Brain and personality, or, The physical relations of the brain to the mind

Front matter

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Contents

CHAPTER PAG*

I Historical Introduction . . 1

II Account of the Physical Basis of

Chapter I

There is no more interesting subject in science than the physical conditions under which we become thinking beings. Though science is concerned with the knowledge which comes from investigation and experiment in the physical world, yet she cannot evade being questioned about the relations of matter to mind, because the bodily organ of the mind is a thing of physics. Hence however discussion about mind may be waived as pertaining to the province of metaphysics this cannot be done with that collection of matter which is called the brain. In it mind and matter come together, and therefore we cannot help asking liow ranch the one is dependent upon the other.

As far as the mind is concerned, it must be admitted that no study of its own operations can give the least inkling on this question, any more than a study of the words of a telegram would reveal how a wire came to conduct them. The passage of thought in the one case and of words in the other are equally invisible. But the wire can be followed up until it connects with a mechanism which generates the words for the wire to transmit. Can any analogous result be expected from an examination of the physical mechanism through which the mind acts?

The answer is that something of the kind seems to be assured by modern discoveries of definite relations between particular portions of brain matter and thought. That there are certain material seats of purely mental functions in the brain is now demontrated beyond mistake by the fact that when these are physically disorganized their special mental functions are forthwith abolished, though all other places in the brain remain intact.

It is significant, however, that these discoveries relate in the first instance to the working of the brain of Man in distinction from the brains of animals. Restricted to the brains of animals which they could experiment with, physiologists would have been but little able to determine what special relations the brain held to thought. But with the brain of man it has proved to be wholly different, because, unlike animals, man possesses a faculty which is directly related to thought, the great faculty of speech, and the specific anatomical seats of speech have been found in the human brain as certainly as the ticker is found in its place in a telegraph office.

It should be remarked, however, that it was reserved for physicians and not for psychologists to light upon these great discoveries by their observing what may be termed the effects of experiments with the human brain which disease makes for them.

While it has been a distinct gain for psychologists to leave metaphysics and turn their attention to the general physiology of the nervous system, the criticism may be made that apart from the human brain the field of psychology is very limited as far as the relation of mind to matter is concerned. A single very circumscribed injury to a place in the human brain may teach more on this subject than a survey of the whole domain of nervous physiology in animals. This is well illustrated by the fact that the identification of speech centers in the brain ere long led to the discovery, again by medical men, of the material seats of a whole series of other faculties both sensory and intellectual; so that taken together these findings give to the subject of the physical relations of the brain to the mind an entirely new aspect.

These discoveries, however, have all been made within the lifetime of our own generation. On that account they are scarcely known to the general public, and their important bearing on the old question of matter and mind is even less appreciated. Few persons are aware how slow the progress of knowledge has been of the actual physical relations of the mind to the body, and hence an historical review of that progress would seem to be a fitting introduction to our present discussion.

Thus the word brain does not once occur in the Bible, for the good reason that during the centuries in which its different books were written scarcely any one in the world suspected that this most silent and secluded of organs had anything to do with thought or feeling. With the Hebrews, the heart was the chief seat of the soul, while the mind was located in the kidneys, and all tender emotions in the bowels. Thus, one psalmist says that “ His reins [kidneys] instruct him in the night seasons and another that “ The Lord trieth the heart and the kidneys.’ *

The prophet Jeremiah denounces the hypocrites of his day, who “ had the Lord in their mouths, but not in their kidneys.” In keeping with similar expressions in the Old Testament St. Paul speaks of “ bowels of mercies.” A survival of these conceptions is found in our English phrase, “ Two fellows of the same kidney.”

Nor for a long time were the ideas of the Greeks on this subject much nearer the mark. It is true that Plato assigns the supreme seat of the mind to the brain, but how purely speculative were his views is illustrated by the following quotation :

“The creation of bones and flesh was in this wise.

“ The foundation of these is the marrow which binds together body and soul, and the marrow is made out of such of the primary triangles as are adapted by their perfection to produce all the four elements. These God took and mingled them in due proportion, making as many kinds of marrow as there were to be hereafter kinds of souls. The receptacle of the divine soul He made round, and called that portion of the marrow brain, intending that the vessel containing this substance should be the head. The bones were formed by sifting pure earth and wetting it with marrow. It was then thrust alternately into fire and water, and thus rendered insoluble by either. As the bone was brittle and liable to mortify and destroy the marrow by too great rigidity, He contrived sinews and flesh, the first to give plasticity, the second to guard against heat and cold. Having this in view, the Creator mingled earth with water, and mixed with them a ferment with acid and salt, so as to form pulpy flesh, etc.” 1 It is evident that Plato in this confounded the substance of the brain and of the spinal cord with the marrow of the bones, and thus got his conception of marrow as the foundation of the living body. But his younger contemporary, Aristotle, circ. B.C. 335, who was

