The education of the central nervous system; a study of foundations, especially of sensory and motor training

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Preface

The old theory that education consists solely in modifications in an immaterial entity has worked untold damage. It was argued that the immaterial never grew old, and that it could be trained as well at one time as at another. From this mistaken notion arose such adages as, " It is never too late to be what you might have been." It would be nearer the truth to say of any creature whose higher knowledge rests upon sensory foundations, or, in other words, upon modifications in nerve cells : " It is always too late to be what you might have been." Education may be something more, as the writer believes, than modifications in the central nervous system, but it is also true that without these modifications no mortal can be educated.

If brain cells are allowed to pass the plastic stage without being subjected to the proper stimuli or training, they will never fully develop. The majority of adults have many undeveloped spots in their brains.

This book calls attention to the importance of early purposive training of the central nervous system while its brief morning of plasticity lasts. Then, and only then, can the nerve cells be made lifelong friends, who will take upon themselves the duty of pronouncing correctly, of speaking grammatically, of making habitually correct responses to the viii PREFACE

thousand and one demands of life, while the intellectual powers are left free to devote their entire energies to weightier matters. Such nerve cells will also be ready to reproduce their former sensory experiences as a firm foundation for thinking about concrete things. Rightly trained nerve cells occupy a position analogous to that of a trusty servant, who, without being looked after, attends to all the wearying details of housekeeping, leaving the mistress free to entertain her friends and to develop her higher powers. No human being knows a more relentless enemy than motor nerve cells which have been wrongly trained early in life. Such a man may be worth a million, but the bad grammar will continue to flow automatically from the motor mechanism of speech, and to mortify him in good society.

It has been known for some time that the higher processes of thought are dependent on modifications in brain cells, and that the highest intellectual superstructure can be no firmer than the sensory foundation, but this knowledge has not been properly applied in training these cells. Practical application of truths lags far behind a theoretical knowledge of them.

The principal object of this book is to prescribe for our complex central nervous systems at the proper time the special kinds of exercise, sensory, motor, and ideational, demanded for full development. A person who has only one or even two senses properly trained is at best a pitiful fraction of a human being. The writer has endeavoured to present herewith some facts which every parent and teacher must know and apply in order to secure the fuller development of children at a critical time.

A special feature of this work consists in showing that recalled images of sense objects are powerful and necessary

PREFACE ix

aids in further modifying and developing the sensory cells ; not images of sight alone, but of every sense.

Many examples of sensory objects have been taken from literature to indicate the proper direction for training. Theory often fails because objects demanding constant practice are not at hand or suggested. Almost all study English literature, which constantly presents objects requiring sensory interpretation for their proper understanding. For this reason, numerous examples, especially from Shakspere and Milton, have been quoted to show how the study of literature may be made to react on sensory training. From long personal experience, the author can testify that the majority of pupils can soon be induced to seize the first opportunity to obtain definite sensory knowledge of any object mentioned in poetry, whether of a daffodil, of a murmuring pine, or of " incense-breathing morn." It is hoped that the chapter on " How Shakspere's Senses Were Trained " may be found practically serviceable in educating the central nervous system of youth.

It has been the aim of the author to restrict this work to its own proper field of training and developing the central nervous system, and not to offer these chapters as a substitute for the thorough study of psychology.

Acknowledgment is made to Professor Donaldson's excellent work, The Growth of the Brain, — although the following chapters do not view the subject in as fatalistic an aspect as that work, — and to Dr. August Schachner for much scholarly help in dissections of the central nervous system.

R. P. H.

Chapter I

Anatomical and physiological details are usually uninteresting except to physicians and to a few other specialists. It is the purpose of this chapter to give only those facts necessary to render more intelligible what we have to say about the training of the central nervous system. An anatomical or a physiological fact is utterly worthless unless it can be assimilated to other ideas to render them more clear. When we come to speak of undeveloped brain tracts, the terms will mean little, unless we can construct definite images of the various cerebral areas. But if we know precisely what part of the brain is undeveloped, the necessity for its improvement will be more forcibly realized, and directions for the proper exercise will lay a stronger hold on the attention.

