The Story of the Mind Part 5

2. The second result of this imitative learning about personality is of equal importance. When the child has taken up an action by imitation and made it subjective, finding out that personality has an inside, something more than the mere physical body, then he reads this fact back into the other persons also. He says to himself: "He too, my little brother, must have _in him_ a sense of agency similar to this of mine. He acts imitatively, too; he has pleasures and pains; he shows sympathy for me, just as I do for him. So do all the persons with whom I have become so far acquainted. They are, then, 'subjects'

as I am--something richer than the mere 'projects' which I had supposed." So other persons become essentially like himself; and not only like himself, but identical with himself so far as the particular marks are concerned which he has learned from them. For it will be remembered that all these marks were at first actually taken up by imitation from these very persons. The child is now giving back to his parents, teachers, etc., only the material which he himself took from them. He has enriched it, to be sure; with it he now reads into the other persons the great fact of subjective agency; but still whatever he thinks of them has come by way of his thought of himself, and that in turn was made up from them.

This view of the other person as being the same in the main as the self who thinks of the other person, is what psychologists mean when they speak of the "ejective" self. It is the self of some one else as I think of it; in other words, it is myself "ejected" out by me and lodged in him.

_The Social and Ethical Sense._--From this we see what the Social Sense is. It is the feeling which arises in the child or man of the real ident.i.ty, through its imitative origin, of all possible thoughts of self, whether yourself, myself, or some one else's self. The bond between you and me is not an artificial one; it is as natural as is the recognition of personal individuality. And it is doing violence to this fundamental fact to say, as social science so often a.s.sumes, that the individual naturally separates himself or his interests from the self or the interests of others. He is, on the contrary, bound up with others from the start by the very laws of his growth. His social action and feeling are natural to him. The child can not be selfish only nor generous only; he may seem to be this or that, in this circ.u.mstance or that, but he is really social all the time.

Furthermore, his sense of right and wrong, his Ethical Sense, grows up upon this sense of the social bond. This I can not stop to explain further. But it is only when social relationships are recognised as essential in the child's growth that we can understand the mutual obligations and duties which the moral life imposes upon us all.

_How to Observe Children, with Especial Reference to Observations of Imitation._--There are one or two considerations of such practical importance to all those who wish to observe children that I venture to throw them together--only saying, by way of introduction, that nothing less than the child's personality is at stake in the method and matter of its imitations. The Self is really the form in which the personal influences surrounding the child take on their new individuality.

1. No observations are of much importance which are not accompanied by a detailed statement of the personal influences which have affected the child. This is the more important since the child sees few persons, and sees them constantly. It is not only likely--it is inevitable--that he _make up his personality_, under limitations of heredity, by imitation, out of the "copy" set in the actions, temper, emotions, of the persons who build around him the social enclosure of his childhood. It is only necessary to watch a two-year-old closely to see what members of the family are giving him his personal "copy"--to find out whether he sees his mother constantly and his father seldom; whether he plays much with other children, and what in some degree their dispositions are; whether he is growing to be a person of subjection, equality, or tyranny; whether he is a.s.similating the elements of some low unorganized social personality from his foreign nurse. The boy or girl is a social "monad," to use Leibnitz's figure in a new context, a little world, which reflects the whole system of influences coming to stir his sensibility. And just in so far as his sensibilities are stirred, he imitates, and forms habits of imitating; and habits?--they are character!

2. A point akin to the first is this: the observation of each child should describe with great accuracy the child's relations to other children. Has he brothers or sisters? how many of each, and of what age? Does he sleep in the same bed or room with them? Do they play much with one another alone? The reason is very evident. An only child has only adult "copy." He can not interpret his father's actions, or his mother's, oftentimes. He imitates very blindly. He lacks the more childish example of a brother or sister near himself in age. And this difference is of very great importance to his development. He lacks the stimulus, for example, of games in which personification is a direct tutor to selfhood, as I shall remark further on. And while he becomes precocious in some lines of instruction, he fails in variety of imagination, in richness of fancy, at the same time that his imaging processes are more wild and uncontrolled. The dramatic, in his sense of social situations, is largely hidden. It is a very great mistake to isolate children, especially to separate off one or two children. One alone is perhaps the worse, but two alone are subject to the other element of social danger which I may mention next.

