AUTOMATISM.
TWO PAPERS.—I.
A new-born babe has been defined as a lump of possibilities: it is a mass of rudiments, the unfolding of which constitutes its growth. Butprotoplasm, which, unlike the babe, is a structureless substance, of undefined form and apparently void, is the basis ofalllife, and contains within itself the germs of an infinite development. The microscopist sees in it only a transparent mass, the chemist so many atoms of carbon, hydrogen, oxygen and nitrogen. But while seemingly the same in its chemical constitution, it differs immeasurably in its properties—always distinguished, however, by the soul of unrest that is within it, by its never-ceasing, self-sustained and self-generated movements. Protoplasm makes the saliva which moistens the morsel of bread; protoplasm bides its time in the new-laid egg; protoplasm weaves the tissue of the most highly endowed brain: its agency, in short, is visible in all the meanest and the supremest acts of life. No difference can be detected between its highest and its lowest forms. Yet difference must exist. The most primitive forms of life consist of simple specks of protoplasm, mere masses of organic slime, in which the particles enjoy all the life-functions share and share alike. As the babe develops into the man, so in ascending the scale of life, from the protoplasm of the infusorial amœba to that of a Newton'sbrain, it is step by step along a constant development and separating of dormant powers. There is nothing in the man that was not in rudiment in the babe, and so also does the amœba in its microscopic speck represent the life-power of a universe.
In the separation of the protoplasm for various specific duties very early is a part of it set aside to constitute a so-called nervous system. The simplest form of this system occurs in the sac-like infusoria known as ascidians. This nervous apparatus is composed of a grayish central mass and certain white fibres which radiate from this mass to the outer surface of the sac that constitutes the body of the ascidian. The central mass contains much of very active protoplasm: it is for the ascidian the chief source of all nervous power and action, and is the simplest form of a so-called "nerve-centre." In the higher forms of life the nerve-centre is very complex, but is really formed by superadding small centres, like to the single central nerve-mass of the ascidian, one above the other, and binding them together with innumerable threads of white matter. The white threads seen in the ascidian are the earliest expressions of the white cords of the higher animals which every one knows as nerves. It is the function or office of the gray nerve-centre to originate waves of nervous influence, whilst to the white threads is given the duty of conducting such waves or impulses. The two parts may be well compared to the cells and the conducting wires of a galvanic battery. There are always at least two sets of the nerve-threads or conductors—one leading from the surface of the body to the nerve-centre, and the other from the centre to the exterior of the organism. Those fibres which start from the surface carry impulses to the centre, and are known by the scientist as afferent nerves: in the higher animals they conduct to the centres of consciousness impulses which give rise to sensations; hence they are often known assensorynerves. The nerve-threads which carry impulses away from the centre to the outer regions of the body are known as efferent nerves, because through them motion is produced asmotornerves.
To the primitive organic slime, which is the lowest form of life, consciousness can hardly come. The ascidian with its distinct though simple nervous system is a different and much higher being. In its microscopic world some floating particle touches it roughly: the ever-sensitive end of the afferent nerve thrills; the vibrations pass along the nerve-fibres to the central nerve-mass and provoke it into action: forthwith it sends down the efferent nerve a strong impulse which travels out until it reaches a mass of contractile tissue known as a muscle and causes it to shorten. In the ascidian, however, the limits of nerve-life are very narrow—no eye to see, no ear to hear, no separation of one kind of sensation from another, if indeed there be sensation at all, for we do not know whether the ascidian lives like the plant, to itself unknown, or whether it enjoys a twilight of semi-consciousness, feeling dimly its own existence and that of surrounding objects. The movements which it makes do not seem to emanate from consciousness, but always to originate in the contact of some foreign body with the exterior of its organism. The central mass of nervous protoplasm appears never to flash of its own volition nervous energy to the muscle, but only when aroused by an impulse from without. All movements seem to bereflex—that is, produced by an impulse passing up from the surface along the afferent nerve to the central mass, and thrown or reflected back, as it were, along the motor nerve to the muscle.
