Popular Science Monthly/Volume 31/September 1887/Sleep and its Counterfeits
By A. de WATTEVILLE, M.D.
THE Frenchman, whose long trance or sleep attracted extraordinary attention in the latter part of March and the beginning of April, was commonly spoken of as "the Soho sleeper"; but when we speak of a man "sleeping" for several days or weeks consecutively, it is obvious that we do not use the term in its ordinary sense. We all know by experience what sleep is, and we can not conceive ourselves as sleeping for an indefinite time. Yet it is difficult to draw a line between normal and abnormal sleep; the physiological condition merges by insensible degrees into all kinds of pathological states, known as lethargy, trance, stupor, coma. Through the usual phenomena of dreaming, we pass likewise into those of nightmare, somnambulism, hypnotism, ecstasy, and the like. Yet it is important sharply to define typical instances of these conditions, so as to avoid hopeless confusion in an already obscure field of scientific inquiry, and though we may for the sake of convenience occasionally use the term sleep in the wider sense, yet the distinction between the various states included under it must be kept present to our minds.
From the immense number of strange phenomena observed at the Salpêtrière Hospital in Paris, where this subject of hypnotism, especially in hysterical patients, has been investigated with the greatest care, and where I have had the opportunity of studying it, I shall adduce only such instances as have a direct bearing upon the case of "the Soho sleeper."
It is often possible to distinguish between a somnambulistic, a lethargic, and a cataleptic condition of the hypnotized hysterical subject; and by appropriate manipulations (all based on the theory of influencing the brain-centers by sensory impressions) to make the subject pass from one to another of these states. Supposing we have, by intently staring or by "passes," induced the lethargic state, we find that the muscles and nerves of the subject are in a state of extreme hyper-excitability. If we press through the skin with the finger, or a pencil, upon a nerve-trunk, all the muscles supplied by that nerve are instantly thrown into a state of violent contraction. This contraction, strange to say, may, if unchecked, persist not only during the whole of the period of lethargy, but may last for hours, or even days, after the patient has awoke, and does not then relax even during the inter- val of normal sleep. On the other hand, the rigidity immediately gives way under the influence of gentle stroking of the skin over the contracted muscles.
By catalepsy is meant a condition of suspended psychical manifes- tations on the part of the subject, during which the limbs exhibit no muscular or nervous hyper-excitability, but possess the singular prop- erty, while remaining flexible, of preserving indefinitely any attitude imparted to them; hence the name of " waxy flexibility " given to this condition by old writers. Unlike the rigid spasms of the lethargic muscle, the plastic fixity of the cataleptic limb can not be relaxed by friction over the skin. The aspect of the patient in the two condi- tions, moreover, offers striking differences, the sleep-like immobility of lethargy contrasting vividly with the petrified attitudes of cata- lepsy. In both conditions, however, there often is the same absolute insensibility even to the most painful stimuli. A most remarkable phenomenon may be observed in some instances: by merely opening one eye of the lethargic patient the corresponding side of the body is cataleptized. And so in the same subject these two phases of the hypnotic sleep may coexist side by side, with the fullest display of their contrasted characteristics.
The third condition, that of somnambulism, may easily be brought about by light pressure or rubbing on the top of the head. The hysterical patient then passes into a state somewhat between the lethargic and the cataleptic condition. The muscles have lost the hyper-excitability of the former state, and do not possess the plastic adaptability of the latter. Still they react abnormally to light exter- nal stimuli; if we very gently stroke or blow upon a limb, it becomes somewhat rigid. We can not then relax it by a mere touch as we can in lethargy, and, unlike catalepsy, it offers some resistance when we attempt to move it into a different attitude. Insensibility to pain may persist, but there often is in the somnambulistic phase a singular exaltation of memory and of sensorial perception, which has caused it to be called the "lucid state," and which has been described by the devotees of mesmeric delusions as "second-sight." Our readers will recognize in this description the ordinary "magnetic" or "mesmeric" sleep into which not only hysterical, but many other individuals may be more or less completely plunged by the usual " passes " of operators.