3. Observers should report with especial care all cases of unusually close relationship between children in youth, such as childish favoritism, "platonic friendships," "chumming," in school or home, etc. We have in these facts--and there is a very great variety of them--an exaggeration of the social or imitative tendency, a narrowing down of the personal sensibility to a peculiar line of well-formed influences. It has never been studied by writers either on the genesis of social emotion or on the practice of education. To be sure, teachers have been alive to the pros and cons of allowing children and students to room together; but that has been with view to the possibility of direct immoral or unwholesome contagion. This danger is certainly real; but we, as psychological observers, and above all as teachers and leaders of our children, must go deeper than that.

Consider, for example, the possible influence of a school chum and roommate upon a girl in her teens; for this is only an evident case of what all isolated children are subject to. A sensitive nature, a girl whose very life is a branch of a social tree, is placed in a new environment, to engraft upon the members of her mutilated self--her very personality; it is nothing less than that--utterly new channels of supply. The only safety possible, the only way to conserve the lessons of her past, apart from the veriest chance, and to add to the structure of her present character, lies in securing for her the greatest possible variety of social influences. Instead of this, she is allowed to meet, eat, walk, talk, lie down at night, and rise in the morning, with one other person, a "copy" set before her, as immature in all likelihood as herself, or, if not so, yet a single personality, put there to wrap around her growing self the confining cords of una.s.similated and foreign habit. Above all things, fathers, mothers, teachers, elders, give the children room! They need all that they can get, and their personalities will grow to fill it. Give them plenty of companions, fill their lives with variety; variety is the soul of originality, and its only source of supply. The ethical life itself, the boy's, the girl's, conscience, is born in the stress of the conflicts of suggestion, born right out of his imitative hesitations; and just this is the a.n.a.logy which he must a.s.similate and depend upon in his own conflicts for self-control and social continence. So impressively true is this from the human point of view that, in my opinion--formed, it is true, from the very few data accessible on such points, still a positive opinion--friendships of a close exclusive kind should be discouraged or broken up, except when under the immediate eye of the wise parent or guardian; and even when allowed, these relationships should, in all cases, be used to entrain the sympathetic and moral sentiments into a wider field of social exercise.

One of the merits of the great English schools and of the free schools of America is that in them the boys acquire, from necessity, the independence of st.u.r.dy character, and the self-restraint which is self-imposed. The youth brought up to mind a tutor often fails of the best discipline.

4. The remainder of this section may be devoted to the further emphasis of the need of close observation of children's games, especially those which may be best described as "society games." All those who have given even casual observation to the doings of the nursery have been impressed with the extraordinary facility of the child's mind, from the second year onward, in imagining and plotting social and dramatic situations. It has not been so evident, however, to these casual observers, nor to many really more skilled, that they were observing in these fancy plays the putting together anew of fragments, or larger pieces, of the adult's mental history. Here, in these games, we see the actual use which our children make of the personal "copy" material which they get from you and me. If a man study these games patiently in his own children, and a.n.a.lyze them out, he gradually sees emerge from within the inner consciousness a picture of the boy's own father, whom he aspires to be like, and whose actions he seeks to generalize and apply. The picture is poor, for the child takes only what he is sensible to. And it does seem often, as Sighele pathetically notices on a large social scale, and as the Westminster divines have urged without due sense of the pathetic and home-coming point of it, that he takes more of the bad in us for reproduction than of the good! But, be this as it may, what we give him is all he gets.

