The duration of hypnotic sleep is as variable as that of its prototype in natural somnambulism. The patient usually wakes spontaneously, after a few minutes or hours. Sometimes, however, the period of insensibility is greatly prolonged. If it be desirable to awaken the subject of experiment, a simple reversal of the movements by which sleep was induced may suffice. The paroxysm may be terminated by almost any sudden and energetic appeal to the senses, like an electric shock, a sudden illumination of the eye with vivid light, or a sharp puff of air upon the face.
The simplest phenomena connected with the hypnotic state are those transferences of cerebral perceptions which have been investigated by the Society for Psychical Research.[92] Certain sensitive persons, when blindfolded, are capable of reproducing with considerable accuracy visual images that have been impressed upon the mind of another. The sensitive subject is blindfolded and placed before a table with pencil and paper. Another person then goes out of the room, and gazes at some kind of drawing, geometrical figure, or other object selected without possibility of collusion with the subject of experiment. This person then returns to the room, and places his hand upon the head of the subject, at the same time fixing his attention upon the mental picture of the object. Presently the blindfolded subject takes the pencil and reproduces on paper a rough drawing of the object in question. In some cases it is found possible to effect this transfer of impressions without actual physical contact,—the agent merely standing behind the sensitive subject and concentrating his thought upon the selected object. Closely akin to this is the method of muscle-reading, popularly known as mind-reading. The sensitive is blindfolded, and then presses against his forehead the hand of the person by whom he is to be guided. Almost immediately a tremor pervades his muscles, and he yields all his movements to the guiding influence of the individual with whom he is in contact. If now an object be concealed in any place that is known to the agent, the concentration of that person’s attention upon the hiding place suffices to direct the “mind-reader,” who immediately drags his companion to the given locality.
The explanation of these phenomena consists in a recognition of the fact that certain persons are gifted with nervous organs which are sensitive and responsive to nervous impulses and muscular movements that are too delicate for recognition by the percipient apparatus of ordinary mankind. The more complicated forms of artificial somnambulism result from the complication and exaggeration of the results of this inordinate sensitiveness through the agency of artificial sleep. As in natural somnambulism, so in the hypnotic state, certain organs become totally anæsthetic, while the sensibility of others is wonderfully exalted. Cutaneous sensation may be completely abolished, and the patient may become utterly insensible to every painful impression. The reflex functions may be either suppressed or exaggerated, and the special senses of sight and hearing may be exalted to the highest degree. While in this condition the hyperæsthetic condition of the brain renders the subject peculiarly susceptible to impressions from the will of another, so that all his actions are obedient to the guiding influence of the person under whose control he has passed.
According to Charcot,[93] three principal types of artificial somnambulism may be remarked among the hysterical subjects upon whom he experimented: (1) the cataleptic, (2) the lethargic, and (3) the somnambulic. Of these the first may be developed primarily by any abrupt and powerful impression upon a sensory organ. Gazing upon a brilliant light, fixing the eyes upon a piece of polished metal, or upon the shining eyes of a second person, the sudden clangor of a Chinese gong, may suffice to induce the cataleptic state. Dumontpallier[94] reports the case of a young woman who accidentally hypnotized herself by gazing into the mirror before which she was dressing her hair. This cataleptic state may also be secondarily induced by merely opening the eyes of a patient in whom a condition of hypnotic lethargy has been previously developed. If only one eye be thus opened, the corresponding side of the body alone becomes cataleptic. Closing the eyes causes the disappearance of this symptom, with complete restoration of the purely lethargic state. During the cataleptic condition the several tendinous reflexes disappear, neuro-muscular hyper-excitability ceases, the skin becomes insensible, but the special senses, particularly those of sight and hearing, maintain a partial activity. In this half-awakened state the senses may become avenues of suggestion from without for the production of movements; but, if left to themselves, the limbs remain motionless.
