Popular Science Monthly/Volume 26/November 1884/The Relations Between the Mind and the Nervous System
THE
POPULAR SCIENCE
MONTHLY.
NOVEMBER, 1884.
| THE RELATIONS BETWEEN THE MIND AND THE NERVOUS SYSTEM.[1] |
By WILLIAM A. HAMMOND, M. D.
IN order that one person may know what another person is talking about, there must be an agreement in regard to the meaning of the terms employed. Without this there can be no common ground on which those engaged in a discussion as speakers and listeners can stand. For it is obvious that if by a word one of the disputants means one thing and another by the same word means quite another thing, they will both talk of different things, and that hence their statements and arguments will be worse than useless, for they will not only have been of no avail in convincing an adversary or in instructing a pupil, but they will in all probability have been potent agencies in stirring up the bad blood that so often shows itself where, least of all, it ought to appear—in efforts to arrive at the truth.
It is especially necessary that there should be no misunderstanding in regard to one's terminology when we come to discuss those subjects in regard to which our knowledge is not full and precise, and which, consequently, have been studied from different stand-points by different inquirers, and by the light that their own minds have thrown upon them rather than by that of other minds. Suppose, for instance, that a doctor of music should go into the turpentine-regions of North Carolina to give a lecture on "pitch" to the dwellers in the pine-forests, and should talk of the elevation of the voice or of an instrument—is it not quite within the range of probability that some one of the audience would rise in indignation and tell the learned gentleman that he did not know what he was talking about, and that every man, woman, and child in the State knew that pitch was a "thick, black, sticky substance obtained by boiling down tar," and not only that, but he and the greater part of those present would feel as though their attendance had been obtained by false pretenses, and that the money they had paid for admission should be returned to them?
Or, if I should go out among the sturdy farmers of Northampton County and gather them together to hear a lecture on "ducks," and should confine my remarks to pets and darlings of the female part of the human species, is it not very certain that though the young agriculturists in search of wives would listen with eagerness to what I had to say (and it would be interesting, I think), the more sedate would feel as though I had played them a trick? Neither the young nor the old would have got what they came for, and yet there would be ample authority for the meaning given to the word.
And when I come before an educated assemblage such as this, composed to a great extent of persons of both sexes, who have been in the habit of thinking deeply on subjects of vast importance, and who have formed clear ideas of what meanings are to be given to the words they meet in their studies or use in their conversation, it is indispensable that if I wish to make myself understood and to speak with that force so essential in obtaining assent, I should do all in my power to avoid ambiguity of signification.
It would be very easy to bring before you many subjects in regard to which you have your own ideas, formed after much study and reflection, and to which, therefore, you would have a right to cling, and I should be obliged to start out by attempting to define accurately the terms to be employed. I doubt, however, if it would be possible to select one in which such a course would be more necessary than in that of which I am to speak to-day. The word "mind" is a little one, but it means a great deal, and if we strive for accuracy, as of course we should do, it means a great many different things. In fact, it is probable that, were I to send a canvasser among you, I should receive a hundred different explanations of the term, and nowhere would the variations be more numerous or more transcendental than among the eminent gentlemen—president, professors, and trustees—who constitute the governing body of this university; for I think I have observed that, the higher we go in mental development, the more numerous and refined are the differences as to what the mind is. No two metaphysicians ever yet exactly agreed in regard to the signification to be attached to the word mind.
But, before explaining to you my understanding of the term, it is necessary, in order to avoid all ground for misconception, to tell you what I do not mean. I do not mean the soul, although it and the mind are by a large and influential class of philosophers regarded as constituting one essence—as being, in fact, identical. With it, however, I conceive that we have nothing to do, so far as science goes. Its very existence is a matter of faith in which, probably, most of us believe, but which is altogether beyond the limits of proof, or even of investigation. There is nothing tangible about it. We should not know how to proceed to ascertain the existence of the soul. No one could go into a court of justice and demonstrate by the rules of evidence that he himself, or his neighbor, has, as an integral part of his organization, a never-dying principle responsible to God for the deeds done in the body. He could not say that life is the soul, for, if he did, he would have to accord souls to all living beings, vegetables as well as animals. And, if he were to declare that the mind and the soul are identical, he would be obliged to admit that the "beasts that perish," and even the vine that creeps up the side of his house and finds out where the supports are situated around which it sends out its tendrils, have souls which, if not as perfect as his own, are none the less real. No, his belief in the existence of his soul rests upon higher principles than those that govern earthly tribunals or scientific investigation. He believes through the faith that is in him, not through the impressions that have reached his central nervous organs through his eyes or ears or nostrils or tongue or fingers—the only mediums by which actual knowledge can be obtained.
But with the mind it is very different. Its existence, its powers, its aberrations, are proved in courts every day, and we are constantly demonstrating its reality in our physiological and pathological laboratories, and in our hospitals and in the practice of our physicians. In fact, it is being shown every instant, in the person of every man, woman, and child, and in every living being throughout the earth, that mind exists and is a power. We see it exhibited in all its varieties. We are all of us familiar with good and bad minds, and some of us see human beings with minds so degraded and undeveloped that they are lower, so far as regards intelligence, than dogs or canary-birds. They do not know enough to reach out their hands and take the food that is placed before them, whereas we have all seen canary-birds haul up with their beaks whenever they were hungry the little wagons of seed on the outside of their cages.