Heredity does not stop with birth; it is then only beginning. And the pity of it is that this element of heredity, this reproduction of the fathers in the children, which might be used to redeem the new-forming personality from the heritage of past commonness or impurity, is simply left to take its course for the further establishing and confirmation of it. Was there ever a group of school children who did not leave the real school to make a play school, setting up a box for one of their number to sit on and "take off" the teacher? Was there ever a child who did not play "church," and force the improvised "papa" into the pulpit? Were there ever children who did not "buy"

things from fancied stalls in every corner of the nursery, after they had once seen an elder drive a trade in the market? The point is this: the child's personality grows; growth is always by action; he clothes upon himself the scenes of the parent's life and acts them out; so he grows in what he is, what he understands, and what he is able to perform.

In order to be of more direct service to observers of games of this character, let me give a short account of an observation of the kind made some time ago--one of the simplest of many actual situations which my two little girls, Helen and Elizabeth, have acted out together. It is a very commonplace case, a game the elements of which are evident in their origin; but I choose this rather than one more complex, since observers are usually not psychologists, and they find the elementary the more instructive.

On May 2 I was sitting on the porch alone with the children--the two mentioned above, aged respectively four and a half and two and a half years. Helen, the elder, told Elizabeth that she was her little baby; that is, Helen became "mamma," and Elizabeth the "baby." The younger responded by calling her sister "mamma," and the play began.

"You have been asleep, baby. Now it is time to get up," said mamma.

Baby rose from the floor--first falling down in order to rise!--was seized upon by "mamma," taken to the railing to an imaginary washstand, and her face washed by rubbing. Her articles of clothing were then named in imagination, and put on, one by one, in the most detailed and interesting fashion. During all this "mamma" kept up a stream of baby talk to her infant: "Now your stockings, my darling; now your skirt, sweetness--O! no--not yet--your shoes first," etc., etc. Baby acceded to all the details with more than the docility which real infants usually show. When this was done--"Now we must go tell papa good-morning, dearie," said mamma. "Yes, mamma," came the reply; and hand in hand they started to find papa. I, the spectator, carefully read my newspaper, thinking, however, that the reality of papa, seeing that he was so much in evidence, would break in upon the imagined situation. But not so. Mamma led her baby directly past me to the end of the piazza, to a column in the corner. "There's papa," said mamma; "now tell him good-morning."--"Good-morning, papa; I am very well," said baby, bowing low to the column. "That's good," said mamma, in a _gruff, low voice_, which caused in the real papa a thrill of amused self-consciousness most difficult to contain. "Now you must have your breakfast," said mamma. The seat of a chair was made a breakfast table, the baby's feigned bib put on, and her porridge carefully administered, with all the manner of the nurse who usually directs their breakfast. "Now" (after the meal, which suddenly became dinner instead of breakfast), "you must take your nap," said mamma.

"No, mamma; I don't want to," said baby. "But you must."--"No; you be baby, and take the nap."--"But all the other children have gone to sleep, dearest, _and the doctor says you must_," said mamma. This convinced baby, and she lay down on the floor. "But I haven't undressed you." So then came all the detail of undressing; and mamma carefully covered her up on the floor with a light shawl, saying: "Spring is coming now; that'll be enough. Now shut your eyes, and go to sleep."--"But you haven't kissed me, mamma," said the little one.

"Oh, of course, my darling!"--so a long siege of kissing! Then baby closed her eyes very tight, while mamma went on tiptoe away to the end of the porch. "Don't go away, mamma," said baby. "No; mamma wouldn't leave her darling," came the reply.

So this went on. The nap over, a walk was proposed, hats put on, etc., the mamma exercising great care and solicitude for her baby. One further incident to show this: when the baby's hat was put on--the real hat--mamma tied the strings rather tight. "Oh! you hurt, mamma,"

said baby. "No; mamma wouldn't draw the strings too tight. Let mamma kiss it. There, is that better, my darling?"--all comically true to a certain sweet maternal tenderness which I had no difficulty in tracing.