Such simple reflex movements occur in all, even the highest, animals as the most primitive expressions of nervous energy. The exigences of lives fuller than that of the ascidian demand, however, other movements, whose complexity is continually increasing as the scale of life is traversed. Keeping pace with this elevation of function is a progressive setting apart of certain parts of the nervous system for certain purposes. In other words, as function or office becomes more complicated and more separate and particular, so also does the anatomyor structure of the nervous system. The whole nerve-life of the ascidian dwells in one cell or central point and a few fibres: that of the man is divided up between some millions of similar cells and fibres, each set aside for the performance of only one act or class of actions. Special powers everywhere require special structure. From the nervous system of the ascidian to that of man is a transition like that from the universal workman of a barbarous society to the complex factory of modern civilization, in which one man does only one little thing, but does this perfectly.
The general structure of the nervous system in all vertebrates from the frog to the man may be thus described: The cerebral hemispheres, orupper brain, a large double central nerve-mass which has no distinct nerves; thelower brain, which is also situated within the cranium, but below the cerebral hemispheres, and is provided with afferent and efferent nerves; and aspinal cord, which springs out of the lower brain and has an abundant supply of nerves connecting it with all parts of the body.
Of these great central nerve-tracts the spinal marrow is the simplest in construction. It is the "silver cord" of the old Hebrew poet, and owes its whitish appearance to the innumerable nerve-like fibres which run up and down or across to bind all parts of the cord together or to pass out from it into the nerves. In the central portions of the spinal marrow is a continuous tract of gray matter which is composed of an infinitude of protoplasmic masses closely resembling the central nerve-mass of the ascidian. This gray matter is indeed a series of such nerve-centres, each capable of discharging energy precisely as the central nerve-mass of the polyp does. The white fibres are the conductors of impulses: during life they are continually occupied in carrying messages to and fro between different portions of the spinal gray matter, or up and down—that is, to and from the brain.
In order to study the functions of the spinal cord the physiologist takes a frog from the ditch and with one sweep of a sharp knife beheads it, or, what is the same thing, severs the spinal cord just as it enters the skull. No pain is produced, or at most a momentary pang. The spinal cord is thus isolated from the two brains, and all conscious sensibility is lost. The heart continues to beat, and life may go on for hours, but all the muscles are relaxed and the whole body is without feeling. Hang the creature up, and the long legs dangle passive and motionless. Bring, however, a cup of strong vinegar slowly upward from beneath the leg, and the moment the irritating liquid touches the toes the foot is drawn up. The parallel of this experiment may be repeated in the hospital ward. Cross the dangling, insensitive legs of that man whose back has been broken by some one of the murderous engines of modern civilization, and strike it smartly just below the knee with the edge of the hand, when out flies the leg; or as the patient lies in bed tickle the soles of his feet and see how they are drawn up, although all sensibility has vanished. Such movements as these in the frog or in the man are evidently similar to the wrigglings caused in the ascidian by the contact of an external bit of matter. They are, in a word, reflex: to produce them an impulse has travelled up the sensory or afferent nerves to the gray matter of the spinal cord, and has been reflected back along the efferent or motor nerves to the muscles.
It is possible that in the ascidian the impulse which causes a reflex movement may be dimly perceived, and therefore awaken some sort of consciousness, but the man whose spinal cord is broken by accident or disease feels nothing below the injury, even if his feet be burnt to a crisp. It is plain that any faculty of consciousness which existed in the central nerve-mass of the polyp has been taken away from the spinal cord of the vertebrate, to be concentrated and perfected within the skull; or, in other words, that in the man, and also in the frog, consciousness and ordinary reflex movements have been separated, the one pertaining to the higher, the other to the lower, nerve-centres.
These unconscious reflex movements are in man of prime importance and frequency. The machinery of conscious movement is far more complex than that of reflex action, and every new cog-wheel, so to speak, involves a loss of time as well as of motion. Most of us do not appreciate the period of time between the willing and the making of a movement, yet the astronomer has to take note of it, and, finding that it varies in individuals, allows for the "personal equation" of the observer. We all recognize that one man is slower than another—i.e.that his physical machinery of thinking and doing moves more slowly than does that of his fellow. Every sportsman must have paralleled a little personal experience of my own. Last fall I shot at a flying quail between which and myself at the time of firing a sturdy oak tree raised its trunk. The bird was put up, aimed at, and the impulse sent by the will to the trigger-finger: before the impulse reached the finger I distinctly recognized that the bird had dodged behind the tree, but the countermand sent by the conscious will to the finger could not overtake the first order, and so, in defiance of my wishes, the gun was discharged.