But, though the minds of these poor beings are many of them inferior to those of our domestic animals, it would be presumption in us to say that the soul of the veriest idiot that breathes is not as pure and as high in the scale of souls as that of a Plato or a Newton, If the mind and the soul are identical, all those predisposing causes inherent in the parents, and which are capable of causing imbecility and idiocy in the offspring, are also capable of damaging the immortal soul that we believe God has given to every human being. The little piece of bone of a fractured skull that, pressing upon the brain, stupefies the mind, at the same time damages the soul; the congestion or inflammation of the brain that converts a man of giant intellect into a maniac or a dement beyond the hope of cure, also irreparably ruins the soul, which, we are told, never dies, and which, if it exists, is doubtless far removed from the influence of bodily diseases or injuries. Therefore I beg you to understand that what I have to say relates solely to the mind. Your souls are, doubtless, cared for by those whose qualifications for instructing you in their management are greater than any that I can claim.
Now, what is mind? Those of you who have thought much upon the subject will not be surprised when I say that I do not know. There may be others, however, who, though too polite to say so, may think it a piece of impertinence for me to come here to speak of something of the nature of which I am obliged at the very beginning of my discourse to confess my ignorance. But, if they thought thus, they would be doing me great injustice, and it would be easy for me to retaliate by asking them what a piece of wood is. Could they tell? Does any one know? Does any one know what anything is? There are sixty-four elementary bodies of which the earth is composed, but does any one know what a single one of them is? Take one with which you may be presumed to be especially familiar—iron. What is it? You do not know. You can describe it to me. You can point out its properties. You can tell me where it comes from. Yes, and I can do the same with the mind. I can tell you where it comes from, describe its properties, point out its manifestations, and you will recognize mind as clearly as I should recognize the iron, the qualities of which you should portray; but, as to telling you what mind is, I can not do it any more than you can tell me what iron is.
Some of you are students of physics. If you were to present yourselves in the class-room and ask your distinguished professor of that branch of science to tell you what heat, light, electricity, magnetism are, he would be obliged to tell you that he does not know, just as I am forced to tell you that I do not know what mind is. But, though he is ignorant of their essential natures, think of the vast fields of knowledge he is able to open up to you by putting you in possession of what is known of these forces!
Go into the chemical laboratory of your own noble university—in honor of whose founder we are here to-day—and touch the two poles of a galvanic battery. What is it that thrills through your bodies, and perhaps even burns the skin of your fingers; or, even, if the current be strong enough, strikes you dead on the instant? Galvanism. What is galvanism? A force. Yes, and so is light a force, and heat, and gravitation. But, when I am told this, I am just as far from knowing what any one of the forces is as I was before. All that you could do, if I persisted in asking for a fuller explanation, would be to tell me something of the origin and properties of the force in question, and in this way I should obtain some idea of its characteristics, and should be in no danger of mistaking it for any other force. That is what your Professor of Physics does for you. and, if you have only profited by the instruction you have received, you have a store of facts at your command that will enable you to recognize heat, light, electricity, gravitation, magnetism, whenever you see them manifested. When, therefore, you ask me what mind is, I answer that it is a force possessing peculiar properties, and developed by a substance constituting a part of the nervous organism of man and other animals, and known to anatomists and physiologists as gray nerve-tissue. This is similar in all essential respects, so far as its terms are concerned, to the definition that you would give me of any other force. Of course, it can be made more precise and extensive, but no enlargement would change its character.
The gray nerve-tissue exists in the form of aggregations of minute cells in various parts of the nervous system. In man, by far the largest collections are found in the brain, and especially on the outside of it, covering it as the rind covers an orange, and hence called the cortex, or the cortical substance. Besides this large mass, spread out to the thickness of the twelfth of an inch or more over the exterior of the brain, there are masses of gray nerve-tissue in other parts, varying in size from that of a walnut to that of a small pea. In this diagram the situations of the masses of gray tissue existing in the brain are shown. You will observe a very beautiful arrangement for increasing the extent of the cortical substance without at the same time increasing the size of the brain, and thus making it heavier than it would be comfortable to carry. The surface is convoluted, and the gray matter, following the convolutions, is hence doubled over and over again on itself. If the cortex were spread out smoothly, like the skin on an apple, it would cover a body more than four times the size of the average human brain. We should, then, in order to get as much mind-producing substance as we have now, require heads four times the volume of those that we now carry on our shoulders. Gray nerve-tissue is found also in the spinal cord, and some animals, as the frog and the alligator, have more of it in this organ than they have in the brain. It also exists in connection with what is called the sympathetic nerve, in the form of masses called ganglia, and generally placed in intimate relation with the several vital organs of the body—as the heart, stomach, lungs, liver, etc.
Besides the gray nerve-tissue, there is another kind of nerve-substance called the white, and which, instead of consisting of granular forms or cells, is made up of tubes or fibers. The white nerve-substance has nothing to do with the evolution of nerve-force or mind. Its office is to transmit the nerve-force from the places where it is formed to other parts of the body. The great mass of the brain and of the spinal cord, and the whole of the nerves that ramify through the body, consist of white nerve-tissue. You will understand, therefore, that this substance is analogous to the wires of the telegraph, while the gray substance corresponds to the batteries. And just as a particular arrangement, for instance, of zinc and carbon and sulphuric acid, leads to the evolution of galvanism, so a particular arrangement of nerve-cells leads to the evolution of the force that we call mind. We can not explain why or how the galvanism comes from the zinc, carbon, and sulphuric acid; neither can we tell why or how mind comes from the nerve-cells. Both are ultimate facts beyond which we can not go, and may never be enabled to go.
