Popular Science Monthly/Volume 18/November 1880/Hypnotism
By G. J. ROMANES.
CONSIDERING the length of time that so-called "animal magnetism," "mesmerism," or "electro-biology," has been before the world, it is a matter of surprise that so inviting a field of physiological inquiry should have been so long allowed to lie fallow. A few scientific men in France and Germany have indeed, from time to time, made a few observations on what Preyer has called the "Kataplectic state" as artificially induced in human beings and sundry species of animals; but anything resembling a systematic investigation of the remarkable facts of mesmerism has not hitherto been attempted by any physiologist in our generation. The scientific world will therefore give a more than usually hearty welcome to a treatise which has just been published upon the subject by a man so eminent as Heidenhain. The research of which this treatise is the outcome is in every way worthy of its distinguished author; for it serves not only to present a considerable and systematic body of carefully observed facts, but also to lead the way for an indefinite amount of further inquiry along the lines that it has opened up.
Heidenhain conducted his investigations on medical men and students as his subjects, one of them being his brother. He found that, in the first or least profound stage of hypnotism, the patient, on being awakened, can remember all that happened during the state of mesmeric sleep; on awakening from the second or more profound stage, the patient can only partially recollect what has happened; while in the third, or most profound stage, all power of subsequent recollection is lost. But, during even the most profound stage, the power of sensory perception remains. The condition of the patient is then the same, so far as the reception of sensory impressions is concerned, as that of a man whose attention is absorbed or distracted; he sees sights, hears sounds, etc., without knowing that he sees or hears them, and he can not afterward recollect the impressions that were made. But the less profound stages of hypnotism are paralleled by those less profound conditions of reverie in which a passing sight or sound, although not noticed at the time, may be subsequently recalled by an effort of the will. Further on in his treatise Heidenhain tells us that, even when all memory of what has passed during the hypnotic state is absent on awakening, it may be aroused by giving the patient a clew, just as in the case of a forgotten dream. This clew may consist only of a single word in a sentence. Thus, for instance, if a line of poetry is read to a patient during his sleep, the whole line may sometimes be recalled to his memory, when awake, by repeating a single word of the line. Again, we know from daily experience that the most complicated neuro-muscular actions—such as those required for piano-playing—become by frequent repetition "mechanical," or performed without consciousness of the processes by which the result is achieved. So it is in the case of hypnotism. Actions which have been previously rendered mechanical by long habit are, in the state of hypnotism, performed automatically in response to their appropriate stimuli. There being a strong tendency to imitate movements, these appropriate stimuli may consist in the operator himself performing the movements. Thus when Heidenhain held his fist before his hypnotized subject's face, his subject immediately imitated the movement; when he opened his hand his subject did the same, provided that his hand was visible to his subject at the time. Also, when he clattered his teeth, the hypnotized patient repeated the movement, even though the patient could only hear, and not see, the movement; similarly, the patient would follow him about the room, providing that in walking he made sufficient noise to constitute a stimulus to automatic walking on the part of his patient. In order to constitute stimuli to such automatic movements, the sounds or gestures must stand in some such customary relation to the movements that the occurrence of the former naturally suggests the latter.
Another characteristic of the hypnotic state is that of an extraordinary exaltation of sensibility, so that stimuli of various kinds, although much too feeble to evoke any response in the ordinary condition of the nervous system, are effective as stimuli in the hypnotic condition. It is remarkable that this state of exalted sensibility should be accompanied by what appears to be a lowered, or even a dormant, state of consciousness. It is also remarkable that this exaltation of sensibility does not appear to take place with what may be called a proportional reference to all kinds of stimuli. Indeed, far from there being any such proportional reference, the greatly exalted state of sensibility toward slight stimuli is accompanied by a greatly diminished state of excitability toward strong stimuli. Thus, deeply hypnotized persons will allow themselves to be cut, or burned, or to have pins stuck into their flesh, without showing the smallest signs of discomfort. Heidenhain is careful to point out the interesting similarity, if not identity, between this condition and that which sometimes occurs in certain pathological derangements of the central nervous system, as well as in a certain stage of anæsthesia, wherein the patient is able to feel the contact of the surgical instruments, while quite insensible to any pain produced by the cutting of his flesh. Reflex sensibility, or sensibility conducing to reflex movements, also undergoes a change, and it does so in the direction of increase, as might be expected from the consideration that with the temporary abolition of consciousness the inhibitory influence, which we know the higher nerve-centers to be capable of exerting upon the lower, is presumably suspended. But quite unanticipated is the remarkable fact that the state of exalted reflex excitability may persist for several days—perhaps for a week—after a man has been aroused from a state of profound hypnotism. Thus, Dr. Krener, after having been hypnotized by Professor