It is especially in the somnambulistic state that the astonishing phenomena of suggestion are observed. By this we mean that the patient in whom every spontaneity is in abeyance, who does not "sleep," and who yet does not move or think, can be so impressed through some sensory channel as to enter upon some definite train of ideas or movements. He is under the control of the experimenter, whose will is his will, so to speak. He is a machine ready to go, but unable to start of itself. There are many different ways of imparting suggestions to a hypno- tized subject; and as, in the other phases of hypnotism, hysterical pa- tients present the greatest variety of manifestations, when subjected to suggestive influences. The most characteristic phenomena are those known as "muscular" suggestions. If we analyze an emotional atti- tude, such as that of sending kisses to a loved person, or that of threat- ening an enemy with the fist and outstretched arm, we notice that the whole frame takes part in the special action. The eyes dilate, the muscles of the face move, and an appropriate play of the features ac- companies the leading gesture. This collaboration of several parts of the body in the production of a common effect depends upon the ex- istence in our nervous system of certain mechanisms subservient to the function of mimetic language or physical expression. Now if in the hypnotized subject we throw a limb into such an expressive attitude, we immediately see the usual concomitants of the movement follow suit; the trunk and other limbs fall into a harmonious posture, the carriage of the head is modified likewise, and the expression assumed by the face and eyes is so perfect as to equal or surpass the best efforts of the most consummate actor. It is difficult for any one who has not witnessed the spectacle to realize the perfection of mimicry reached by the hypnotized hystero-epileptic. The cause of this phenomenon is not far to seek: the impression conveyed by the nerves from the part placed in the attitude has called into action the whole nervous mechanism presiding over the movements generally associated with this attitude. But this is not all. Duchesne has analyzed minutely the anatomy of the expression of the human face, and by means of electric currents localized in certain muscles or combinations of muscles, imi- tated with great success the facial play indicative of the various emo- tions and feelings of the mind. Now if in our subject we likewise electrically stimulate certain muscles, and artificially produce an ex- pression of anger, or terror, or love, or disdain, the corresponding attitude is at once assumed by the neck, arms, and body generally. Those of our readers who have access to the book will find remark- able illustrations of these phenomena in Dr. Richer's beautiful work,* for the accuracy of which all those who have had the opportunity of studying hypnotic manifestations in hystero-epileptics will be ready to vouch.
Whole series of muscular actions may be initiated by appealing to the so-called " muscular sense " by similar methods of suggestion. Thus, if a hanging rope is placed in the hands of the patient, she be- gins to climb with incredible energy and alacrity; when placed on all- fours, she runs in that position all over the room, regardless of knocks and collisions. Or, if the movements of washing with invisible soap be communicated to her hands, she will persist in the mimicry for an indefinite time. It is sometimes difficult to check an action so started
- "Etudes Cliniques sur la Grande HystSrie," second edition, p. 668. except by waking the patient up, or making her pass into lethargy.
The hypnotized patient therefore is much in the state of the frog, which when thrown into a pond, even after its brain has been re- moved, begins to swim on touching the water, aimlessly, automati- cally.
Sometimes a movement repeatedly executed by the operator in front of the patient will be imitated and carried out by the patient until stopped: this is a case of suggestion through the organ of sight. Or more complicated trains of movement may be initiated by present- ing to the patient objects suggestive of certain actions, such as a plate and spoon, a brush and comb, and the like. The sight of a boot will start an endless repetition of putting it on, lacing and unlacing, taking it off, putting it on again, and so forth indefinitely.