Now, as by their properties we recognize any of the other forces of Nature that I have mentioned, so by its properties we recognize mind. An object is perceived, and it is the mind that perceives it; an idea is formed, and it is the mind that forms it; an emotion is felt, and it is the mind that feels it; an act is willed, and it is the mind that wills it. Hence, there are these four groups of mental faculties, to one of which every possible manifestation of mind belongs—perception, intellect, emotion, and will.
The many interesting points concerned with these categories of mental faculties do not come within the scope of the present remarks, the chief object of which is to discuss the subject of the relations existing between the mind and the nervous system.
In the very earliest times of which we have any record, and even at the present day among barbarous nations, the idea existed that the brain was not the only organ concerned in the production of mind. Thus, the emotions were, many of them, supposed to have their seat in the heart, the liver, the spleen, the bowels. Love, for instance, was conceived by the heart, as were also several other tender or compassionate feelings. The liver was supposed to be intimately connected with the depressing emotions, the spleen with spite or revenge, and the bowels with pity. So strongly was this idea implanted, and so universally did it prevail, that it has influenced the forms of speech among all nations that are not so low in the scale as not to have emotions. Thus we say that a person has "a good heart," the lover tells his lady-love that he "loves her with all his heart," and the sinner when he turns away from his wickedness is said to have undergone a "change of heart." The influence ascribed to the liver is shown by our expressions "melancholic," "choleric," and by one that I heard used a short time since by a man who was complaining of an insult that had been put upon him, and who said that it made "his bile flow." Then we say of a disagreeable or quarrelsome person that he is "splenetic," or that he "vents his spleen," and we speak of a pitiless person by asserting that he has "no bowels of compassion."
How could the notions that gave birth to such expressions arise in the human mind? Doubtless, the origin was due to the fact that, under the influence of certain emotions, there are disturbances in the organs with which they are associated. Thus, the passion of love produces a sensation of fullness in the region of the heart, and the action of the organ is quickened. In mental depression, or as a consequence of fits of anger, the liver is so deranged that the bile ceases to be produced, and pain is felt in that part of the body in which the liver is situated; and, when the emotion of pity is strongly experienced, a sensation of weakness, or, as it is sometimes called, a sinking feeling, is felt at the pit of the stomach.
It has been customary with modern writers—and I have until quite recently been of the like opinion—to regard these disturbances as being the effects of emotions that originated in the brain, and not as indicating that the organs in which they are felt have anything to do with the evolution of love or anger or fear or compassion, or any other passion or feeling. The idea has become so widely spread among educated persons that the brain is the only organ of the body that has any direct relation as a generator with the mind, that it seems like a tremendous blow at the system of existing facts to attempt to take from it any of its power. But it is only recently that physiologists and pathologists are beginning to make a thorough investigation into that great division of the nervous system consisting of the sympathetic nerves and their ganglia. If you will lock at this diagram, you will obtain some idea of the situation and connections of these nerves. As you see, they are situated on each side of the spine, and are in direct connection with the brain, and their ramifications extend to every one of the vital organs situated in the chest, the abdomen, and the pelvis. These nerves differ from the other nerves—those that convey impulses to and from the brain—in the remarkable fact that they have at various parts of their course little swellings or enlargements called ganglia, and which consist of gray matter. Now, gray nerve-tissue, wherever it exists, is a generator of nerve-force, or mind, and it is not unreasonable to suppose, therefore, that these masses of the tissue in question, that are placed around the heart, the liver, the spine, and other organs, and in vast number in their substance, have some influence in causing the production of those emotions that make themselves felt in the parts of the body with which former universal beliefs and our present forms of speech have associated them. We find, too, as an additional fact in support of this view, that in certain mental affections, characterized by great emotional disturbances, these ganglia are in various parts of the body the seats of disease.
Therefore, there is some reason for the opinion that not to the brain alone do we owe the evolution of mind, but that the sympathetic system of nerves is also concerned in its production.
But there is another part of the nervous system not generally regarded as a mind-producing organ, but which I am very sure is directly concerned in the evolution of the force which so pre-eminently by its presence distinguishes organic from inorganic bodies, and that is the spinal cord.
The spinal cord is contained in the vertebral column, or, as it is popularly called, the backbone. It extends from the brain to near the end of the trunk, and is at its thickest portion about the diameter of the end of the little finger. It contains throughout its whole length gray nerve-tissue arranged somewhat in the form of the letter H. The diagram to which I direct your attention shows the arrangement on a greatly magnified scale. More than nine years ago, in an address delivered before the New York Neurological Society, and entitled "The Brain not the Sole Organ of the Mind," I called attention to the fact that certain mental faculties are seated in the spinal cord. It will probably not be out of place if I adduce here some of the facts and arguments upon which I based that opinion, and which convince me of its correctness.
As we have just seen, all the manifestations of which the mind is capable in its fullest development are embraced in four groups—perception, the intellect, the emotions, and the will. Either one of these may be exercised independently of the others. Thus, an individual may have a perception without any intellectual, emotional, or volitional manifestation, and so the intellect, the emotions, or the will may be brought into action without the necessary participation of each other. It is, however, clearly established that all mental processes of any kind have their origin in perception, and that an individual born without the ability to perceive, either from defects in the external organs of the senses, or of the central ganglia by which impressions on these organs are converted into perceptions, would be devoid of intellect, emotion, and will—would be, in fact, lower in mental development than the most degraded types of animated beings. He would not, in fact, be able to conceive of so simple an idea as that one and one make two. How could he, unless he could see two objects, or hear two sounds, or smell two odors, or taste two flavors, or feel two tactile impressions? There would be no means by which he could differentiate one from two, for no knowledge on the subject could reach his brain. Though he might have the intellectual potentiality of Socrates, he would be an actual imbecile, without the slightest mental scintillation. The brain and other nerve-centers can only act from impressions received from without.