There are many processes necessary to comfortable human life for which consciousness is far too slow in its operations. Had the eye to wait for conscious perception the dust which whirls in the air would soon blind it; but, as Nature has arranged the mechanism, when the speck approaches the eye the lid shuts instantly through a reflex act, even though the man be unconscious or sight has been lost. It will be noticed that in this movement of the eyelid a purpose is served: it is as though the man perceived the speck and willed to close the lid in order to protect the eye. An action done to serve an apparent end is spoken of by the physiologist as "purposive." It would seem at first that such an action implies consciousness, but it has just been shown that this—in regard to the eye, at least—is not the case, and before this paper is ended it will be demonstrated that adaptation for a useful end is no proof that an action is directed by consciousness.
If, instead of putting the feet of the prepared frog spoken of a few paragraphs back in acidulated water, we drop the irritant upon the thigh, the corresponding foot is raised at once and bent upward so as to brush off the acid. If the foot has been cut off, the bleeding stump will still be bent upward, and if it be too short to reach the irritated spot, then the other foot will be raised and a determined effort be made to remove the offending liquid. All these movements certainly look as though the frog felt the acid and endeavored to get rid of it. Not so, however. Drop this same frog into water which is gradually heated. The batrachian does not try to get out, but sits motionless until he is boiled. Surely, if he felt the drop of vinegar on his foot, much more would he feel the boiling water bathing his whole surface. Curiously enough, if the acid be put upon the leg of the frog while in the water, the movements will be the same as if he were on the table.
These experiments and the experiences of daily life clearly show the truth of the assertion recently made, that the fact that an action has a purpose does not prove its connection with consciousness. If Evolution be correct, there is no difficulty in explaining the doings of the beheaded frog. It is a law governing nervous function that every time an action is repeated the tendency to repeat the action is increased, until at last habit becomes a governing law, and under certain circumstances actions, at first wilful, become unconscious. The first earth-born batrachian, perhaps, felt during the first hour of his existence some irritant on his leg and scratched it away. The next hour the process was again gone through, and so on until the frog was gathered to his fathers. His children found themselves a little more disposed to scratch than was their progenitor; and at last, so well accustomed did the spinal cord become to move the feet when the irritant touched the leg that the motions were carried out without waiting for the will to command, and the particular reflexmovements which astonish the late-born human philosopher became a fixed habit.
In such movements as have been described are to be found the simplest form ofautomatism, the term being used to express the doing of actions which are performed for an end, but in which consciousness plays no part.
Having studied the spinal marrow, the physiologist, leaving this untouched, cuts off the upper brain of the frog, leaving the lower brain in union with the spinal cord, and unharmed. A frog so mutilated, sitting upon a leaf or tuft of grass in a swamp, would be apt to be passed unnoticed as anything extraordinary. He sits perfectly still when approached, but touch him and he leaps off vigorously. If an obstacle be in the way, he does not strike it, but springs above, below or to one side as circumstances may favor. If dropped into the water, he swims as well as ever, and if the water be gradually heated, he soon endeavors to get out. If, as he sits upon a board, the latter be quietly and not too suddenly moved, he does not jump away, but continually shifts his position, so as to maintain the centre of gravity in its proper place and to keep the normal erect posture. Stroke the back of the frog gently and he croaks responsively, as if the titillation called back pleasant memories of caresses received in some lover's tussock-bower. The answer to the stroking is so certain that, as suggested by Goltz, a chorus of brainless frogs might be obtained whose batrachian voices would delight the nerves of old Aristophanes with a triumphal burst ofBrekekekéx! koáx! koáx!
Many other things will the brained frog do—almost enough to convince a superficial observer that the cerebral hemispheres are a luxurious superfluity to the physical and mental well-being of the average inhabitant of the swamp. But no. A little watching shows that for this seemingly intelligent creature past, present and future are alike blotted out. Let the frog alone and it sits motionless, buried not in the profundity of its thoughts, but in the abyss of its thoughtlessness. In the midst of abundance it starves—not, like Tantalus, because it cannot gratify its desires, but because it has no desires to gratify. It feels no hunger, or if it feels hunger seeks no food. A perfect automaton, it moves when touched, it croaks when stroked, it answers to a multitude of external irritations, but when untouched and left to itself it is as a lifeless clod until the sun dries it up and the winds blow it away.
The fish whose cerebral hemispheres or upper brain has been taken away has, like the frog, all conscious perception blotted out, but, unlike the frog, it is in perpetual motion. Stopping not for food, it rushes through the water, avoiding obstacles, but never ceasing its mad race until muscle-power or nerve-force fails because of excessive use and lack of nourishment.