The field of suggestions through the ear by means of language is boundless. Such words as "rats," "bird," "flower," wake up a train of imagery in the patient's brain which is immediately projected out- ward in an expressive display of appropriate gestures of aversion or desire, and corresponding movements of avoidance or capture. If in deep hypnotism, the subject is immediately wrapped up in those cre- ations of the imagination; if slightly hypnotized only, repetition of the suggestive words is needed to neutralize the controlling influence of the senses. The ordinary phenomenon of hypnotism, the impossi- bility which the subject feels of escaping the prohibiting influence of a suggestion, belongs to this category. You assure him that he can not move his arm, for instance; he feels that he can, and yet he can not. The volitional current from his higher brain-centers is neutral- ized, as it were, by the current from other centers in which the sug- gestion has created a fixed idea of his own incapacity. As hypnosis becomes deeper, every trace of resistance disappears, and the fixed idea reigns supreme.
Such are the leading phenomena of hypnotism as observed in those highly sensitive subjects, the sufferers from the graver form of hysteria, or hystero-epilepsy. It would take us too far to describe the various symptoms of this form of nervous derangement, which, though com- paratively common in France and among certain other nations, seems to be very rare, at least in its full development, among the Germanic races. In Dr. Richer's work, already mentioned, a full account is given of the appalling violence of the convulsive seizures and of the delirium that characterize the disease. Epidemics of hystero-epilepsy were rife in the middle ages, especially among the members of relig- ious bodies; and even now it seems to be closely related to supersti- tions or mystical beliefs and practices.
Though essentially a disease of the female nervous organization, many instances are found of men suffering from more or less modified forms of hystero-epilepsy. The less striking symptoms of it, such as various forms of paralysis, loss of sensation, loss of speech (aphasia), are often sufficiently developed in male subjects to justify us in class- ing them in the hysterical category of nerve-sufferers.
In this category " the Soho sleeper " deserves to hold a high place, as will become manifest on reading the following condensed resume of his history as given by Professor Charcot, in the " Progres Medical " for March, 1886, and completed by some further details, published in recent numbers of the " British Medical Journal ":
Ch. was born in 1848, and his family history points to a strong neurotic heredity. He served in the French army in Algeria; and during the Franco- German War received a wound in the left elbow which led to amputation of the arm (1871). A few months later he was seized while at supper with uncon- querable drowsiness, from which he could not be aroused. The next morning he broke out into a terrific delirium that lasted two days. A second attack of a similar nature occurred soon after. In 1875 he suffered from strange nervous symptoms, and in 1878 had another attack of sleep, followed by a long period of imperfect articulation. In 1880 he was seized again; and in addition to com- plete loss of speech, there was loss of feeling and movement of the left leg. He remained six months under treatment. Since then there has been a series of relapses, after one of which (1885) he came under the notice of Prof essor Charcot in the Salpetriere Hospital. He was then found to have lost to a great extent sensation on the left side of the body; he could not articulate a single sound, but could express himself freely by writing. He was troubled with nightmare, in which the hallucinations of his former delirious seizures used to recur. He recovered his speech quite suddenly, without passing through a period of stam- mering as on former occasions.
During the fifteen months that elapsed till his arrival in London, he seems several times to have gone through his usual ordeal of sleep, followed by loss of speech and paralysis of the left leg. The attack which he has just had, seems to have been excited by the emotion he experienced on being robbed of all his money (March 24th). The somnolent stage lasted about a fortnight, and was followed with the usual paralytic and aphasic condition. During his torpor his eyes were shut, and his general appearance was that of a man in a profound sleep. He did not react to the loudest sounds; but if a ray of light was cast upon the pupil the eyelids gradually opened, and the eyeballs converged toward the bright object. The results of various experiments made upon the patient in his trance-like state illustrate several of the hypnotic phenomena already de- scribed as observed in hystero-epileptic patients. His muscles presented both the hyper-excitable and the plastic peculiarities that characterize the lethargic and the cataleptic phases respectively of artificially-induced sleep, but with the difference that they both coexisted, whether the eyes were shut or opened. Certain phenomena of suggestion through the "muscular sense" could easily be elicited. For instance, a series of movements imparted to the face, arm, or leg was automatically repeated, and continued for an indefinite time. Again, on imparting to his upper extremity an attitude of menace with outstretched arm and clinched fist, his eyes (previously opened) suddenly turned toward the limb, and he assumed an expression of anger verging on ferocity. I noticed that on interposing an opaque object between the eyes and the arm, the latter speedily relaxed and fell, the eyes closed, and the patient relapsed into his ac- customed slumber.