1 Jowett’s Translation, vol. iii., pp. 339 sq. 362.

the foremost physiologist of his day, and himself the son of a physician, scouted all this vital farrago of Plato’s, and as Plato evolved it all out of his own head, without troubling himself about facts, he had little difficulty in doing so. Aristotle examined the brain for himself, and came to the conclusion that its function had nothing to do with mind, but that it was a cool organ which properly refrigerated the blood for the heart !

We may be tempted to smile now at this conclusion, but Aristotle was no mere theorist, and he reasoned according to a sound scientific method from facts as he knew them. We must put ourselves in his place, with nothing to go by more than certain patent facts of life, the explanation of which by other facts was then unknown to him. He found the brain an apparently insensible and inexcitable organ, while the heart was extremely excitable. He therefore only followed his great predecessor Hippocrates, the Father of Medicine, who, recognizing liow quickly consciousness is abolished by loss of blood, or deranged by blood poisons, or by the heated blood of fevers, inferred that the conscious mind resided in the blood, and hence that the heart, as the central organ of the circulation, was itself the chief seat of the soul.

Another cause of misunderstanding was that, as the arteries are found empty after death, owing to their contractile walls expelling the blood from them, it was concluded that these vessels carried air or ethereal spirits from the heart to the rest of the body. We shall see that nothing so contributed to delay for centuries all progress as this mistake, by its suggesting the existence and all-pervading power of vital spirits.

Supported by such great names as Hippocrates and Aristotle, these beliefs held sway for fully five centuries, along with speculations how from the blood the different organs of the body, such as the stomach, liver, spleen, intestines, etc., elaborated each its share of the various appetites or emotions.

Meanwhile, in this wilderness of Greek speculation, a voice had been crying in vain the true doctrine about the brain long before Plato or any of the rest. Alcmaeon, the Pythagorean of Crotona, who lived about B.C. 500, a man who was both an anatomist and an experimental physiologist, taught that the brain was the sole seat of the mind and the source of feeling and of movement, and that at the brain arrived all sensation by means of the nerves. It is evident that he was led to do this by noting that severing the optic nerves leading from the eyes to the brain produced total blindness. Unfortunately he called the nerves tendons, a term which, with its erroneous suggestions, continued to be applied to them for two thousand years, until finally the great Descartes demonstrated the essential difference between tendons and nerves. (Even Shakespeare when he spoke of nerves meant sinews.)

But whether from Alcmaeon’s colonial origin, or because he was far in advance of jhig time, both Plato and Aristotle, who must have read his works, alluded to them contemptuously as “ somebody’s ” views. Aristotle, indeed, taught that the spinal cord had nothing in common with the brain, and evidently paid little attention to its “tendons ” or nerves.

In progress of time a great school of anatomists and experimental physiologists arose in Alexandria, of whom Herophilus, circ. B.C. 300, and his contemporary, Erastistratus, were the chief, who carefully dissected the brain and traced to it the nerves of the special senses, as Alcmaeon had done. They went so far as to divide the nerves into those of sensation and of motion, though they were still hampered by Alcmaeon’s term “ tendon,” and apparently they could not wholly shake off the authority of Aristotle as to the functions of the brain.

They prepared the way, however, for Gall len, circ. A.D. 160, to whom we are chiefly indebted for the overthrow of Aristotle’s doctrine about the brain, and the demonstration of its exclusive title as the seat of thought and feeling. To this great physician belongs the distinction of establishing this doctrine for all time. A contemporary of his, Aretaeus of Cappadocia, circ. A.D. 170, advanced so far as to recognize correctly that the brain dominated the muscular movements of the body by nerves, which, originating in the brain, crossed their tracts below in the form of the letter X, so that injuries in one hemisphere of the brain paralyzed the muscles of the opposite side of the body, while if they occurred in the spinal cord below the medulla, the resulting paralysis was on the same side with the injury. But even Aretacus held that the seat of the soul was in the heart.

After Galen the progress of discovery of the true functions of the brain was extraordinarily slow. From the middle of the second century A.D. to the middle of the nineteenth century, or 1,700 years, the actual gains in this knowledge were relatively most insignificant compared with the splendid advances in astronomy, geography, physical science, chemistry and geology. It would seem as if “to know thyself 99 scientifically rather than metaphysically, instead of being the first was destined to be among the latest of human achievements.