The cerebral hemispheres can also readily be removed from birds. The pigeon so mutilated presents phenomena similar to those offered by the frog. He remains perfectly quiet, balancing himself readily on his perch, but with drooping eyes and sunken head, motionless so long as undisturbed. Move his perch, and he struggles to maintain equilibrium; fire a pistol near him, and he starts, only to fall back at once into his apathy; approach him in the dark with a bright light, and he gazes at the candle with a fixed stare, and sometimes follows its movements with his head; strike at him from the front, and he will draw back; pinch his toes, and he moves. It is therefore plain that he in a certain sense sees, hears and feels. Yet when perishing with hunger he never pecks at the corn which he sees placed before him, and if left alone dies. If, however, the food be placed in his mouth he swallows it eagerly, and by care can be kept alive for an indefinite period.
Removal of the cerebrum has been repeatedly practised also upon the rabbit and the guinea-pig. The mutilated rabbit sits motionless whilst undisturbed, starves in the midst of plenty, cries out with its peculiar pathetic scream when pinched, draws back when ammonia is put to its nostrils; in a word sees, hears, feels in the same sense as does the pigeon,and, like the pigeon, undisturbed remains passive until death. Tread, however, upon the rabbit's foot, and perhaps with a little scream it darts forward in a furious race. Once started, it, like the brained fish, does not stop until exhausted or until it has dashed its head against some obstruction, for, unlike the mutilated fish, it does not have the power of avoiding obstacles.
Such are the phenomena which in the various species of animals follow the removal of the true brain. Many of the acts are seemingly so purposive, and certainly so complicated, as to suggest that they must be conscious. It has, however, been shown that the fact that an act is apparently purposive and complicated does not prove that it originates in consciousness, and certainly in the brainless animal the past, present and future have been blotted out. There is absolutely no conscious memory, else the needed food would be taken when offered and spontaneous movements would occur. It is hard to conceive of consciousness without memory, and it is certain that no purposive act can be directed by consciousness when memory does not exist in any degree or form. If all memory be lost, though consciousness be preserved, that consciousness would not have the knowledge which should enable an animal to perform a complicated purposive act; nor could it acquire knowledge by experience, because each movement would be forgotten as fast as produced. The phenomena exhibited by the brainless animals must therefore rest upon some other basis than consciousness. The first point to be observed in looking for this basis is that movements never occur so long as there is no external irritation. The frog, the pigeon, the rabbit, all maintain the same absolute repose unless the impulse comes from without. The fish is a seeming, but not a real, exception to this rule. The frog, the pigeon, the rabbit, all are quiet on the land, because their surface is not irritated: the fish in the water rushes forward, because the play of the liquid is all the time irritating the exterior of the body. Throw the frog into the water, and it is seized with the madness of the fish; toss the pigeon in the air, and it dashes forward; set the rabbit once in motion, and its course also is a headlong fury. Placed under parallel conditions, these various animals exhibit parallel phenomena, and remain quiet unless disturbed by surface-irritations. The facts show that for action in the animal whose upper brain has been removed some external irritation must generate the impulse, which travels upward to a nerve-centre, and then brings into activity certain masses of nervous tissue (ganglia), which, thus aroused, send impulses out to the various muscles without the intervention of consciousness. Movements generated in this way arereflexorautomatic. In brainless[2]animals the reflex actions are not different in their essence, but only in their degree, from those performed in the frog with a cut spine; or, in other words, the acts originating in the lower brain are reflex and similar to those arising in the spinal cord, only more complicated and more apparently purposive.
The complexity of the reflex movements which are produced through the lower brain indicates a corresponding complexity in the apparatus concerned. In accordance with this, we find that whilst only one kind of nerves capable of carrying impulses from the surface to the nerve-centres enters the spinal cord, to the lower brain pass not less than five distinct varieties of afferent nerves, which carry impulses of as many different characters to the centres. Contact is necessary to arouse reflex movements through the spinal cord. The effect of a pistol report upon a brainless animal demonstrates, however, that its nerve of hearing is capable of carrying to the middle brain an impulse which stirs that centre to action. The brainless pigeon follows with its head the lighted candle: its nerve of sight is therefore capable of taking part in the creation of a reflex movement. The same bird will eat largely when appropriate food is placed in its mouth—an indication that the nerve of taste is also active. In a word, to the middle brainthe nerves of sight, of hearing, of tasting, of smelling, as well as those of common sensibility, bear impulses which find their appropriate nerve-centres and give origin to complicated reflex movements. Partly in the number and variety of the afferent nerves, and partly in the number and variety of the nerve-centres crowded into the lower brain, lie the causes of the great intricacy of the automatic movements which originate in this region.