Heidenhain, and while asleep made to bend his arm twice, for several days afterward was unable again to straighten it, on account of the flexor muscles continuing in a state of tonic contraction, or cramp. In these experiments Heidenhain found that a very gentle stimulation of the skin caused only the muscles lying immediately below the seat of stimulation to contract, and that on progressively increasing the strength of the stimulus its effect progressively spread to muscles and to muscle groups farther and farther removed from the seat of stimulation. It is interesting that this progressive spread of stimulation follows almost exactly Professor Pflüger's law of irradiation. But the rate at which a reflex excitation is propagated through the central-nerve organs is very slow, as compared with the rapidity with which such propagation takes place in ordinary circumstances. Moreover, the muscles are prone to go into tonic contraction, rather than to respond to a stimulus in the ordinary way. The whole hypnotic condition thus so strongly resembles that of catalepsy that Heidenhain regards the former as nothing other than the latter artificially induced. In the case of strong persons this tonic contraction of the muscles may make the body as stiff as a board, so that, if a man is supported in an horizontal position by his head and his feet only, one may stand upon his stomach without causing the body to yield. The rate of breathing has been seen by Heidenhain to be increased fourfold, and the pulse also to be accelerated, though not in so considerable a degree.
In a chapter on the conditions which induce the state of hypnotism, Heidenhain begins by dismissing all ideas of any special "force" as required to produce or to explain any of the phenomena which he has witnessed. He does not doubt that some persons are more susceptible than others to the influences which induce the hypnotic state, and he thinks that this susceptibility is greatest in persons of high nervous sensibility. These "influences" may be of various kinds; such as looking continuously at a small bright object, listening continuously to a monotonous sound, submitting to be gently and continuously stroked upon the skin, etc.—the common peculiarity of all the influences which may induce the hypnotic state being that they are sensory stimuli of a gentle, continuous, and monotonous kind. Awakening may be produced by suddenly blowing upon the face, slapping the hand, screaming in the ear, etc., and even by the change of stimulus proceeding from the retina which is caused by a person other than the operator suddenly taking his place before the patient. On the whole, the hypnotic condition may be induced in susceptible persons by a feeble, continued, and regular stimulation of the nerves of touch, sight, or hearing; and may be terminated by a strong or sudden change in the stimulation of these same nerves.
The physiological explanation of the hypnotic state which Heidenhain ventures to suggest is, that a stimulus of the kind just mentioned has the effect of inhibiting the functions of the cerebral hemispheres, in a manner analogous to that which is known to occur in several other cases which he quotes of ganglionic action being inhibited by certain kinds of stimuli operating upon their sensory nerves.
In a more recent paper, embodying the results of a further investigation in which he was joined by P. Grutzner, Heidenhain gives us the following supplementary information:
The muscles which are earliest affected are those of the eyelids; the patient is unable to open his closed eyes by any effort of his will. Next, the affection extends in a similar manner to the muscles of the jaw, then to the arms, trunk, and legs. But even when so many of the muscles of the body have passed beyond the control of the will, consciousness may remain intact. In other cases, however, the hypnotic sleep comes on earlier.
Imitative movements become more and more certain the more they are practiced, so that at last they may be invariable and wonderfully precise, extending to the least striking or conspicuous of the changes of attitude and general movements of the operator. Professor Berger observed that, when pressure is exerted with the hand at the nape of the neck upon the spinous process of the seventh cervical vertebra, the patient will begin to imitate spoken words. It is immaterial whether or not the words make sense, or whether they belong to a known or to an unknown language. The tone in which the imitation is made varies greatly in different individuals, but for the same individual is always constant. In one case it was a hollow tone, "like a voice from the grave"; in another almost a whisper, and so on. In all cases, however, the tone is continued in one kind, i. e., it is monotonous. Further experiments showed that pressure on the nape of the neck was not the only means whereby imitative speaking could be induced, but that the latter would follow with equal certainty and precision if the experimenter spoke against the nape of the neck—especially if he directed his words upon it by means of a sound-funnel. A similar result followed if the words were directed against the pit of the stomach. It followed with less certainty when the words were directed against the larynx or into the open mouth, and the patient remained quite dumb when the words were directed into his ear, or upon any other part of his head. If a tuning-fork were substituted for the voice, the note of the fork would be imitated by the patient when the end of the fork was placed on any of the situations just mentioned as sensitive. By exploring the pit of the stomach with a tuning-fork, the sensitive area was found to begin about an inch below the breastbone, and from thence to extend for about two inches downward and about the same distance right and left from the middle line, while the navel, breastbone, ribs, etc., were quite insensitive. Heidenhain seeks—though not, we think, very successfully—to explain this curious distribution of areas sensitive to sound, by considerations as to the distribution of the vagus nerve.