The mind insists on investing all its knowledge with two primal relations, those of space and time ; the where and the when are questions instinctively asked. A gentleman who had often heard the Turkish question and the approaches to the Black Sea discussed, was haunted by a sense of unrest whenever he heard the Dardanelles and the Bosphorus mentioned. Occasionally the term " Hellespont" was used, and he did not know with which strait to identify that name. He was neither sure of the exact position of Constantinople, nor of the bodies of water which the straits connect. Finally he could no longer endure the mental disquiet over the ignorance of the spatial relations, so he consulted an atlas, formed an image of a gourd with two handles, — the longer handle being the Dardanelles or Hellespont, the body of the gourd the Sea of Marmora, the shorter handle the Bosphorus, — and felt a sense of relief in having satisfied a primal demand of the mind. In the same way the mind demands a map of the central nervous system before remarks about developing certain parts can be fully realized. An idea as rude as that of the gourd in the case just mentioned is far better than an idea without form and therefore essentially void.

When we speak of developing certain parts of the brain, or of lack of development in certain tracts because of deficiency of early training, we may be said to assume the theory of definite cerebral localization, as opposed to the dynamic or vibratory theory. We wish here to call attention to the fact that these theories, within certain limits, are not necessarily in conflict with each other. It may be true that certain dynamic combinations or vibrations in the same part of the brain may mean different things, just as different rates of vibration in the same ether may cause heat, light, and electricity. But even dynamic combinations or differing rates of molecular vibration must have a local habitation in the brain. If any special tract is not early subjected to all the dynamic combinations or vibrations of which it is capable, that tract is in so far undeveloped.

It may be true that the same fingers can play the piano, grasp a knife, lift a weight, or paint a picture, but it is also true that the muscles in the fingers cannot do the work of the jaws or the legs, nor can the ear take the place of the eye. The muscles in one part of the body may be well exercised and strong, while those of another part may be comparatively little used, and hence weak. The fact that the body is a unit and that the same blood courses to all parts of it, must not cause us to shut our eyes to these undoubted facts of localization of function. We know that special exercise develops special muscles. We also know that, if the sense of sight is trained, while hearing receives no education, the brain tract correlated with hearing will not be proportionately developed.

As organisms grow more complex, there is more specialization of function. Some of the lower forms of animal life may have what answers for a stomach wherever nutriment happens to come in contact with the body, but this is not true of the higher forms of animal life. This greater differentiation with advanced forms of life entails new responsibilities in demanding the proper exercise for the more complex parts, not one of which must be neglected.

The best authorities agree that nerve matter shows increasing specialization with advancing intelligence. Dr. M. Foster says : " Thus when we survey a series of brains in succession, from the more lowly frog, through the bird, the rabbit, the dog, and other lower mammals up to the monkey, the anthropoid ape, and so to man himself, we find an increasing differentiation of the cerebral cortex, by which certain areas of the cortex are brought into special connection with certain skeletal or other muscles in such a way that stimulation of a particular portion of the gray matter gives rise to a particular movement and to that alone." 1 Professor Donaldson says : " Experi-

1 Foster's Text-book of Physiology, p. 749.

merit shows that in man the special cortical centres are somewhat separated from one another, and this separation is due to masses of brain substance which do not give reactions upon ordinary electrical stimulation." 1 We allude to these facts here, since the insistence of special forms of exercise to develop the complex central nervous system is the chief purpose of this work.

The central nervous system, which we shall now proceed to map out, is composed of the encephalon, or contents of the skull, and the spinal cord. All masses of nerve matter, as soon as they leave the brain or spinal cord, are called the peripheral nervous system. The central nervous system is therefore what we popularly mean by the brain and spinal cord.

This system consists of nerve cells and fibres, the latter being in every case the outgrowth of cells. Different cells in varying parts of the body are connected by nerve fibres, in much the same way that New York is connected with Chicago by telegraph wires. The analogy is more striking than appears at first sight because after nerve fibres leave a cell, they have never been seen, even with the strongest microscope, to enter another cell. There is some mysterious physiological, but no anatomical, connection. When a New Yorker telegraphs a man in Chicago, the home of the resident of Chicago may be at some distance from the ending of the wire. A person from another planet might wonder for a long time how the despatch could reach the person, just as we are now wondering how an impulse from one nerve cell reaches another. There is probably some intermediate conductive matter which does the work of transmission in a way analogous to that of the telegraph boy.

