal in all of our experiments was tied on a board so that the extremities were naturally more limited in their movements than the abdomen, which remained free to react to painful stimulations.
We are also in a position to account for the significant fact, present in all of our experiments, namely, that struggles, twitchings and convulsions are followed by large galvanometric deflections. For our work proves conclusively that the galvanic reflex is a muscular phenomenon. The galvanometric deflections are due to electromotive forces liberated by muscular activity under the influence of affective and emotional states.
Another crucial experiment is that of injection of curare. It is well known that curare only affects the striped or voluntary muscles leaving all other functions unimpaired. Now when the frog or the rabbit is injected with a dose 2 c.c. of 1 per cent solution of curare and kept alive by artificial respiration the galvanic phenomenon completely disappears. The paralysis of muscular activity causes this disappearance of the galvanic phenomenon. The following photographic record shows the results of the experiments under the influence of curare: Curve XXIII.
Marked rhythmical deflections are obtained from muscular contraction of heart as shown by Curve XXIV.
CURVE XXIV. Platinum electrodes wound around heart of rabbit. Rabbit injected with 4 C.c. of 1 per cent. solution of physostigmine. Deflections are synchronously with the contractions of the cardiac muscle. No cells; no shunt.
We can now understand the reason of the apparent paradox puzzling to Jung and Peterson when they say "there are features presented which are as yet quite inexplicable, as for instance the gradual diminution of the current in long experiments to almost complete extinction, when our ordinary experience teaches that resistance should be much reduced and the passing current larger and stronger." The reason why Jung and Peterson find the fact of ‘the gradual diminution of the current’ so 'inexplicable' is because they have totally misconceived the nature and cause of the galvanic phenomenon. In the first place, we do not deal here at all with resistance, but with an electromotive force. In the second place, the electromotive force generated is muscular in origin. This makes 'the gradual diminution of the current in long experiments to almost complete extinction' an absolute necessity. For it is clear that an electromotive force cannot possibly become stronger and larger 'with continuous use.' That would be against all the laws of physics, With continuous use the muscles become exhausted and with the repetition of the same stimulus a lesser impression is made on the sensory nervous system calling forth a smaller and smaller muscular reaction with its accompanied diminution of electromotive force and consequent decrease of galvanometric deflection. This is demonstrated by Curves XXV, XXVI, XXVII.
We may say then that all our experiments prove incontestably that the galvanic phenomenon is due to an electromotive force which is muscular in origin.
In conclusion we may make the following summary of our results:
We are glad to thank Professor Franz Pfaff, of the Pharmacological Department of Harvard Medical School, for the many opportunities and courtesies shown us in the carrying out of this experimental work.