Now in such a case what is to be reported, of course, is the facts.

Yet knowledge of more than the facts is necessary, as I have said above, in order to get the full psychological lesson. We need just the information which concerns the rest of the family and the social influences of the children's lives. I recognised at once every phrase which the children used in this play, where they got it, what it meant in its original context, and how far its meaning had been modified in this process, called in a figure "social heredity." But as that story is reported to strangers who have no knowledge of the children's social antecedents, how much beyond the mere facts of imitation and personification do they get from it? And how much the more is this true when we examine those complex games of the nursery which show the brilliant fancy for situation and drama of the wide-awake four-year-old?

Yet we psychologists are free to interpret; and how rich the lessons even from such a simple scene as this! As for Helen, what could be a more direct lesson--a lived-out exercise--in sympathy, in altruistic self-denial, in the healthy elevation of her sense of self to the dignity of kindly offices, in the sense of responsibility and agency, in the stimulus to original effort and the designing of means to ends--and all of it with the best sense of the objectivity which is quite lost in wretched self-consciousness in us adults, when we personate other characters? What could further all this highest mental growth better than the game by which the lessons of her mother's daily life are read into the child's little self? Then, in the case of Elizabeth also, certain things appear. She obeys without command or sanction, she takes in from her sister the elements of personal suggestion in their simpler childish forms. Certainly such scenes, repeated every day with such variation of detail, must give something of the sense of variety and social equality which real life afterward confirms and proceeds upon; and lessons of the opposite character are learned by the same process.

All this exercise of fancy must strengthen the imaginative faculty also. The prolonged situations, maintained sometimes whole days, or possibly weeks, give strength to the imagination and train the attention. I think, also, that the sense of essential reality, and its distinction from the unreal, the merely imagined, is helped by this sort of symbolic representation. Play has its dangers also--very serious ones. The adults sometimes set bad examples. The game gives practise in cunning no less than in forbearance. Possibly the best service of observation just now is to gather the facts with a view to the proper recognition and avoidance of the dangers.

Finally, I may be allowed a word to interested parents. You can be of no use whatever to psychologists--to say nothing of the actual damage you may be to the children--unless you _know your babies through and through_. Especially the fathers! They are willing to study everything else. They know every corner of the house familiarly, and what is done in it, except the nursery. A man labours for his children ten hours a day, gets his life insured for their support after his death, and yet he lets their mental growth, the formation of their characters, the evolution of their personality, go on by absorption--if no worse--from common, vulgar, imported and changing, often immoral attendants! Plato said the state should train the children; and added that the wisest man should rule the state. This is to say that the wisest man should tend his children! Hugo gives us, in Jean Valjean and Cosette, a picture of the true paternal relationship. We hear a certain group of studies called the _humanities_, and it is right. But the best school in the humanities for every man is in his own house.

With this goes, finally, the highest lesson of sport, drama, make-believe, even when we trace it up into the art-impulse--the lesson of _personal freedom_. The child himself sets the limitations of the game, makes the rules, and subjects himself to them, and then in time pierces the bubble for himself, saying, "I will play no more."

All this is the germ of self-regulation, of the control of the impulses, of the voluntary adoption of the ideal, which becomes in later life--if so be that he cling to it--the pearl of great price.

CHAPTER V.

THE CONNECTION OF BODY WITH MIND--PHYSIOLOGICAL PSYCHOLOGY--MENTAL DISEASES.

In the foregoing pages we have had intimations of some of the important questions which arise about the connection of mind with body. The avenues of the senses are the normal approaches to the mind through the body; and, taking advantage of this, experiments are made upon the senses. This gives rise to Experimental Psychology, to which the chapter after this is devoted. Besides this, however, we find the general fact that a normal body must in all cases be present with a normal mind, and this makes it possible to arrange so to manipulate the body that changes may be produced in the mind in other ways than through the regular channels of sense. For example, we influence the mind when we drink too much tea or coffee, not to mention the greater changes of the same kind which are produced in the mind of the drinker of too much alcohol or other poisonous substances. All the methodical means of procedure by which the psychologist produces effects of this kind by changing the condition or functions of the body within itself belong to Physiological Psychology. So he modifies the respiration, changes the heart beat, stimulates or slows the circulation of the blood, paralyzes the muscles, etc. The ways of procedure may be cla.s.sified under a few heads, each called a method.