The cells of the central nervous system are chiefly composed of a wonderful protoplasmic matter in which minute granules 1 Donaldson's The Growth of the Brain, p. 265.

and striations can be detected. We are not acquainted with any substance which is more sensitive to the most delicate stimulation, or which better retains modifications due to past experience. There are instruments which can detect a change in the brain, caused by the passing of a cloud over the sun. An old man said that his brain cells still retained modifications from a glance at a rainbow on a certain summer's evening,

Fig. 1. — "A group of human nerve cells drawn to scale X 200 diameters. A, cell from ventral horn of spinal cord ; B, cell from the spinal ganglion of dorsal root, with its nerve process ; C, cell from the column of Clarke ; D, solitary cell from the dorsal horn of the spinal cord ; E, cross-section of a large nerve fibre; F, granule cells from the cortex of the cerebellum." — DONALD- SON, after Waller.

seventy years before. Man's entire central nervous system is computed to have at least three thousand million nerve cells. These vary in diameter from about %to to 35 ^0 °f an mcn -

Nerve cells have the power of sending out processes which we term nerve fibres. It is their function to connect all the nerve cells in the various parts of the body. Just as a prosperous country is threaded with telegraph wires, which keep all its cities aware of what is happening elsewhere, so the human body is traversed by nerve fibres which report stimuli, transmit impulses to movement, and perform various other offices connected with the nutrition, circulation, and secretions of the body. Some idea of the fineness of these fibres may be gained from the number of sensory nerves that end in the brain. Specialists estimate this number at not less than two and one-half millions.

There are two classes of nerve fibres, afferent and efferent, those concerned in transmitting stimuli of any kind to the central nervous system and those engaged in bringing impulses from it. We are here concerned with only one species of the class of afferent nerves ; namely, sensory nerves. These transmit any kind of sensory stimulation, such as sound, light, or odour. The only species of efferent nerves in which we are at present interested are motor nerves, or those which transmit impulses to move the muscles. Our entire intellectual life rests on a foundation of sensation and movement.

As soon as we have a sensory nerve leading to a nerve cell, in the spinal cord, for instance, and a motor nerve issuing from the same' cell, we have the elements concerned in reflex action, which is so important in human life and education. Reflex action is simply a sensory impulse turned back along a motor nerve by a nerve cell. If we touch or slightly pinch the hand of a sleeper, it will be withdrawn without his waking. A sensory nerve reports the stimulus to a nerve cell in the spinal cord, and this cell changes the direction of the impulse, sending it back along a motor nerve to the muscles concerned in moving the hand and causing contraction in them. Reflex action may take place without consciousness or brain intervention. Were it not for reflex action, we could make but comparatively little progress in life. We should then be in a position similar to that of the manager of an industrial concern, who could not answer a single letter or transact any business by deputy. He could do no more business than his limited time would allow him to oversee personally. Reflex action is the deputy of the brain, and directs myriad movements, thus leaving the higher powers free to attend to weightier things. Nerve action of this kind is so very important that we shall consider it at greater length in the next chapter. Suffice it for the present to say that so great a physiologist as Dr. M. Foster declares that reflex action can be modified by training.

Thus far we have been considering the units common to the entire central nervous system, — nerve cells and their outgrowth, nerve fibres. We may now consider the individual members of this system, and turn our attention first to the spinal cord, the great organ of reflex action.

The spinal vertebrae pass down the rear median part of the trunk of the body for about a foot and a half, and enclose a remarkable cord of nervous matter. The spinal cord is composed of a gray and a white substance, and, like the brain, is almost divided into two parts. Two deep fissures, an anterior and a posterior, nearly meet, leaving two crescents of gray matter connected by a narrow bar.

The spinal cord gives off thirty-one pairs of nerves which supply the trunk and limbs. The nerves leave each half of the spinal cord in pairs, passing out from the tip of each crescent of gray matter. The anterior and the posterior bundles of nerves combine to form one nerve trunk, soon after leaving the spinal cord.

The motor nerves leave by the anterior horns, the sensory, by the posterior horns, of gray matter. The motor nerves pass to the muscles and transmit to them incentives to movement. The sensory nerves extend to the skin. There is probably not a city in the world that has as many telegraph wires entering it as there are nerves in the spinal cord, leading to the brain. The anterior roots of a frog's spinal nerve were found by actual count to contain from 5,000 to 11,000 separate nerve fibres, the number varying with the size and age of the frog. When the cord is sufficiently injured, the portions of the body sup-

Fig. 2. — Different aspects of sections of the spinal cord and of the roots of the spinal nerves from the cervical region : 1, different views of anterior median fissure ; 2, posterior fissure ; 3, anterior lateral depression, for anterior roots ; 4, posterior lateral depression, for posterior roots ; 5 and 6, anterior and posterior roots, respectively; 7, complete spinal nerve, formed by the union of the anterior and posterior roots. — HALLECK's Psychology, from ALLEN Thompson.

plied with nerves leaving the cord below the seat of the injury suffer both motor and sensory paralysis. Such a limb would have no power to move, and it might be sawed off without pain. The brain's chief deputy is the spinal cord, which, through its powers of reflex action, attends to much of the routine business of the body, leaving the energy of the brain more free to expend itself in other directions.