During the second week of the trance he began to obey orders repeatedly given, such as "Open your eyes," "Sit up," etc., and to answer simple ques- tions by writing. lie could be made to write anything to dictation; but when- ever ordered to indite a letter, he constantly reproduced one ho had written shortly before this attack.
Finally, be was found to have lost sensation in the left side; and the appli- cation of magnets to the skin produced some of the alterations of feeling char- acteristic of hysterical hemianaesthesia. Powerful electrization, though it failed to rouse him up, induced convulsions and spasms, typical of tbe regular hystero- epilectic seizure.
There is thus no doubt left us as to the nature of the case of "the Soho sleeper." Among other instances of attacks of sleep in the course of hystero-epilepsy, I may mention a patient whom Professor Charcot has had under his observation for many years:
She first came to the Salpetriere Hospital in 1862, and presented many of tbe alterations of sensation and movement characteristic of tbe disorder. On April 7, 1875, she was seized with somnolency, which persisted with temporary awakenings till tbe 27th. There occurred then a violent outburst of paroxys- mal laughter and weeping. From that moment the patient passed into a cata- leptic condition, with occasional hysterical fits of the same description. She had to be fed with a spoon; she swallowed as if automatically, with a noise, but without any signs of consciousness. She awoke quite abruptly on the 7th of June, and affirmed that she had no recollection of what had taken place during the past two months. There occurred in 187G another fit of the same kind, that lasted about a fortnight.
In order to illustrate further the intimate connection between cer- tain morbid forms of sleep and the hysterical state, I shall briefly allude to the so-called "hysterogenic" and "hypnogenic" pressure-points discovered by Professors Charcot and Pitres.
A very remarkable phenomenon connected with grave hysteria is the artificial production and arrest of attacks by pressure on certain points on the surface of the body. The number and distribution of these points are very variable, and they differ in every case. They usually can only be found out by careful search, the patients themselves ignoring the existence of them.
On pressure being exerted upon one of these " hysterogenic " spots, the patient falls into a convulsive or tetanic spasm, and the various phases of the attack succeed one another much in the same order as in a spontaneous fit. Now it is a curious fact that a repetition of the pressure on the same spot, or on some other spot experimentally dis- covered, will often abruptly modify or arrest the attack. The great theoretical and practical importance of this singular property of cer- tain circumscribed cutaneous areas, has directed the investigations of several careful observers, and led to the discovery of similar spots, called "hypnogenic," pressure upon which determines, not a muscular spasm or convulsion, but an attack of hypnotic sleep.
These hypnogenic areas are likewise irregular in their number and distribution; and along with them are usually found other spots, usu- ally on the opposite side of the body, pressure upon which awakes the patient. We have here an undoubted argument in favor of the view according to which attacks of sleep in certain hystero-epilep- tics are mere modifications of the typical convulsive and delirious seizure.
The researches of Althaus have led him to formulate the axiom that "nervous diseases are not, as is commonly asserted, more fre- quent, but on the contrary less numerous, in large towns than in the country, and it is probable that their occurrence is powerfully influ- enced by race." He adduces a table in which the percentages of deaths from nervous diseases (as recorded in the Registrar-General's returns) for London, the southwestern counties, and Wales are 10*66, 11-20, 15-38, respectively. He has found that "Wales exceeds all English counties so strikingly in this respect that neither density of population, nor climate, nor difference of occupation will account for that circumstance." He is therefore inclined to attribute this differ- ence to another circumstance, viz., the difference of race a conclu- sion that is borne out in a certain measure by the undoubted greater prevalence of hysteroid symptoms among the Latin, and perhaps also the Slav and other Eastern races, as compared with those of Germanic origin.