1. _Method of Extirpation._--This means simply the cutting away of a part of the body, so that any effect which the loss of the part makes upon the mind may be noted. It is used especially upon the brain.

Pieces of the brain, great or small--indeed, practically the whole brain ma.s.s--may be removed in many animals without destroying life.

Either of the cerebral hemispheres entire, together with large portions of the other, may be taken from the human brain without much effect upon the vital processes, considered as a whole; the actual results being the loss of certain mental functions, such as sight, hearing, power of movement of particular limbs, etc., according to the location of the part which is removed. Many of the facts given below under the heading of Localization were discovered in this way, the guiding principle being that if the loss of a function follows the removal of a certain piece of the brain, then that portion of the brain is directly concerned in the healthy performance of that function.

2. _Method of Artificial Stimulation._--As the term indicates, this method proceeds by finding some sort of agent by which the physiological processes may be started artificially; that is, without the usual normal starting of these processes. For example, the physician who stimulates the heart by giving digitalis pursues this method. For psychological purposes this method has also been fruitful in studying the brain, and electricity is the agent customarily used.

The brain is laid bare by removing part of the skull of the animal, and the two electrodes of a battery are placed upon a particular point of the brain whose function it is wished to determine. The current pa.s.ses out along the nerves which are normally set in action from this particular region, and movements of the muscles follow in certain definite parts and directions. This is an indication of the normal function of the part of the brain which is stimulated.

Besides this method of procedure a new one, also by brain stimulation, has recently been employed. It consists in stimulating a spot of the brain as before, but instead of observing the character of the movement which follows, the observer places galvanometers in connection with various members of the body and observes in which of the galvanometers the current comes out of the animal's body (the galvanometer being a very delicate instrument for indicating the presence of an electric current). In this way it is determined along what pathways and to what organs the ordinary vital stimulation pa.s.ses from the brain, provided it be granted that the electric current takes the same course.

3. _Method of Intoxication, called the "Toxic Method._"--The remarks above may suffice for a description of this method. The results of the administration of toxic or poisonous agents upon the mind are so general and serious in their character, as readers of De Quincy know, that very little precise knowledge has been acquired by their use.

4. _Method of Degeneration._--This consists in observing the progress of natural or artificially produced disease or damage to the tissues, mainly the nervous tissues, with a view to discovering the directions of pathways and the locations of connected functions. The degeneration or decay following disease or injury follows the path of normal physiological action, and so discloses it to the observer. This method is of importance to psychology as affording a means of locating and following up the course of a brain injury which accompanies this or that mental disease or defect.

_Results_--_Localization of Brain Functions._--The more detailed results of this sort of study, when considered on the side of the nervous organism, may be thrown together under the general head of Localization. The greatest result of all is just the discovery that there is such a thing as localization in the nervous system of the different mental functions of sensation and movement. We find particular parts of the nervous organism contributing each its share, in a more or less independent way, to the whole flow of the mental life; and in cases of injury or removal of this part or that, there is a corresponding impairment of the mind.

First of all, it is found that the nervous system has a certain up-and-down arrangement from the segments of the spinal cord up to the gray matter of the rind or "cortex" of the large ma.s.ses or hemispheres in the skull, to which the word brain is popularly applied. This up-and-down arrangement shows three so-called "levels" of function.

Beginning with the spinal cord, we find the simplest processes, and they grow more complex as we go up toward the brain.