Passing next to the encephalon, or contents of the skull, we may distinguish between the medulla oblongata, the cerebellum, and the cerebrum. These three form the major divisions of the contents of the skull. There are in addition some smaller basal ganglia, which it is not necessary to describe here.

The medulla oblongata is really the enlarged upper end of the spinal cord. The medulla, which is only about an inch and a quarter long, is an organ of greater complexity than the spinal cord and is capable of a greater variety of actions. The innumerable fibres from the cord pass through it, and many of them here decussate, or cross to the opposite side. Thus, a motor fibre in connection with the right foot would pass over into the left half of the medulla and end in the left side of the brain. Reflex centres of a high order are found in the medulla.

Next comes the cerebellum, or little brain, which is situated at the rear part of the base of the cerebrum, or larger brain. The cerebellum is concerned in some unknown way with coordinating the muscles and balancing the body. If we could, with an eye manifold finer than the finest microscope, look at the cerebellum of a man staggering under the effects of strong drink, we should probably be able to find traces of disorder there.

The cerebrum occupies the upper part of the skull. It is not necessary for our purpose to know all the minute anatomy of the brain, but we must so map it out as to be able to understand what is meant by the development of its various parts.

The brain is divided into two symmetrical hemispheres, the right and the left.

The first landmarks to be learned on the outer surface of the brain are the fissure of Rolando and the fissure of Sylvius. The fissure of Rolando extends from the middle upper part of the brain downward and forward, passing a little in front of the ear, and stopping before reaching the fissure of Sylvius. This latter fissure begins at the base of the brain and runs back-

Fig. 3. — Diagrammatic view of the left cerebral hemisphere, showing the four lobes, the two principal fissures, the cerebellum, and the medulla oblongata.

ward and upward, at an acute angle with the base of the brain (see Fig. 3).

There are on the outer lateral surface of each hemisphere four lobes or major divisions of the brain. These lobes are in turn subdivided by smaller fissures into various convolutions.

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The four lobes are placed as follows : The frontal lobe is that portion of the cortex of the front of the brain extending backward to the fissure of Rolando, and downward to the base of the brain and the fissure of Sylvius. The parietal lobe is that portion of the brain immediately behind Rolando, extending downward to Sylvius and backward to the parietooccipital fissure (marked P. O. F. in Fig. 3). The occipital

Fig. 4. — Showing the chief convolutions on the lobes of the lateral surface of the left hemisphere of the brain.

lobe extends from the parietal down to the base of the brain. The temporal lobe lies below Sylvius and extends backward to an ill-defined boundary between the parietal and the occipital lobes, and downward to the base of the brain.

Each of the lobes we have been considering is divided by fissures into more or less distinct convolutions. For instance, the frontal lobe is divided into the first, second, third, and ascending frontal convolutions. The position of the most important lateral convolutions may be seen by referring to Fig. 4.

The convolutions of the inner halves of the hemispheres are not so easily understood without a model. Figure 8, p. 18, shows as well as a diagram can the leading mesial convolutions.

Our next step is to determine what parts of the brain are exercised by the various sensory and motor stimuli of life. We can then attach some definite meaning to an undeveloped brain spot, — give it a local habitation and a name.

Localization of brain function has only recently been demonstrated. There is nothing surprising in the fact that different parts of the brain should have different functions. We might infer in advance that such would probably prove to be the case. Dr. Michael Foster says of the human body as it develops, "Some cells put on certain characters, and others other characters ; that is to say, the cells undergo histological differentiation. . . .

" This histological differentiation is accompanied by a physiological division of labour. . . . Instead of all the units as in the amoeba doing the same things equally well, the units of one tissue are told off as it were to do one thing especially well, or especially fully, and thus the whole labour of the body is divided among the several tissues." 1

One of the important functions of the brain is to send out automatic motor impulses. We decide to pick up a pen, to move a foot, to utter a word, and we voluntarily innervate a certain portion of the brain. If the nerves leading from this to the proper muscles are unimpaired, the motion follows. The motor functions of the brain are the most accurately localized of all.

The motor zone is that part of the brain adjacent to the

1 Foster's Text-book of Physiology, p. 6.

fissure of Rolando. If we were to take a monkey, and remove the skull over the fissure of Rolando for a short distance on both sides of it, we should expose the motor zone. We could prove this by exciting various portions of this tract with an electric current. If the brain at the extreme upper portion of Rolando was excited, the monkey's leg would be moved. If the current was confined to a certain small part of this area

Fig. 5. — Lateral surface of a monkey's brain, showing the motor centres. - Halleck's Psychology, from HORSLEY and Schafer.