Of all the acts performed by the brainless frog, fish, bird or mammal, the most difficult to understand are those connected with standing, jumping, swimming, walking, flying, running, etc.; or, in other words, with equilibration, or the function of maintaining the equilibrium. Why does the brainless frog, the automaton, shift his position as the board upon which he sits is slowly tilted? There are apparently no new contacts of the skin: the motion is so quiet, so gentle, that it would seem as if there was nothing to produce irritation of the surface of the body so as to cause reflex acts. If it be true, as is asserted by some observers, that taking off the skin of the legs of the frog (a procedure which causes no pain, as the frog has no consciousness) prevents his shifting himself to maintain his equilibrium when his resting-place is moved, it is plain that the surface-irritations which cause the reflex alterations of position in the brainless frog originate in the skin of the legs and through the sense of touch. There are, however, certain facts which indicate that the impulses under discussion are not of so simple a character.
Before inquiring into these facts it should be observed that there is no movement which the uninjured frog ever performs to restore his equilibrium that the brained frog does not also make with equal promptness. Lay it on its back, on its head, twist its legs into unnatural positions, fix it as you may, so soon as released this unconscious automaton restores itself to its sitting posture. This being the case, it is plain that all the machinery of equilibration must be present in the mutilated frog, and must therefore be situated in the lower brain and its dependencies; and, further, that when the uninjured frog consciously attempts to maintain the erect position or to alter the gait, it simply calls into action the machinery provided for it in the lower regions of the nervous system. What is true of the frog is also true of the man; and the question naturally arises, What is the character of this machinery which the conscious will employs? This apparatus consists of two parts: first, certain exterior parts which are affected by disturbances of the equilibrium, and which when thus excited send up impulses to the lower brain; beyond, certain nerve-centres which when aroused by impulses derived from the external parts send back in a reflex manner impulses to the various muscles, which by their contraction produce motion or rectify the mistakes of position. Touch has much to do with equilibration: sight also has much to do with it. There is a disease of the spinal cord known as locomotor ataxia which destroys the sense of touch in the legs. A person suffering from this disorder is said to be ataxic. When a completely ataxic man puts his feet upon the pavement he feels nothing. Under these circumstances the man is unable to walk with his eyes shut. Even if the ataxia be not complete and some sense of feeling remain, the gait becomes so uncertain that progression is impossible. The pavement feels nearer or farther off than it is, and the result reminds one of his experiences in going up stairs in the dark and stepping out at the top in the belief that another step exists. Long before sensation is completely paralyzed the power of walking in the dark is entirely lost by the ataxic; for, indeed, the man, who has still as much muscular power as ever in his legs, may be unable to walk under any circumstances or even to stand unaided by a cane. The movements are vigorous, but uncontrollable: the legs fly about in all directions, refusing to obey at all the most strenuous efforts of the will.
The loss of the sense of touch in the skin is not, however, the sole or even chief reason that the ataxic man cannot walk. I once saw a patient who could march very well by night or by day, althoughthe skin of his legs was so dead that a live coal would scarcely awaken it. The sense that is wanting in locomotor ataxia is that form of general sensibility which is known as themuscular sense; that is, that sense or feeling which tells the lower brain exactly how much a muscle is contracted, and when to urge it more, when to let it relax. This is evidently a guiding sense, of whose action we are barely conscious, but of whose existence there is no doubt. We do not feel a muscle contract ordinarily, but we do so when attention is directed to a muscle at work. Thus we judge of the weight of a body by the amount of force which our muscles must put forth to lift it. Any one can satisfy himself by a very simple experiment that the judgment of weight is not founded upon pressure on the skin. Lay the hand upon the table, place the heavy body upon it and try to judge of the weight. Again, whenever we endeavor to estimate accurately how heavy a body is, we raise it again and again into the air, evidently that we may feel the muscles contract again and again, and by repeated efforts judge how much of force they put forth.