Perception is, therefore, the primary manifestation of mind, and is that part the office of which is to place the individual in relation with external objects. Thus an image is formed upon the retina, the optic nerve transmits the excitation to its ganglion, this at once functionates, the force called perception is evolved, and the image is perceived. If the retina be sufficiently diseased, the image is not formed; if the optic nerve is in an abnormal condition, the excitation is not transmitted; if the ganglion is disordered, the perceptive force is not evolved. Therefore, in order that a true perception may be experienced, an organ of sense, a nerve, and a mass of gray nerve-tissue are necessary, and no other organs are required.
It is rarely the case that an individual perceives an impression made upon any one of the organs of the senses without a higher mental operation being performed. This is especially the case when the perception is of such a character as to be irritative. Thus, if an exceedingly bright light be allowed to impinge upon the retina, the brows are corrugated, and, if it be still more intense, the eyelids are closed so as to shut it out altogether; if a very loud noise strikes upon the tympanum, the head is turned so as to prevent the undulations of the atmosphere reaching the ear in full force; if the skin be irritated, the part is, if possible, drawn away, and, if the irritation be so great as to excite pain, the whole body is thrown into contortions and efforts are made to escape. Some of these movements appear to be involuntary, and even to be performed in direct opposition to the will, and then they are said to be reflex—that is, that they are the result of the conversion of a sensation into a motor impulse without the accompanying action of any ganglion, the action of which is the evolution of volitional force.
Now, it is very true that some of the actions in question are apparently altogether involuntary, and are thus true reflex movements, and it is no difficult matter to separate them from those other which are clearly volitional, determinate, and performed with a definite purpose in view. If, for instance, an irritative substance be applied to the interior of the nostril, the action which we call sneezing is produced. This consists of a spasmodic contraction of certain muscles by which the air in the lungs is forcibly expelled through the nostrils. It is automatic and preservative in character, the object being to get rid of the offending substance. It is always performed in the same way, the muscles brought into action are always the same, and it is spasmodic, sudden, and without deliberation or judgment, so far as we can determine from our own consciousness. Again, if the soles of the feet are tickled, they are drawn away, although it is possible for the impulse to remove them to be restrained by the exercise of the will, and, indeed, some individuals can prevent sneezing by strong volitional power evolved from the higher ganglia of the brain. But let us suppose the case of a man with a disease of the upper part of the spinal cord of such a character as to prevent its conveying volitional impulses from the brain to the muscles of the lower limbs; now let the soles of the feet be tickled, and we shall find that they are drawn away, and generally with very much more force than when the brain is allowed to act. Such a movement is probably one of true reflex character; it is spasmodic and indeterminate, being more extensive than is necessary. But let us go still further in our suppositions, and imagine that in such a case the mere drawing away of the foot was not sufficient to avoid the irritation, and that the individual deliberately lifted up the other foot in the attempt to remove the offending object, and that this action not proving adequate, he made two or three leaps in order to escape. What would we call these movements? Would they not be evidence of perception and will? Would they not be movements performed with a definite purpose—the very best possible under the circumstances—to escape from the irritation, even though the brain were unconscious of them? It must be remembered that consciousness is not the necessary accompaniment of volition, as we shall presently see from examples I shall adduce; and this being the case, I can not avoid the conclusion that actions performed under the circumstances I have stated would be based upon perception and done through the power of volition.
Warm-blooded animals are for many reasons not suitable subjects for experiments such as are required in the study of the phenomena under consideration, but in some of the lower animals, as the frog, for instance, we find those conditions present which fit them for such investigations. Thus, if the entire brain be removed from a frog, the animal will continue to perform those functions which are immediately connected with the maintenance of life. The heart beats, the stomach digests, and the glands of the body continue to elaborate the several secretions proper to them. These actions are immediately due to the sympathetic system, though they soon cease if the spinal cord be materially injured. But, in addition, still more striking movements are effected—movements which are well calculated to excite astonishment in those who see them for the first time, and who have embraced the idea that all intelligence resides in the brain. For instance, if in such a frog the webs between the toes be pinched, the limb is immediately withdrawn; if the shoulder be scratched with a needle, the hindfoot of the same side is raised to remove the instrument; if the animal is held up by one leg, it struggles; if placed on its back—a position to which frogs have a great antipathy—it immediately turns over on its belly; if one foot be held firmly with a pair of forceps, the frog endeavors to draw it away; if unsuccessful, it places the other foot against the instrument and pushes firmly in the effort to remove it; still not succeeding, it writhes the body from side to side, and makes a movement forward.
All these and even more complicated motions are performed by the decapitated alligator, and in fact may be witnessed to some extent in all animals. I have repeatedly seen the headless body of the rattle-snake coil itself into a threatening attitude, and, when irritated, strike its bleeding trunk against the offending body. Upon one occasion, a teamster on the Western plains had decapitated one of these reptiles with his whip, and, while bending down to examine it more carefully, was struck by it full in the forehead; so powerful was the shock to his nervous system that he fainted and remained insensible for several minutes. According to Maine de Biran, Perrault reports that a viper whose head had been cut off moved determinedly toward its hole in the wall, I have performed a great many experiments and made numerous observations relative to the matter, and have for a number of years taught, in my course of lectures on diseases of the mind and nervous system, the doctrine now set forth that, wherever there is gray nerve-tissue in action, there is mind. Into the detail of these experiments it is scarcely proper on this occasion to enter; suffice it to say that they all go to establish the fact that the spinal cord, after the complete removal of the brain, has the power of perception and volition, and that the actions performed are to all intents and purposes as perfect of their kind as they would be were the brain in its place.