One great cause for this backwardness was the persistent sway of teleology in all questions about life. Men were ever trying to explain the reasons of things by the imagined purposes of things, and to find the causes in the purposes. Thus we have seen that Plato’s whole physiology originated in what he fancied the Creator and the gods intended when they made this or that part of the living body. And all the long way down the centuries we meet with examples of reasoning on these subjects not unlike that of the philosopher who admired the benevolent wisdom of Providence in arranging that large rivers should flow past large towns.

One of the greatest of these hindrances was the conception of the brain as a secreting gland, which dates from Hippocrates and continues down to Karl Vogt, Cabanis, and other writers in the earlier years of the nineteenth century, who maintained that the brain secreted thought just as the liver secretes bile. Hippocrates writes that: “ The brain resembles a gland, being white and soft like glands. It discharges the same glandular offices as regards the head. It rids the head of its humidity, and returns to the extremities the surplus of its flux. ’ ’ With this postulate, that it is a gland, one authority after another attempted to represent the brain’s secretion as a kind of subtle fluid termed “animal spirits,” which permeated the body through the blood. Thus Descartes taught that the left ventricle of the heart separated these animal spirits, which had been generated in the brain, and distilled them out of the blood into a “ very living and very pure flame,” and then distributed them through the arteries. These animal spirits, therefore, were readily made to account for everything, normal and abnormal. Hence, it was due to noxious vapors and humors that every variety of bodily disorder took its rise.

To illustrate how effectually such conceptions served to block all progress in the science of life we may quote one instance from a ponderous volume in my library with the date 1618, on “Physiology and Anatomy,” by Hilkiah Crooke, Physician and Professor on Anatomy and Chirurgery to His Majesty, James I.

Speaking of the origin and growth of hair, he says : ‘ 1 The immediate matter of the haires is a sooty, thicke, and earthy vapour, which in the time of the third concoction [distillation] is elevated by the strength of the action of naturall heate, and passeth through the pores of the skin, which heate exiceatetli or drieth this moysture of these sootie and tliicke vapours, for the vapour being thicke, in his passage leaveth some part if it selfe, to wit, the grossest, in the very outlet, where it is impacted by a succeeding vapour arising where the former did, is protruded and thrust forward, so that they are wrought together in one body. The straightness of the passages of the skin where through the matter of the haires is auoyded, formetli them into a small roundness, even as a wyre receyeth that proportion whereof the whole is, where through it is drawne.”

One great office of the hairs of the head, therefore, Crooke perceived to be to lead otf “ the vapours which otherwise would choke and make smoaky the braine,” though how hopelessly choked the brains of all bald heads hence would be he does not mention. Crooke ’s illustrious contemporary, Lord Bacon, held that the blood did not distend the heart, nor cause it to beat, but that was done by its contained spirits. Even Harvey’s discovery of the circulation of the blood did not dislodge these pure nonentities from the brain, for we find as late as 1824, Dr. J. Mason Good, in his “ Study of Medicine,” mentioning the fact that the brain being a gland, the nervous power or energy issues from it as a fluid of a peculiar kind, and is so distributed by its nerves.

It was the introduction of the microscope into the investigation of nervous tissues which first really exorcised the “ animal spirits ” from the medical world. Their objective existence in fact had often been called in question before, but it was difficult to banish these airy creations altogether until some solid physical facts could be found which would dispose of them.

Without the microscope we could never have known what every living texture really is, nor after what fashion it is constructed. With the microscope Ehrenberg made in 1833

the first discovery of a nerve cell in a spinal ganglion, and four years later Purkinje demonstrated that the gray matter of the cerebrum and of the cerebellum is made up of nervous cells and their fibers. This was followed in the next year by the publication of the great work of Schleiden and Schwann, in which they proved that all vegetable and animal tissues are made up of cells and the products of cells. The intimate structure of all tissues and organs was thus revealed, and each was found to be perfectly characteristic of its kind, whether bony, tendinous, glandular, muscular, nervous, etc. Nervous tissue especially is very peculiar and unlike anything else in the body, and least of all like glandular tissue. The brain, therefore, was thus shown to be no more a gland than a hand or foot is, and that it never secretes anything. The brain instead is a special and distinct organ, connecting with nothing but nerves, acting and acted upon only through nerves or nervous masses, called ganglia, which are distributed through the body.