The phenomena of ataxia are of great importance as corroborating the experimental proofs spoken of a few pages back, which show that walking is automatic and not simply performed by a conscious power of the will. Thus the ataxic may be able to walk with his eyes open, when he cannot even balance himself erect with his eyes shut. If the conscious will really did by a direct effort produce walking, it should be able to control the movements by itself, and the ataxic man should be able to walk although impulses from the exterior of the body no longer reached his lower brain. The man who turns a cog-wheel himself is independent of external power, but the man who directs a clockwork moved by a spring can only push back the stop and release the spring: if the spring be broken he is powerless. The impulses from the exterior are the springs of locomotion, and all the will can do is to withdraw the checks and call the machinery of walking into action. When the external impulses are no longer transmitted to the lower brain walking becomes impossible.
As already shown, general sensibility, including in the term the sense of touch and the muscular sense, is of prime importance in equilibration, but it is unquestionable that the nerves of the other senses carry to the nerve-centre impulses from the external parts of the body which are necessary to the highest development of the function. The partially ataxic man can walk with his eyes open, although he does not feel the floor, because sight replaces touch. The blind man, certainly, cannot balance himself so well as he whose eyes are perfect. We all know that the sight of a yawning abyss or the gazing upon whirling objects is prone to produce giddiness.
Some experiments made by the English physiologist Crum Browne show that there must be guiding impulses which are connected with equilibration besides those already discussed. The observer mentioned found that if a blindfolded man lies on a table with a movable top placed upon a central pivot, he can judge in regard to the movements lateral or vertical, even if they be made so carefully and slowly that the man is perfectly quiescent. The subject under experiment is almost always able to decide correctly not only the direction of the motion, but also the angle through which the motion has extended. It is possible that the guiding impulses under these circumstances originate in all parts of the body. Thus, when we lie with the head downward we are at once sensible of a feeling of fulness or pressure due to the gravitation of the blood and other liquids of the body toward the head. Position undoubtedly affects the gravitation of liquids in all parts of the body: the man whose forces are reduced by a low fever gets a congestion of the back of the lungs if he lies too long upon his back. It may be that this flow of fluids toward any unusually dependent part of the body makes an impression upon the nerves of touch, which pass through all parts of the organism, and that in this way peripheral impulses are generated which reach the lower brain.
On the other hand, the extreme delicacyof perception of movement which some persons evince when laid upon the table-top would seem to require a more delicate apparatus than that just spoken of; and there are many facts which point to a peculiar structure in the inner ear as having connection with equilibration. If in the frog the disk back of the eye be wounded deep enough to affect the nerve of hearing, the creature falls upon one side, entirely deprived of its power of balancing itself. Perfectly similar phenomena are seen not only in the mammals operated upon by the physiologist, but also in human beings, in whom wounds of the nerve of hearing, as well as ruptures of blood-vessels in the inner ear, produce a peculiar vertigo, with staggering and loss of power which have been mistaken for apoplexy. Some years since there was under my professional care a man who had been shot in the face, the bullet passing backward toward the inner ear. In this case there was complete loss of hearing on the injured side, and a peculiar giddiness, with staggering gait similar to that which follows hæmorrhage into the inner ear. The bullet had certainly penetrated into the aural region, and the vertigo was evidently like the deafness due to an injury of the inner ear. In the inner ear of all animals are the so-calledsemicircular canals, which are provided with membranous walls, and are filled with liquid. At the end of each of these canals is an enlargement known as anampulla, upon which is a delicate expansion of nerve-tissue derived from the nerve of hearing. These semicircular canals are so placed that every motion of the head must produce disturbance of the liquid contents of at least one of them, and consequently alterations of pressure on the nervous tissue in the ampulla. The structure and peculiar arrangement of these canals and their contents suggest very naturally that they have some other function than that of aiding in hearing, and that they are in some way connected with equilibration—that they are, as it were, the spirit-levels of the body, and that by the shifting of their contents impulses are constantly sent up to the lower brain to direct it in the maintenance of position. This suggestion is confirmed by the results of experiment: in the pigeon and in some mammals the canals can be readily reached and divided. Such injuries to them are followed by great disturbance of the motor function of the animal, the nature of the disturbance being chiefly dependent on the seat and character of the injury. Repeated somersaults backward or forward, bizarre contortions, spinning around worthy of a whirling dervish, loss of the power of balancing on a moving perch or board, staggering gait,—these and other similar phenomena mark the disturbance of equilibration produced by wounds of the semicircular canals.