As I have said, it is difficult to perform experiments of the kind in question on warm-blooded animals, for the hæmorrhage that results in consequence of the necessary cutting operation soon leads to the loss of life; but, for all that, we are not without information on the subject, derived from investigations of some of the higher animals. You have, most of you, seen a decapitated chicken staggering and fluttering about the barn-yard. Whence comes the force by which its movements are made, unless from other organs than the brain? This is a rough experiment that is performed every day, but in the laboratory we do it in a more careful way, and the results are still more striking.
If the brain be entirely removed from a pigeon, the bird turns its head in accordance with the motion given to a lighted candle held before its eyes; it smooths its feathers with its bill when they are ruffled; it places its head under its wing when it sleeps; it opens its eyes when a loud noise is made close to its head. Onimus removed the brain from young ducks hatched and brought up by a chicken. These ducks had never been in the water, yet when placed in a basin they immediately began to swim. Their motions in swimming were as regular as in other ducks which had lived in the water. This series of experiments shows that even the inborn instinct of animals is not solely resident in the brain.
Now, when we come to man, and observe the experiments which are constantly being made for us, both in health and disease, we can not avoid placing the spinal cord much higher as a nerve-center than it is usually placed by physiologists.
In human anencephalic monsters, or those born without a brain, we have interesting examples of the fact that the spinal cord is possessed of perception and volitional power. Syme describes one of these beings which lived for six months. Though very feeble, it had the faculty of sucking, and the several functions of the body appeared to be well performed. Its eyes clearly perceived the light, and during the night it cried if the candle was allowed to go out. After death the cranium was opened, and there was found to be an entire absence of the cerebrum, the place of which was occupied by a quantity of serous fluid contained in the arachnoid. The cerebellum and pons Varolii were present. Panizza, of Pavia, reports the case of a male infant which lived eighteen hours. Respiration was established, but the child did not cry. Nevertheless, it was not insensible. Light impressed the eyes, for the pupils acted. A bitter juice put into the mouth was immediately rejected. Loud noises caused movements of the body. On post-mortem examination, there was found no vestige of either cerebrum or cerebellum, but the medulla oblongata and pons Varolii existed. There were no olfactory nerves; the optic nerves were atrophied, and the third and fourth pairs were wanting; all the other cranial nerves were present.
Ollivier d'Angers describes a monster of the female sex which lived twenty hours. It cried, and could suck and swallow. There was no brain, but the spinal cord and medulla oblongata were well developed.
Saviard relates the particulars of a case in which there were no cerebrum, cerebellum, or any other intracranial ganglion. The spinal cord began as a little red tumor on a level with the foramen magnum. Yet this being opened and shut its eyes, cried, sucked, and even ate broth. It lived four days.
Mr. Lawrence has published the details of a very interesting case in which there was no brain. But the excito-motory functions were well performed. The child moved briskly and gave evidence of feeling pain. Its breathing and temperature were natural, and it took food. Movements such as these do not afford evidence of a very high degree of intellect, but they are precisely such as are performed by all new-born infants possessed of brains. If they are not indicative of the existence of mind, we must deny this force to all human beings on their entrance into the world.
But we are not obliged to rest on the phenomena afforded by anencephalic monsters for all the evidence that the spinal cord of man is a center of perception and volition. We have only to observe the manifestations of its action which are of daily occurrence in our own persons. And in bringing them to your notice I shall quote from a little work on "Sleep and its Derangements," which I wrote a few years ago:
"If an individual engaged in reading a book allows his mind to be diverted to some other subject than that of which he is reading, he continues to see the words, which, however, make no impression on his brain, and he turns over the leaf whenever he reaches the bottom of the page, with as much regularity as though he comprehended every word he had read. He suddenly, perhaps, brings back his mind to the subject of his book, and then he finds that he has perused several pages without having received the slightest idea of their contents.
"Again, when, for instance, we are walking in the street and thinking of some engrossing circumstance, we turn the right corner and find ourselves where we intended to go, without being able to recall any of the events connected with the act of getting there."
In such instances as these—and many others might be adduced—the brain has been so occupied with a train of thought that it has taken no cognizance or superintendence of the actions of the body. The spinal cord has received the several sensorial impressions and has furnished the nervous force necessary to the performance of the various physical acts concerned in turning over the leaves, avoiding obstacles, taking the right route, and stopping in front of the right door.
All cases of what are called "absence of mind" belong to the same category. Here the brain is completely preoccupied with a subject of absorbing interest, and does not take cognizance of the events which are taking place around. An individual, for instance, is engaged in solving an abstruse mathematical problem. The whole power of the brain is taken up in this labor, and is not diverted by circumstances of minor importance. Whatever actions these circumstances may require are performed through the force originating in the spinal cord.