It is probably in considerations of this nature that we shall find an answer to the question often asked in this country by those who do not roundly attribute all or most of the symptoms of hystero-epilepsy to shamming or exaggeration, " How is it that such cases never come to our notice? " Is it not because of those racial differences which run deep in the nervous constitution of individuals? At any rate the presence of " the Soho sleeper " among us will, let us hope, modify the somewhat insular skepticism still lurking among medical men on this side of the Channel.
The subject of prolonged sleep and trance is intimately connected with that of apparent death. Though there is no doubt that most of the dreadful tales concerning the premature burial of persons supposed to be dead have no foundation, save in the imagination of the public, we have ample proof of the possibility of such mistakes occurring in the absence of a careful examination of the body. Every one has heard of the fatal tragedy in which the greatest anatomist of his time, Vesalius, played such an unfortunate part. Being called upon, dur- ing his stay in Spain, to perform the autopsy of a patient who had died suddenly, he proceeded to open the body, when, to the horror of the bystanders, at the second sweep of the knife unmistakable signs of life were given!
It is difficult to imagine how in the case of patients subject to cata- leptic seizures, and known by their friends to be so, periods of sus- pended animation, however protracted, could ever lead to premature burial. Pfendler, however, states, that he has known two cases in which a disastrous result was barely averted:
A Viennese lady, who had suffered for a long time from cataleptic or lethar- gic attacks, was finally buried in one of her trances. The sexton, who fortu- nately happened to be a thief in tbis instance, had reopened the grave, and was busy removing her clothes during the ensuing night, when a resurrection of the dead took place. Stricken with terror, ho was running away, when the woman called him back, requesting to be taken to her doctor. The second instance referred to by Pfendler is that of a young lady, aged fifteen, who, after a convul- sive attack, had St. Vitus's dance and other nervous symptoms. Finally she became subject to fits of sleep lasting several days. Her health suffered greatly, and the exhaustion became such that, after a consultation of the first physicians, every hope of her recovery was given up. The next day she suddenly started as if to embrace the attendant who was watching her, and fell back as if dead. All the usual tests failed to detect any sign of life. Finally, funeral preparations were made; she was dressed in white, the bell was tolling. Still uneasy about the absence of any sign of decomposition, Pfendler was making a last examina- tion when he detected a faint respiratory movement. After an hour and a half's friction and stimulation, movement returned; and the patient looking about and smiling said, "I am too young to die." She then fell into a sleep of ten hours' duration, and woke up in full convalescence. The patient in this case had never lost consciousness, and remembered afterward what had been said and done in the room during the medical consultation and funeral preparations.
Catalepsy, though intimately allied to hysterical neurosis, often oc- curs in patients who offer no other symptoms of nervous derangement. Emotions are often the exciting cause of an attack in a cataleptic sub- ject. Many curious instances are related by authors:
A little girl, mentioned by Tissot, shocked at her sister having helped her- self to a coveted morsel, remained stiff and motionless for an hour, a spoon in her hand, and her arm outstretched toward the dish. A soldier, quarreling with a companion, in a fit of passion seized a bottle to throw at him; cataleptic rigid- ity fixed him in this attitude, motionless, unconscious, his eyes full of anger and defiance. In another case, a magistrate on the bench, insulted in the middle of his summing up, remained as if petrified in an attitude of indignation and threat at his insulter. Again, we read of priests being cataleptized at the altar in the attitude of elevating the sacrament.
It is certain that many of the saintly women in the Roman Catho- lic hagiology were victims of this disease: St. Catherine of Siena, I St. Elizabeth of Hungary, St. Theresa; not to speak of Joan of Arc, Madame Guyon, Marie Alacoque, and many others. Cataleptic seizures were also a common feature among the victims of the great hystero- epileptic manifestations so common in the middle ages, which we find described as "possessions" in the curious and abundant literature of the subject.