The lethargic state may be induced by simply pressing together the eyelids of the subject, or by causing him to fix his gaze upon some definite object. The paroxysm begins with a deep inspiration, causing a peculiar laryngeal sound, followed sometimes by the appearance of a little foam on the lips. The eyelids are either wholly or partially closed, and are in a state of continual tremulous motion. The eyeballs are generally turned upwards and inwards. The muscles are completely relaxed. The tendinous reflexes are exaggerated; pressure over a muscle, or upon a nerve, arouses a peculiar contracture of synergic muscles and groups of muscles that are supplied by the excited nerve trunk. The facial muscles, however, do not thus become contractured; they merely contract during the application of the stimulus. If the lethargic subject be rendered cataleptic by opening the eyes, these contractures persist even after waking; and they can only be dispelled by renewing the lethargic state before resorting to pressure upon the antagonistic muscles—the process by which contractures peculiar to this species of lethargy may always be annulled. By the approach of a magnet to a contractured limb, the rigidity may be completely transferred to the corresponding muscles upon the opposite side of the body. If upon a limb of a lethargic subject who has been rendered cataleptic by opening the eyes, an Esmarch’s band be applied, pressure over the bloodless muscles excites no contracture until the band is removed. A contracture is then developed, and it may be transferred to the opposite limb by the approach of a magnet. To this phenomenon has been applied the term latent contracture.
The extraordinary muscular excitability manifested by these subjects is further illustrated by an observation recorded by Dumontpallier.[95] If one end of an India rubber tube, half an inch in diameter, and five or six yards in length, be applied over a muscle in the leg, and if the other end be in like manner connected with a watch, every movement of the second hand will be followed by a slight contraction in the muscle. The same result follows connection with the wire of a telephone; and, if a microphone be introduced into the circuit, the incidence of a ray of light upon the instrument, or even its reflection from the conjunctival surface of the eye of a spectator, will arouse a responsive muscular contraction. Charcot has also seen muscular motion upon the opposite side of the body when a mild galvanic current was applied to the parietal surface of the skull, presumably over the motor centres of the corresponding half of the brain.
During these manifestations of muscular hyper-excitability, there is complete insensibility to pain, but the senses of sight and hearing seem to preserve some degree of activity. The subject, however, does not often exhibit any susceptibility to influence by suggestion.
The somnambulic state may be directly induced by fixed attention with the eyes, by feeble and monotonous excitement of the senses, by passing the hands over the face and arms of the subject, and by many other processes of analogous character. This variety constitutes the ordinary form of hypnotic sleep. It may be very easily developed during either the lethargic or the cataleptic state as a consequence of pressure or of gentle friction upon the top of the head. Thus Heidenhain, in the course of his experiments, caused muscular paralysis by rubbing the scalp. Friction of one side of the head occasioned paralysis of the opposite side of the body without notable affection of the consciousness of the subject. The eyes and the eyelids behave as in the lethargic state. The subject seems to be asleep, but there is less muscular relaxation than in the lethargic variety. There is no exaggeration of the tendinous reflexes, and muscular hyper-excitability is absent. But by lightly touching or breathing upon the surface of a limb, its muscles may be thrown into a condition of rigidity which differs from the contracture of the lethargic state, in the fact that it does not yield to excitement of the antagonistic muscles, though yielding readily to a sudden repetition of the same form of excitement by which it was originally produced. Thus a subject under my own observation who, by pressure upon the eyeballs, was rendered insensible to every form of painful stimulation, would immediately pass into a state of perfect rigidity, if his limbs and body were rubbed for a few seconds with the palm of the hand. While in this condition, if the heels were placed upon a chair and the back of the head upon another, not only could the entire weight of the body be thus supported, but also the additional weight of another full-grown man, sitting upon his body, without causing any more yielding than if it had been a log of wood that was lying across the chairs. From the immobility of the cataleptic state this rigidity differs by its greater degree of resistance to passive motion. Though insensibility to pain may be perfectly developed in this state, there is generally an exalted condition of certain forms of cutaneous sensibility, and of the muscular sense. Strange perversions of other special senses are sometimes remarked. Thus, Cohn[96] discovered that a patient who was naturally color-blind, was able, when unilaterally hypnotized, “to distinguish colors which were otherwise undistinguishable.” Conversely, when the cataleptic state is induced, the healthy eye becomes incapable of discerning colors. Spasm of accommodation is also present, and is one of the earliest demonstrable symptoms of the hypnotic condition.
These remarkable exaggerations and perversions of sensibility have been the cause on the one hand, of much skepticism regarding the verity of the phenomena of hypnotism, and, on the other, of much credulity, extending even to a belief in the existence of supernatural and miraculous powers. The extraordinary character of these experiences is well illustrated by the following letter from Lieut. J. M. Brooke, of the United States Navy, to President Wayland, of Brown University. It may be found in “Wayland’s Intellectual Philosophy.”