The phenomena of reverie are similar in some respects to those of somnambulism, to which attention will presently be directed. In this condition the mind pursues a train of reasoning often of the most fanciful character, but yet so abstract and intense that, though actions may be performed by the body, they have no relation with the current of thought, but are essentially automatic, and made in obedience to sensorial impressions which are not perceived by the brain. Thus, a person in a state of reverie will answer questions, obey commands involving a good deal of muscular action, and perform other complex acts, without disturbing the connection of his ideas. When the state of mental occupation has disappeared, there is no recollection of the acts which may have been performed. Memory resides in the brain, and can only take cognizance of those mental acts which spring from the brain, or of impressions which are made directly on the encephalon.
In the case of a person performing on the piano and at the same time carrying on a conversation, we have a most striking instance of the diverse though harmonious action of the brain and spinal cord. Here the mind is engaged with ideas, and the spinal cord directs the manipulations necessary to the proper rendering of the musical composition. A person who is not proficient in the use of this instrument can not at the same time play and converse with ease, because the spinal cord has not yet acquired a sufficient degree of automatism. Darwin gives a very striking example of the independent action of the brain and spinal cord. A young lady was playing on the piano a very difficult musical composition, which she performed with great skill and care, though she was observed to be agitated and preoccupied. When she had finished, she burst into tears. She had been intently watching the death-struggles of a favorite bird. Though the brain was thus absorbed, the spinal cord had not been diverted from the office of carrying on the muscular and automatic actions required by her musical performance.
In somnambulism the brain is asleep, and this quiescent state of the organ is often accompanied, in nervous and excitable persons, by an exalted condition of the spinal cord, and then we have the highest order of somnambulic manifestations, such as walking and the performance of complex and apparently systematic movements. If the sleep of the brain be somewhat less profound, and the spinal cord less excitable, the somnambulic manifestations do not extend beyond sleep-talking; a still less degree of cerebral inaction and of spinal irritability produces simply a restless sleep and a little muttering; and when the sleep is perfectly natural, and the nervous system of the individual well balanced, the movements do not extend beyond changing the position of the head and limbs and turning over in bed.
The phenomena of catalepsy, trance, and ecstasy are also indicative of an independent action of the spinal cord, inasmuch as the power of the brain is not exercised over the body, but is either quiescent or engrossed with subjects which have made a strong impression upon it. Some of the manifestations of mind shown under such conditions are exceedingly interesting, and are altogether outside of the domain of cerebral consciousness.
But notwithstanding the fact that the sympathetic system and the spinal cord share with the brain the office of producing mind, there is no question that this lastnamed organ, immeasurably in man at least, transcends them in power.
The brain is by far the largest mass of nerve-substance contained in the body of any animal possessing a brain; indeed, it far exceeds in bulk and weight all the rest of the nervous system together. The researches of European observers give 4912 ounces as the weight of the average brain of the white inhabitants of Europe—the maximum, that of Cuvier, being 6413 ounces, and the minimum, consistent with a fair degree of intelligence, 34 ounces. Webster's brain (allowance being made for disease which existed) weighed 6334 ounces. Dr. Abercrombie's 63 ounces, and Spurzheim's 55116 ounces. The average of twenty-four American brains, accurately weighed by Dr. Ira Russell, was 52·06 ounces—the maximum 64 and the minimum 44·25 ounces. The same observer found the average full negro brain, as determined from 147 specimens, to be but 46·96 ounces.
The capacity of Daniel Webster's cranium was the largest on record, being 122 cubic inches. That of the Teutonic family, including English, Germans, and Americans, is 92 cubic inches. In the native African negro it is 83 cubic inches, and in the Australian and Hottentot but 75. The brain of the idiot seldom weighs over 23 ounces, and it is often much less than this. In one instance coming under my own observation, the weight of the entire brain was but 1412 ounces. Mr. Gore has related in the "Anthropological Review" the particulars of a case of microcephaly in which the brain weighed but 10 ounces and 5 grains. The subject, a female, though forty-two years of age, had an intellect which is described as infantine. She could say a few words, such as "good," "child," "morning," with tolerable distinctness, but without connection or clear meaning, and was quite incapable of anything like conversation. Her habits were decent and cleanly, but she could not feed herself—at least with any degree of method or precision. She was fond of carrying and nursing a doll. In a case described in a subsequent number of the same journal, by Professor Marshall, the weight of the entire brain was but 81⁄2 ounces. The subject was a boy twelve years of age. Nothing is said relative to the intelligence manifested.
Absolutely, the normal human brain is larger than that of any other animal, except that of the elephant and the whale. Relatively to the height of the body, it very greatly exceeds the proportion existing in either. Leuret found the mean proportional weight of the brain to the rest of the body to be in fishes as 1 to 5,668. The range in these animals is, however, very great. In the bass, I found it, as the result of eleven observations, to be as 1 to 523; in the eel, twenty-two observations, as 1 to 1,429; and in the garfish, nine observations, as 1 to 8,915.
In reptiles of different orders Leuret determined the average to be as 1 to 1,321. I found the proportion in frogs to be as 1 to 520; in lizards, as 1 to 180; and, in the rattlesnake, as 1 to 1,825. The brain of an alligator, over six feet in length, which I examined, weighed but a little over half an ounce.
Next in order come the birds, and here we find a very decided increase in the proportion. From many determinations made by Haller, Cuvier, Cams, and himself, Leuret gives the average as 1 to 212. In the tomtit he found it as 1 to 12; in the canary-bird, as 1 to 14; in the pigeon, as 1 to 91; in the duck, as 1 to 241; in the chicken, as 1 to 377; and, in the goose, as 1 to 3,600. These are very great differences, and, as Leuret remarks, have no constant relation to the intelligence. It is worthy of notice that the brain is proportionally smaller in those birds which are domesticated, and which, consequently, do not have to make so severe a struggle for existence, than in the wild birds; and their brains, therefore, are more encumbered by fat. From determinations that I made, it was ascertained that the brain of the canary-bird reared in the United States was in weight compared to that of the body as 1 to 10·5, and in the Arctic sparrow as 1 to 11. No observations on record show proportionally larger brains than these.