The lowest, or "third level," includes all the functions which the spinal cord, and its upper termination, called the "medulla," are able to perform alone--that is, without involving necessarily the activity of the nervous centres and brain areas which lie above them. Such "third-level" functions are those of the life-sustaining processes generally: breathing, heart-beat, vasomotor action (securing the circulation of the blood), etc. These are all called Automatic processes. They go regularly on from day to day, being constantly stimulated by the normal changes in the physiological system itself, and having no need of interference from the mind of the individual.

In addition to the automatic functions, there is a second great cla.s.s of processes which are also managed from the third level; that is, by the discharge of nervous energy from particular parts of the spinal cord. These are the so-called Reflex functions. They include all those responses which the nervous system makes to stimulations from the outside, in which the mind has no alternative or control. They happen whether or no. For example, when an object comes near the eye the lid flies to reflexly. If a tap be made upon the knee while one sits with the legs crossed the foot flies up reflexly. Various reflexes may be brought out in a sleeper by slight stimulations to this or that region of his body. Furthermore, each of the senses has its own set of reflex adjustments to the stimulations which come to it. The eye accommodates itself in the most delicate way to the intensity of the light, the distance of the object, the degree of elevation, and the angular displacement of what one looks at. The taking of food into the mouth sets up all sorts of reflex movements which do not cease until the food is safely lodged in the stomach, and so on through a series of physiological adaptations which are simply marvellous in their variety and extent. These processes belong to the third level; and it may surprise the uninitiated to know that not only is the mind quite "out of it" so far as these functions are concerned, but that the brain proper is "out of it" also. Most of these reflexes not only go on when the brain is removed from the skull, but it is an interesting detail that they are generally exaggerated under these conditions. This shows that while the third or lowest level does its own work, it is yet in a sense under the weight--what physiologists call the inhibiting action--of the higher brain ma.s.ses. It is not allowed to magnify its part too much, nor to work out of its proper time and measure. The nervous apparatus involved in these "third-level" functions may be called the "reflex circuit" (see Fig. 2), the path being from the sense organ up to the centre by a "sensory" nerve, and then out by a "motor" nerve to the muscle.

[Ill.u.s.tration: FIG. 2.--_s c mt_ = reflex circuit; _s c sp mp c mt_ = voluntary circuit.]

Going upward in the nervous system, we next find a certain group of bodies within the gross ma.s.s of the brain, certain centres lying between the hemispheres above and the medulla and spinal cord below, and in direct connection by nervous tracts with both of these. The technical names of the more important of these organs are these: the "corpora striata," or striped bodies, of which there are two, the "optic thalami," also two in number, and the "cerebellum" or little brain, situated behind. These make up what is called the "second level" in the system. They seem to be especially concerned with the life of sensation. When the centres lying above them, the hemispheres, are removed, the animal is still able to see, hear, etc., and still able to carry out his well-knit habits of action in response to what he sees and hears. But that is about all. A bird treated thus, for example, these second-level centres being still intact while the hemispheres are removed, retains his normal appearance, being quite able to stand upon his feet, to fly, walk, etc. His reflexes are also unimpaired and his inner physiological processes; but it soon becomes noticeable that his mental operations are limited very largely to sensations. He sees his food as usual, but does not remember its use, and makes no attempt to eat it. He sees other birds, but does not respond to their advances. He seems to have forgotten all his education, to have lost all the meanings of things, to have practically no intelligence. A dog in this condition no longer fears the whip, no longer responds to his name, no longer steals food. On the side of his conduct we find that all the actions which he had learned by training now disappear; the trick dog loses all his tricks.

What was called Apperception in the earlier chapter seems to have been taken away with the hemispheres.