(see Fig. 5), only a toe might be flexed. Repeated experiments were successful in mapping out a motor region so exact that such small centres as those concerned in moving a thumb or contracting the larynx have been located. While it is true that these areas were originally localized on the monkey's brain by stimulating different points with electricity, there is sufficient similarity between the human and the simian brain,

H to warrant locating the principal areas in corresponding places on the human brain. The chief fissures are the same in both brains. Of course, human beings cannot be directly experimented with in this way, but monkeys have been especially serviceable to human beings along this line.

A few years ago the boldest surgeon would have hesitated to cut into the brain, even when there were symptoms that some-

Line points to issure of Rolando

Fig. 6. — Diagram of motor localization in the human brain.

thing serious must be the matter with it. In the last decade of the nineteenth century a physician can write, " When I say that the existence of a tumour about the size of the end of the forefinger can be diagnosticated, and that before touching the head it should be said (and I was present when the statement was made) that it was a small tumour, that it did not lie on the surface of the brain, but a little underneath it, and that it lay partly under the centre for the face and partly under that for the arm in the left side of the brain, and that the man was operated on, and the tumour found exactly where it was believed to be, with perfect recovery of the patient, it is something which ten years ago would have been deemed the art of a magician rather than the cold precision of science." 1

In the case of an epileptic patient, it was noticed that a preliminary twitching always began in the left shoulder. The surgeons cut a circular hole through the right side of the skull immediately over the shoulder centre. Beneath the incision they found a small tumour, which they removed. A sewing-girl was subject to fits of epilepsy, and it was observed that the preliminary convulsive twitching always began in the right thumb. The surgeons cut through the skull directly over the motor centre for the hand. They then stimulated the brain cortex until they found a surface where the thumb alone was flexed. It was necessary to determine this point accurately, for if the brain beyond this was injured, the hand and entire arm would be paralyzed, and the poor sewing-girl could then no longer earn her living. The surgeons succeeded in removing the thumb centre alone, and, as a result of the operation, her epileptic attacks were fewer and milder in number. She also had the use of her hand.

The important motor centre for speech lies in the third left frontal convolution for right-handed people, and in the corresponding convolution on the right side of the brain in the case of those left-handed (see Fig. 6). When we wish to talk, we must innervate that portion of the brain. If a person understands what is said to him, but is unable to control his organs of speech so as to reply, he is said to be suffering from motor aphasia. Since the centre for hearing lies in a different part of the brain, the unfortunate may understand l Vivisection a?id Brain Surgery, by W. W. Keen, M.D.

everything that is said to him and yet be unable to utter a word in reply. If his hand centre is unimpaired, he may write answers to questions as well as ever. No one can be an intelligent student of memory if he does not know such facts as these.

We must now consider in what part of the brain the various nerves of the special senses discharge the stimulus which they

Fig. 7. — Side view of left hemisphere of human brain, showing the principal localized areas. — HALLECK'S Psychology.

bring. We shall find the sensory areas less definitely mapped out than the motor tracts. We have, however, evidence which shows that each sense has its headquarters in some special part or parts of the brain. We must, nevertheless, bear in mind that no part of the brain is absolutely restricted to either motor or sensory nerves. We name the tract from the predominance of the nerves which end there, just as we call Paris a 'French city, although there is also dwelling in it a sprinkling of people from other nations.

M THE CENTRAL NERVOUS SYSTEM 1 7

The centre for sight lies in the occipital lobes, both on their exterior and mesial surfaces, and it sometimes extends as far up as the end of the fissure of Sylvius (see Fig. 7). When the cortex has been peeled off this part of a monkey's brain, the animal is blind. Injuries to this part of the human brain have resulted in more or less complete loss of sight. Investigations in this field have enabled us to distinguish between psychic and sensorial blindness. Psychic blindness is lack of recognition of an object that is actually seen. Thus, when the brain of a frog- or a pigeon is removed, the animal may still see objects and avoid them when it moves. But the fact that such a pigeon has no fear of a cat or any other object shows that psychic blindness exists. Objects are seen, but not recognized. Sensorial blindness exists when no sensation from light is experienced. A Scotchman met with an accident that brought on him psychic blindness. He saw physically as well as ever, but he could not interpret what he saw. He would look at the most familiar objects and be utterly unable to recognize them. He would gaze at his New Testament without knowing what the object was until he ran his hand over the smooth cover, when he immediately recognized it. When a piece of detached bone, pressing on the centre for vision in his brain, was removed, he recovered his power of mentally interpreting what he saw.