Among mammals we find a still greater increase in the weight of the brain as compared with that of the body. Leuret found it to range in the monkeys from as 1 to 22, 24, and 25; in the dolphin it was as 1 to 36; in the cat, as 1 to 94; in the rat, as 1 to 130; in the fox, as 1 to 205; in the dog, as 1 to 305; in the sheep, as 1 to 351; in the horse, as 1 to 700; and, in the ox, as 1 to 750. The mean for the class of mammals, exclusive of man, was as 1 to 186. My own observations accord very closely with those of Leuret. I found that in the prairie-wolf the proportion between the brain and the body was as 1 to 220; in the wild cat, as 1 to 158; and in the rat, as 1 to 132.
If these figures teach anything at all, it is that there is no definite relation existing between the intelligence of animals and the absolute or relative size of the brain. It is true that, taking the data collected by Leuret as the basis, there is a well-defined relation between the mental development and the brain, as regards the several classes of vertebrate animals; for in fishes, the lowest, the brain is but one 5,668th part of the body; in reptiles, the next highest, it is one 1,321st part; in birds, next in the ascending scale, it is one 212th part; and in mammals, the highest of all, one 186th part. There is, therefore, beginning with the lowest class, a regular ascent in the volume of the brain till it reaches the maximum in mammals.
But, when we look at the relation as it exists between the different orders and genera of any one class, we can not say that there is any such variation in the degree of mental development as we should expect to find if the brain were the only source of the intelligence, and some members of the very lowest class have relatively larger brains than certain animals of the very highest. Thus, the brain of the bass is to the body as 1 to 523, while in the horse it is but as 1 to 700, and in the ox as 1 to 750. If the relative size of the brain is to be taken as an indication of the degree of intelligence, we must regard the bass as a more intellectual animal than either the horse or the ox. The lizard has a brain which bears the high proportion to the body of 1 to 180. This is greater than that existing in the fox, the dog, the sheep, and several other mammals. The canary-bird and the Arctic sparrow have brains proportionately larger than those of any other known animals, including man, and yet no one will contend that these animals stand at the top of the scale of mental development. Man, who certainly stands at the head of the class of mammals, and of all other animals, so far as mind is concerned, rarely has a brain more than one fiftieth the weight of the body, a proportion which is much greater in several other mammals, and is, as we have seen, exceeded by many of the smaller birds.
Even in absolute weight, independent of any relation to the rest of the body, the brain of man is not the largest, being exceeded by that of the elephant and the whale. But, when we inquire into the matter of the absolute and relative quantity of gray nerve-tissue, we find that in this respect man stands preeminent; and it is to this fact that he owes the great mental development which places him so far above all other living beings, for it is the gray tissue which originates mind—the white, as is well known, serving only for the transmission of impressions and impulses. Unless regard is paid to this point, we should certainly fall into serious error in determining the relation existing between the mind and the nervous system; but, having it in view, the connection is at once clear and well defined, there being no exception to the law that the mental development is in direct proportion to the amount of gray matter entering into the composition of the nervous system of any animal of any kind whatever.
A point which attracts a good deal of attention at the present day is that which relates to the differences in the brain and mind as exhibited in the sexes of the human species. A few words on this division of the subject may not, therefore, be out of place.
The skull of the male is of greater capacity than that of the female, and it is a singular fact that the difference in favor of the male increases with civilization. Thus, in savage nations, as the Australians and the negroes of Africa, the skulls of men and women are much more alike in size than they are in Europeans. It would appear from this fact either that women, from some cause or other, have not availed themselves of the advantages of civilization, as factors in brain development, to the same extent that man has; or that, among savages, there is not that dissimilarity in mental work that is found in civilized nations; and that, hence, there is not the same necessity for a difference in brain-development.
For it naturally follows that, in the normal skull, there is a correspondence between its size and that of the organ contained within it. Many observations have shown that the average male brain weighs a little over forty-nine ounces, while the average female brain is a little over forty-four ounces, or about five ounces less. The proportion existing between the two is, therefore, as 100 to 90.
This apparently makes a good showing for man, but, when we look at the matter in another and possibly a more correct light, the advantage is rather the other way, for, relatively to the weight of the body in the two sexes, the difference, what there is, is in favor of woman. The body of the female is shorter, and weighs less, than that of the male. Thus, in man the weight of the brain to that of the body has been found to be an average of 1 to 36·50, while in woman it was as 1 to 36·46. I have said that possibly this may be a more correct way of determining the size of the brain than by absolute measurements, without regard to the size of the body. The doubt arises from the fact that we do not know that very thin persons, in whom, of course, other things being equal, the brain would be relatively larger, are more remarkable for mental vigor than very stout ones, in whom the relative size of the brain would be less. Such being the case, it is difficult to believe that the proportionate size of the brain to that of the body has any important influence as a factor in the production of mind. It is the absolute, rather than the relative, amount of gray matter that is to be considered in determining the brain-power.