The balancing of the body which occurs even in standing, much more that of walking, running or flying, is the result of a very complicated series of movements, numerous muscles antagonizing one another by regulated contraction, so that just the right position may be secured. To preserve the equilibrium innumerable unfelt impulses are continually passing from the eyes, from the semicircular canals, from the various muscles employed, up to the nerve-centres in the lower brain, where they are, as it were, assorted and reflected back as co-ordinated or arranged impulses to all parts of the muscular system, and produce just such contractions as are required for the purposes of equilibration and locomotion. When a child is learning to walk it is simply educating this intricate machinery and developing its latent powers. Very much as the will of man aids a setter in developing the natural instinct to hunt, so does the child's will direct, check and in every way assist the complicated and delicate machinery which presides over locomotion. Perhaps a better comparison is to be found in the drill-sergeant training and educating his squad of men, who at first are utterly unable to obey his will, but who by his reiterated efforts are finally so trained that they move as one piece in strict obedience to his word or go through complicated manœuvres without command. No wonder the child requires so many days of effort to get all its delicate machinery of walking, running,etc. so trained that it works smoothly and without conscious effort of the will. But as the training becomes more complete, the lower brain becomes more and more independent of the conscious will which resides in the upper brain or cerebrum, until at last the automatic action is so perfect that walking without consciousness is possible. Very many of my readers have no doubt in their younger days, when hard pressed with a lesson, walked to school studying as they went, their attention riveted on the book, their feet carrying them along the well-known pathway. Under such circumstances consciousness does not direct progression. Walking in the sleep is only one step beyond this. In the days of Antietam a friend of the writer's, worn out with the forced marching, whilst on guard as a sentinel, erect and soldier-like in posture, slept until the dark lantern of the relief officer appalled him with its sudden flash. Once after a long tramp I myself, laden with a heavy pack, nearing home, trudged in the unconsciousness of sleep along the oft-trodden road. In the cavalry raids around Richmond during our late war it was not very unusual for men and beasts to become so exhausted that both would go to sleep on the homeward night-march when they were straining all their powers to escape. The whole regiment asleep, horses staggering along in loose order, men swaying to and fro in their saddles, when there was a sharp turn in the road it was necessary to post sentinels to waken the passing ranks, which otherwise in the unconsciousness of sleep would have continued right on into bush or brake. Indeed, in one instance that came to my notice a horse with an officer on his back did in this way walk over a precipice some twenty feet high.
With the knowledge which we have acquired the feats of somnambulists are stripped of all mystery. The various accounts of these sleep-walkers vary in regard to the eyes being open or shut, and no doubt the fact also varies, the wanderer sometimes going about with open, sometimes with shut, eyes. In either case the sleeper passes from place to place because the automatic apparatus of locomotion is set in action by a dream, and is perfectly able to perform its function unaided by consciousness. I think it will be found that difficult somnambulistic feats are performed with the eyes open, or, in other words, with every unconscious sense in fullest activity. Most of us have read of, if not witnessed, the perilous walkings of somnambulists over housetops and in difficult places, and wondered that a man in his sleep should be able to pass such narrow ledges with safety. The fact is, that often in these cases the walker escapesbecausehe is asleep. The delicate automatic mechanism presided over by the lower brain when well trained performs its function with marvellous accuracy, while often in times of danger it is baffled by consciousness: fear seizes on its centres and paralyzes their efforts; giddiness whirls it into a fatal slip; conscious will hesitates in its selections and is lost. In the somnambulist all attempt at direction by the will is laid aside, and the clockwork moves along undisturbed, carrying its possessor through deadly peril that sickens him the next day as he looks upon the place over which he has passed and hears the story of his nocturnal wanderings.
Walking is only one of the numerous acts of life, and there are various other automatic actions, commonly mistaken for conscious and wilful, which originate in the lower brain. Enough has, however, been said to illustrate the way in which the lower nervous system works, and some of the more important of these automatic acts not now spoken of will naturally be brought into the foreground in another article, in which it is proposed to discuss automatism in the higher manifestations of passion and thought.
H.C. Wood, M.D.
Footnote[2]The termbrainlessis here applied to animals whose upper brain has been removed.
Footnote[2]The termbrainlessis here applied to animals whose upper brain has been removed.
Footnote
[2]The termbrainlessis here applied to animals whose upper brain has been removed.
[2]The termbrainlessis here applied to animals whose upper brain has been removed.