Among the sickening descriptions of the awful episodes known as "the possession of the Ursulines of Loudun," we find a graphic de- scription of cataleptic phenomena: The devil, enemy of Sister Claire, appeared at the command of her ordinary exorcist, Father Eliz6e, and rendered her supple and ductile like a sheet of lead. The exorcist hent her hody in various directions forward, backward, laterally so that she almost touched the ground with her head. The demon kept her in the posture in which she had been placed until she was moved again, during which time she only slightly breathed through the nose and was insensible, for the father pierced a fold of her skin with a pin without drawing blood or pro- ducing pain. We also read of others who were "remarkable for their pliability. In their sleep they could be manipulated like a sheet of lead, and preserved the postures imparted to them until moved again." Elsewhere a nun possessed by the demon Cismond lay on the ground in a strange trance; her arms and legs could be twisted about as if made of wool; nothing could be extracted from her; the devil keeping her in this condition so as to prevent her confession.
Though, as already mentioned, the Latin races appear to offer a much more favorable field for the spread of nervous epidemics, we read that England has not always been free from such manifes- tations:
"During "Wesley's sermons at Bristol," says Dr. John Chapman, in his work " On Christian Revivals, their History and Natural History," "many used to fall as if struck to the heart by the word of God. Men and women by the score were lying on the ground, insensible like dead bodies." Singular nervous acci- dents were likewise frequent among the American fanatics known as Shakers or Jumpers, as well as among the Irish revivalists of Ballymena.
As late as 1861, at the village of Morzine, a secluded commune in the Alps of Savoy, there occurred a curious epidemic of hysteria with all the characters of "demoniacal possession." The population of these regions is extremely neurotic and superstitious. In a short time nearly all the female population, excited by the exorcismal practices of the clergy, fell a prey to the disease, and the scenes recalled the worst days of Loudun. But at the beginning, when young girls were chiefly affected, phenomena of ecstasy, catalepsy, and somnambulism prevailed. The Government had finally to interfere, and the tempo- rary dispersion and seclusion of the patients speedily restored their mental equilibrium, and the locality has since resumed its habitual tranquillity.
As an instance of trances of a more contemplative tendency, I shall give a short account of Louisa Lateau, of whose attacks Dr. Lefebvre has given a good description:
She used to pass into that condition without any warning. Suddenly, during a conversation, or at her sewing-machine, she would become as if transfixed, the eyes turned upward to the light. " Her expression is then one of deep atten- tion or of distant contemplation. Her physiognomy, like her attitude, often changes, and depicts feelings of joy or of sadness. Sometimes terror is ex- pressed, or she turns slowly, as if watching the progress of an imaginary pro- cession. Sometimes she stands, resting on the tips of her toes, with her hands outstretched, as if to fly away. Her lips move, the eyes brighten, and her face is illuminated by an ideal beauty. The stigmata in her forehead and hands bleed. . . . She kneels, falls face forward to the ground, where she remains for hours in the attitude of crucifixion. Other attitudes are taken during the ecstatic con- dition, which comes to an end in the midst of alarming symptoms of impending death."
I will, in conclusion, venture upon a few suggestions as to the ex- planation of the phenomena of hypnotism and its allied states.
Our cerebral life depends upon the associated activity of innumer- able nerve-cells grouped into clusters or centers, each center being more directly related with some sensory or some motor function. Thus there are visual centers, auditory centers, tactile centers, which form the terminal stations of the nerve-fibers leading from the organs of sight, hearing, and touch. There are also so-called motor centers, the nervous discharges from which, traveling down to the spinal cord, determine movements of the head, trunk, and limbs.
A network of the finest nerve-fibrils of astounding complexity brings the individual cells of each center into relationship with one another, and with the cells of the other centers. This physical asso- ciation of our brain-elements is the material substratum of the psychi- cal process of association of ideas which forms the groundwork of our intellectual life. All the higher manifestations of mind are correla- tives of the harmonious co-operation of numerous brain-elements. Even what appear to be simple states of consciousness are often the result of association. Hence any disturbance in the mutual equi- librium of the cerebral centers speedily leads to alterations of those resultants of forces of which perception, thought, will, emotion, are the subjective manifestations.