It must, however, be borne in mind that the quantity of gray matter can not be positively affirmed from a determination of the size of the brain, though in general it can. A person, for instance, may have a large head and a large brain, and the layer of cortical substance be very thin; and another person, with a smaller brain, may have the cortex so thick as to more than compensate for its small superficies. Still, these are exceptional cases. As a rule, the larger the brain, the greater the mental power of the individual.
Another difference between the brain of man and that of woman is found in the conformation of the organ. In man the frontal region is more developed than it is in woman. There is a certain fissure, called the fissure of Rolando, which I point out here on this model. Now, if we take the entire length of the brain as = 100, there will be found in woman 31·3 in front of the upper end of this fissure, while in man there will be 43·9.
Again, the specific gravity of the male brain, both of the white and the gray substance, is greater in man than it is in woman.
It is difficult from these facts to avoid the conclusion that the mind must also be different in the two sexes—not necessarily that one is superior to the other, but that they are different. In some respects that of man excels, in other respects that of woman predominates. It would be a bad state of affairs for mankind if the mind in the two primary divisions of the human race were the same. In barbarous nations, as we have seen, the difference in size is less than it is with civilized peoples, and as one consequence of this fact we find that there is not so great a difference in the mental development. The work of a woman with these is almost the same as that of a man. Her mode of life, her dress, are not essentially different, except in so far as they must be different on account of her sex. But with civilized nations there is variety in modes of thought and in other mental characteristics, in occupation, in manner, in dress, so that the differentiation between the sexes is far more distinctly marked than it is in the nations low in the scale of progress. Who can doubt that this is the direct result of difference, not only in the brain but in other parts of the nervous system? It appears to me, therefore, that while the education of a woman should be just as thorough as that of a man, it ought not to be the same. The two sexes move along paths that approach parallelism at some points of their course, but they can never travel exactly the same road till they have nervous systems presenting exactly the same anatomical configuration and structure.
Another point—and it is one of such practical importance that it would scarcely do for me to pass it over—and that is the influence of age in affecting the relations existing between the mind and the nervous system.
Most civilized communities have enacted laws against the employment of children in severe physical labor. This is well enough, for the muscles of young persons are tender and weak, and not therefore adapted to the work to which cupidity or ignorance would otherwise subject them. But no such fostering care does the State take of the brains of the young. There are no laws to prevent the undeveloped nervous system being overtasked and brought to disease or even absolute destruction. Every physician sees cases of the kind, and wonders how parents of intelligence can be so blind to the welfare of their offspring as to force or even to allow their brains to be worked to a degree that in many cases results in idiocy or death. Only a few months ago I saw for the first time a boy of five years of age, with a large head, a prominent forehead, and all the other signs of mental precocity. He had read the first volume of Bryant's "History of the United States," and was preparing to tackle the other volumes! He read the magazines of the day with as much interest as did his father, and conversed with equal facility on the politics of the period. But a few weeks before I saw him he had begun to walk in his sleep, then chorea had made its appearance, and on the day before he was brought to me he had had a well-marked epileptic paroxysm. Already his mind is weakened—perhaps permanently so. Such cases are not isolated ones. They are continually occurring.
The period of early childhood—say up to seven or eight years of age—is that during which the brain and other parts of the nervous system are most actively developing, in order to fit them for the great work before them. It is safe to say that the only instruction given during this time should be that which consists in teaching children how to observe. The perceptive faculties alone should be made the subjects of systematic attempts at development. The child should be taught how to use its senses, and especially how to see, hear, and touch. In this manner knowledge would be acquired in the way that is pre-eminently the natural way, and ample food would be furnished for the child's reflective powers.
And now I must bring these remarks to a close, although there is a great deal yet that, were there time, and I were not afraid of wearying you, I should be glad to say. One point, however, must not be overlooked, and that is, the occasion that enables me to come before you at all. It is not likely that the world, and especially Pennsylvania, will ever forget the wise man who laid the foundations of this institution of learning. It is not yet venerable by age, but, when it counts as many centuries of existence as it now counts years, the name of Asa Packer will stand first among those that it will delight to honor. More than forty years ago, when I was a boy in Harrisburg, and he was a State Senator from Northampton County, I knew him well, and his personal appearance and manner are firmly fixed in my mind as he was then, a man of perhaps thirty-five to forty years of age. I recollect that upon one occasion I met him at the corner of Market and Third Streets, as he was on his way to the Capitol, and that he invited me to walk with him to the building. I was then a school-boy, and he questioned me very closely in regard to the profession I proposed to adopt. I had then no very positive ideas on the subject. I had thought of the church, of law, and of medicine, and so I told him. We were then about half-way up the board-walk that extended from the corner of Third and Walnut Streets to the Capitol-grounds. He stopped, and, turning to me, said: "Ah, my young friend, the most difficult task you have before you is to make the right choice. A bad start at the beginning is almost certain to result in a bad race and a bad finish. Don't leave it to chance. Think it over, and then decide."
I thanked him.
"One thing more," he said. "If, after you have decided, you find that you have acted hastily and without the knowledge of yourself that was necessary, don't be afraid or ashamed to change. Don't stick to a profession for which you are unsuited merely for the sake of sticking. It is better, however, to be sure in the first place."
Perhaps even at that time he had it in his mind to found this university. The world knows that he made no mistake. He had determined what to do, and how to do it; his brain worked easily and it worked well; and what he apparently did in the way of accumulating wealth for his own advantage was in reality done for the advantage of his fellow-creatures, whom he loved as members of the universal brotherhood to which he belonged.
- ↑ An address delivered at the Lehigh University, on "Founder's Day," October 9, 1884.