Coming to the "first level," the highest of all, both in anatomical position and in the character of the functions over which it presides, we see at once what extraordinary importance it has. It comprises the cortex of the hemispheres, which taken together are called the cerebrum. It consists of the parts which we supposed cut out of the pigeon and dog just mentioned; and when we remember what these animals lose by its removal, we see what the normal animal or man owes to the integrity of this organ. It is above all the organ of mind. If we had to say that the mind as such is located anywhere, we should say in the gray matter of the cortex of the hemispheres of the brain. For although, as we saw, animals without this organ can still see and hear and feel, yet we also saw that they could do little else and could learn to do nothing more. All the higher operations of mind come back only when we think of the animal as having normal brain hemispheres.

Further, we find this organ in some degree duplicating the function of the second-level centres, for fibres go out from these intermediate ma.s.ses to certain areas of the hemispheres, which reproduce locally the senses of hearing, sight, etc. By these fibres the functions of the senses are "projected" out to the surface of the brain, and the term "projection fibres" is applied to the nerves which make these connections. The hemispheres are not content even with the most important of all functions--the strictly intelligent--but they are jealous, so to speak, of the simple sensations which the central brain ma.s.ses are capable of awaking. And in the very highest animals, probably only monkeys and man, we find that the hemispheres have gone so far with their jealousy as to usurp the function of sensation. This is seen in the singular fact that with a monkey or man the removal of the cortical centres makes the animal permanently blind or deaf, as the case may be, while in the lower animals such removal does not have this result, so long as the "second-level" organs are unimpaired. The brain paths of the functions of the second and first levels taken together const.i.tute the so-called "voluntary circuit" (see Fig. 2).

In addition to this general demarcation of functions as higher and lower--first, second, and third level--in their anatomical seat, many interesting discoveries have been made in the localization of the simpler functions in the cortex itself. The accompanying figures (Figs. 3 and 4) will show the principle centres which have been determined; and it is not necessary to dwell upon additional details which are still under discussion. The areas marked out are in general the same on both hemispheres, and that is to say that most of the centres are duplicated. The speech centres, however, are on one side only. And in certain cases the nervous fibres which connect the cortex with the body-organs cross below the brain to the opposite side of the body. This is always true in cases of muscular movement; the movements of the right side of the body are controlled by the left hemisphere, and _vice versa_. The stimulations coming in from the body to the brain generally travel on the same side, although in certain cases parallel impulses are also sent over to the other hemisphere as well.

For example, the very important optic nerve, which is necessary to vision, comes from each eye separately in a large bunch of fibres, and divides at the base of the brain, so that each eye sends impulses directly to the visual centres of both hemispheres.

[Ill.u.s.tration: FIG. 3.--Outer surface of left hemisphere of the brain (modified from Exner): _a_, fissure of Rolando; _b_, fissure of Sylvius.]

[Ill.u.s.tration: FIG. 4.--Inner (mesial) surface of the right hemisphere of the brain (modified from Schafer and Horsley). In both figures the shaded area is the motor zone.]

Of all the special questions which have arisen about the localization of functions in the nervous system, that of the function of certain areas known as "motor centres" has been eagerly discussed. The region on both sides of the fissure of Rolando in Fig. 3 contains a number of areas which give, when stimulated with electricity, very definite and regular movements of certain muscles on the opposite side of the body.

By careful exploration of these areas the princ.i.p.al muscular combinations--those for facial movements, neck movements, movements of the arm, trunk, legs, tail, etc.--have been very precisely ascertained. It was concluded from these facts that these areas were respectively the centres for the discharge of the nervous impulses running in each case to the muscles which were moved. The evidence recently forthcoming, however, is leading investigators to think that there is no cortical centre for the "motor" or outgoing processes properly so called, and that these Rolandic areas, although called "motor," are really centres for the incoming reports of the movements of the respective muscles after the movements take place, and also for the preservation of the memories of movement which the mind must have before a particular movement can be brought about (the mental images of movement which we called on an earlier page Kinaesthetic Equivalents). These centres being aroused in the thought of the movement desired, which is the necessary mental preparation for the movement, they in turn stimulate the real motor centres which lie below the cortex at the second level. This is in the present writer's judgment the preferable interpretation of the evidence which we now have.