It was not long before this conception of the brain as a separate mechanism in us, constructed after its own pattern, began to give rise to a new batch of theories. Gall — to whom brain anatomy owes a good deal, particularly in the tracing of the course of the brain fibers down through the medulla oblongata— regarding the brain as one organ, conceived that its convolutions served to mark it off into so many compartments, each with its distinctive mental functions which he proceeded to identify. He thus made out a list of twenty-four brain localities possessed with special intellectual or moral attributes, and which his pupil Spurzheim increased to thirty-eight. Now as all individuals have their personal peculiarities of mind and of disposition, these, in turn, could be explained by the development of their corresponding convolutions. Thus, a mathematician would liave a highly developed mathematical convolution, and a combative man would possess his brain seat of combativeness, etc. This so-called science of phrenology had great vogue for a time, owing to its further assumption that the outer contour of the head corresponded to the arrangements of the convolutions within, and thus afforded a ready physical basis for estimating what manner of man or woman each person was. So popular became this supposed scientific standard of individuality, that I once heard a prominent clergyman remark that before he addressed a young man about his soul he wished he could be allowed to feel his “ bumps.”

But as in the case of animal spirits, so phrenology had to disappear before facts. It was shown that Gall and his followers did not study a sufficient number of brains, because, on the one hand, their mathematical convolutions were found as largely developed in the brains of paupers, dying in hospitals, as in the few mathematicians whose brains Gall had investigated ; while the brains of some eminent men had no specially developed convolutions where they ought to have had them.

On the other hand, while the inner table of the skull corresponds in a general way with the subjacent convolutions, it does not keep shape with any special convolution whatever ; while as respects the outer table of the skull there may be no correspondence at all. Phrenology, therefore, gradually became the exclusive property of popular lecturers, who illustrated its doctrines with plates of variously labeled heads.

The period between 1845 and 1860 was marked by notable advances, not only in general physiology, but also in the physiology of the brain and of the nervous system. The great principle of reflex action, that is, of the afferent and efferent elements in all nervous processes, was established, and many of the amazingly intricate paths of nerve fibers in the spinal cord and in the brain were traced out. France at that time took the lead in all branches of medical science, and the names of Majendie, Longet, Flourens, Gratiolet, and others like them will always rank high in the annals of neurology. It is not easy at this day to appreciate what a paramount influence was exerted in the medical world by this school of Paris, whose lecture rooms were crowded by students from all countries.

But, partly as a reaction from the doctrines of phrenology, all separate localization of functions in the brain was strongly denied, while the opposite and no less erroneous teaching was promulgated, that the brain always acts as a whole. The cerebral convolutions were regarded as the “ sensorium commune,” and, as one of them expressed it, “ any specific vibration initiated in each kind of sensory nerve thrills throughout the whole or greater part of the mass of the brain.’ ’ Thus medical opinion seemed to settle down to the conclusion that our two brain hemispheres corresponded to our two lungs, in the respect that every part discharges the same functions with the rest.

But a great change was impending. On April 14, 1861, an eminent French hospital surgeon, Paul Broca, read a paper before the Societe d’Antliropologie of Paris, in which he adduced evidences to prove:

That there is a definite locality in the brain which is the sole seat of articulate speech, found in a limited area in the lower and posterior part of the convolution called the third frontal and which is now named “ Broca’s convolution.” This fact, of course, could only be demonstrated by injuries to that part in the human subject, and Broca showed, by citing a number of post-mortem examinations of persons dying after paralysis of the right side of the body, usually due to apoplexy and who with the onset of the paralysis lost the power of utterance — that in all such cases damage to that locality was demonstrable. As this statement seemed at first to be a reversion to the tenets of phrenology, it gave rise to so much heated discussion and denial, that it was not until about 1865 that it began to be generally admitted.

What chiefly led to its final acceptance was the further discovery that the two other elements of human speech besides articulate utterance also have each their distinct and separate brain localities; one place being found for the words we receive through the ear, damage to which place causes ivord- deafness, even though there be no deafness to other sounds than words ; and, secondly, one place for words received through the eye in reading, damage to which causes the subject at once to become wholly illiterate, though he may see and recognize all other objects of sight, except words, as well as ever.

The demonstration of these anatomical bases of the faculty of speech soon led to careful experimental investigation of the brain in animals for other seats of distinct functions, constituting what is now termed cerebral localization, and to a comparison of the results achieved with the effects of injury or of disease in the brain of man. By 1870, through the labors of both experimental physiologists and practicing physicians, such as Hitzig,

Ferrier, Munk, Luciani, Charcot and others, it was shown that each of the special senses has its anatomical seat in the brain; and, in addition to that, in a centrally placed zone are to be found the seats governing the voluntary movements of the muscles of the body, so that each muscle, or group of muscles, can be made to contract by excitation of the corresponding locality in the cortex or surface of the brain.