One of the most striking properties of the nervous system is that by which the activity of one portion may be arrested or prevented " inhibited "by the activity of another. To give a familiar instance, the action of the respiratory centers is suddenly inhibited by certain excitations of the sensory nerves, as we have all experienced on re- ceiving the first splash of a cold shower-bath. In the cerebral sphere, inhibition of one tract by another is the mechanism which lies at the root of the higher exercise of our faculties."When we choose, for instance, or exercise will-power, the corresponding state of our nervous organism is one involving more or less complex inhibitions. The sense of moral effort is the subjective equivalent of powerful inhibitions of brain-tracts in a state of high tension. The power of mental concentration rests likewise upon similar inhibitions. When we at- tend closely to a sensory impression, or to a train of thought, the ex- citability of every part of the brain except that actually engaged in the act is diminished by an inhibitory action of the working portion. Thus, when wo say that anger or fear paralyzes, we allude in very accurate language to the inhibitory influence which powerful emotion exercises upon the other cerebral functions.
I have said that physiological sleep can be induced by certain monotonous impressions from without. The same may be said of an order of stimuli that has hitherto not received its due share of atten- tion. I mean the afflux of those confused, mostly unfelt, impres- sions from the viscera and tissues generally. Under certain condi- tions after a meal, for instance these may set up, in the cerebral centers to which they converge, an excitation that leads to an inhibi- tion of the higher brain-regions, and so to a state of sleep.
Similar considerations will assist us in explaining the effect of the usual methods of hypnotization. The stimulation of one of the cere- bral sensory centers by repeated gentle and monotonous sounds or touches, or, in the case of the visual organs, by the convergence of the eyes and persistent gazing at a small object, so interferes with the activity of the higher centers as to lead to various perverted motor aud mental manifestations. Certain " nervous " individuals, but above all hysterical subjects, are more amenable to these effects than are others. Repetition in all cases increases the liability to hypnotiza- tion, and in extreme cases the recollection of the processes previously used becomes sufficient to induce sleep. Finally, there are subjects, such as "the Soho sleeper," in whom, owing to the extreme instability of their cerebral equilibrium, a kind of spontaneous hypnotization may be observed.
It would be premature, in the actual state of our knowledge, to speculate upon the nature of the changes in the nervous system upon which the phenomenon of inhibition depends. It has been ingeniously compared to that of the mutual interference of two rays of light or two waves of sound. But this analogy does not account for all the facts; and in connection with this topic we may mention the views recently propounded by Professor Brown-Sequard upon what he calls nervous "dynamogeny." It is a well-known fact that under the influ- ence of various sensorial or emotional stimuli, of moderate intensity or pleasurable quality, our nervous energy, as measured by the muscular effort we are enabled to put forth, is increased to a considerable ex- tent. Recent researches by Dr. Fere have thrown additional light upon these " dynamogenic " or " force-producing " processes, of which the reviving effect of smelling-salts is a familiar illustration. In this instance a diffusive wave invades the whole brain from the olfactory centers, and produces such a change in its constituents as to restore its functions. It has likewise been shown that every form of mental activity is accompanied with increased nerve-power as directly meas- ured by the squeeze of the hand on the dynamometer. It would thus seem that nervous cell-matter is liable to undergo certain modifica- tions under the influence of various impressions derived from other nerve-regions, in virtue of which it becomes more powerful. But, with- out even attempting to define more closely the " dynamogenic " change, we may perhaps assume it to be the counterpart of what takes place in inhibition, and describe the latter as a nervous process in which a group of nerve-cells so acts upon another group as to lower its capacity for work.
Inhibition in one nervous sphere is often accompanied with dynamogeny in another: the removal of cerebral influence, for instance, exalts the autonomy of the spinal cord. A good instance of the co-existence of the two processes is found in "expectant attention," which depends upon the high tension of the centers involved in anticipating the phenomena, with a corresponding inertia of the others. The reader will readily perceive how similar considerations may be employed in the elucidation of such phenomena as ecstasy, suggestion, muscular hyper-excitability, and intensified perception. — Fortnightly Review.