Next we have a chapter on the subjection of the intellectual faculties to the will of the operator which is manifested by persons when in a state of hypnotism. For the manifestation of these phenomena the sleep must be less profound than that which is required for producing imitative movements; in this stage of hypnotism the experimenter has not only the motor mechanism on which to operate, but likewise the imagination. "Artificial hallucinations" may be produced to any extent by rehearsing to the patient the scenes or events which it may be desired to make him imagine. A number of interesting details of particular cases are given, but we have only space to repeat one of the most curious. A medical student, when hypnotized in the morning, had a long and consecutive dream, in which he imagined that he had gone to the Zoölogical Gardens, that a lion had broken loose, that he was greatly terrified, etc. On the evening of the same day he was again hypnotized, and again had exactly the same dream. Lastly, at night, while sleeping normally, the dream was a third time repeated.
A number of experiments proved that stimulation of certain parts of the skin of hypnotized persons is followed by certain reflex movements. For instance, when the skin of the neck between the fourth and seventh cervical vertebræ is gently stroked with the finger, the patient emits a peculiar sighing sound. The similarity of these reflex movements to those which occur in the well-known "croak-experiment" of Goltz is pointed out.
A number of other experiments proved that unilateral hypnotism might be induced by gently and repeatedly stroking one side or other of the head and forehead. The resulting hypnotism manifested itself on the side opposite to that which was stroked, and affected both the face and limbs. When the left side of the head was stroked, there further resulted all the phenomena of aphasia, which was not the case when the right side of the head was stroked. When both sides of the head were stroked, all the limbs were rendered cataleptic, but aphasia did not result. On placing the arms in Mosso's apparatus for measuring the volume of blood, it was found that, when one arm was hypnotized by the unilateral method, its volume of blood was much diminished, while that of the other arm was increased, and that the balance was restored as soon as the cataleptic condition passed off. In these experiments consciousness remained unaffected, and there were no disagreeable sensations experienced by the patient. In some instances, however, the above results were equivocal, catalepsy occurring on the same side as the stroking, or sometimes on one side and sometimes on the other. In all cases of unilateral hypnotism, the side affected as to motion is also affected as to sensation. Sense of temperature under these circumstances remains intact long after sense of touch has been abolished. As regards special sensation, the eye on the hypnotized side is affected both as to its mechanism of accommodation and its sense of color. While color-blind to "objective colors," the hypnotized eye will see "subjective colors" when it is gently pressed and the pressure suddenly removed. Moreover, if a dose of atropine be administered to it, and if it be then from time to time hypnotized while the drug is gradually developing its influence, the color-sense will be found to be undergoing a gradual change. In the first stage yellow appears gray with a bluish tinge, in the second stage pure blue, in the third blue with a yellowish tinge, and in the fourth yellow with a light bluish tinge. The research concludes with some experiments which show that in partly hypnotized persons imitative movements take place involuntarily, and persist until interrupted by a direct effort of the will. From this fact Heidenhain infers that the imitative movements which occur in the more profound stages of hypnotism are purely automatic, or involuntary.
In concluding this brief sketch of Heidenhain's interesting results, it is desirable to add that in most of them he has been anticipated by the experiments of Braid. Braid's book is now out of print, and, as it is not once alluded to by Heidenhain, we must fairly suppose that he has not read it. But we should be doing scant justice to this book if we said merely that it anticipated nearly all the observations above mentioned. It has done much more than this. In the vast number of careful experiments which it records—all undertaken and prosecuted in a manner strictly scientific—it carried the inquiry into various provinces which have not been entered by Heidenhain. Many of the facts which that inquiry yielded appear, a priori, to be almost incredible; but, as their painstaking investigator has had every one of his results confirmed by Heidenhain so far as the latter physiologist has prosecuted his researches, it is but fair to conclude that the hitherto unconfirmed observations deserve to be repeated. No one can read Braid's work without being impressed by the care and candor with which, amid violent opposition from all quarters, his investigations were pursued; and now, when, after a lapse of nearly forty years, his results are beginning to receive the confirmation which they deserve, the physiologists who yield it ought not to forget the credit that is due to the earliest, the most laborious, and the hitherto most extensive investigator of the phenomena of what he called hypnotism.—Nineteenth Century.