These discoveries were great enough of themselves, but they are relatively of secondary importance compared with those which followed and which will cause the name of Broca, as yet scarcely known by the general public, to rank in the history of science along with the names of Copernicus and of Isaac Newton. The anatomical seats of the senses, and those of muscular movements, are found equally in both hemispheres of the brain, and their functions, as such, are doubtless congenital. It was thus natural to infer, as the brain is a double organ, like our two eyes and our two ears, each hemisphere being the duplicate of the other, that both brains would equally participate in all brain work.

But a most unexpected fact, and one of far-reaching significance, was soon demonstrated, namely, that the anatomical seats of the faculty of speech are found only in one of the two hemispheres. Thus, if the Broca convolution, which is the seat of articulate speech, be damaged in a person after middle life, the loss is usually irremediable, so that he can speak no longer though the same convolution in the other hemisphere be wholly intact. The same is true as regards word-deafness or word-blindness from injury of their respective places, for the corresponding localities in the other hemisphere, though not hurt at all, nevertheless are entirely word-deaf and word-blind, simply because they never had anything to do with speech.

But here again another new element in the problem presented itself, which proved that the endowment of one hemisphere with the great gift of speech was not owing to any original or special fitness of that hemisphere for such a function, but solely because it was the hemisphere related to the most used hand in childhood. In all right-handed persons, it is in the left brain that the speech centers are located ; while in left-handed persons, they are found exclusively in the right brain.

Two conclusions inevitably follow upon these facts, first, that brain matter, as such, does not originate speech, for then both hemispheres would have their speech centers ; and second, that either of the hemispheres is equally good for speech, if something begins early enough in life to use it for that purpose. That something is the most commonly used hand by the human child at the time when it is learning everything, for self-education always begins in our race with the stretching forth of the hand, as any one may note in the first purposive actions of an infant. The hand which it then most used to learn by determined which of its two brain hemispheres should know speech, and which hemisphere should remain wordless, and therefore thoughtless, for life.

This latter statement, that thought, as such, is a function only of the hemisphere connected with the faculty of speech, was decisively demonstrated by the next revelation which followed upon Broca’s fruitful discovery. Without any help from metaphysics, and upon a much surer basis than any metaphysical theories, it was simply found as a physical fact that our mental faculties, as such, are quite distinct from the elementary functions of sensation and of motion. These latter are congenital, but our ability to recognize and, therefore, to know what the particular objects or meanings be of what our senses report, is not congenital, but as much acquired by us as our speech is acquired and not congenital. Because, connected with the original anatomical seats of sight and of hearing were found certain physical, anatomical areas of brain matter, injury of which abolished all power to recognize what the eye sees or the ear hears. In the visual area is a place which, if damaged, renders the person unable to recognize members of his own family, though he see them; and in the auditory area are places, one of which, if hurt, causes the person to be no longer able to know his most familiar tunes when he hears them; while, by injury in another spot, he loses all power of distinguishing sounds in general, so that he cannot tell the bark of a dog from the song of a bird, because they are alike only noises to him. And here again, these important brain areas in us, interpreting what sights or sounds mean, are found only in the left hemisphere of the right-handed, and in the right hemisphere of the left-handed; in other words, in the hemisphere in which the seats of the faculty of speech are located.

The decisive bearing of these pure matters of fact upon our whole discussion of the Physical Relations of the Brain to the Mind and to the Personality is plain enough. As none of these wonderful mental faculties, including that of speech, were connected with brain matter at birth, but were created afterwards, it follows that they were created by the individual himself anatomically modifying his own brain. That brain matter did not itself organize these physical areas of mental function is shown by their entire absence from the convolutions of the wordless hemisphere.

As these physical relations of the brain to the mind are to be fully discussed in our succeeding chapters, we would have preferred not to have alluded to them so far in advance, and we have done so now only for this reason. Many persons may imagine that such a theme must involve a discussion of what the mind is, and, therefore, enter upon the wide domain of metaphysics. We propose to avoid anything of the kind, as our subject deals primarily with a thing of physics, namely, the brain. But the main facts about the structure and working of the brain are of such recent discovery that they scarcely yet have become generally known, at least in comparison with the latest discoveries in the physical sciences. Regarded, however, simply as matters of knowledge, these new additions to our information about the one organ in us which is related to thought can be second to none in interest and importance.