HAVE WE TWO BRAINS?

New Zealand Graphic, Volume IX, Issue 18, 30 April 1892, Page 456

HAVE WE TWO BRAINS?

UY

WILLIAM A. HAMMOND, M.D.

H E human brain consists of two hemispheres, very much alike in their general appear|Z ance > an d closely united at certain points, il\ H but nevertheless so distinct one from the ®fiS other that it appears strange that they should so long have been regarded as constituting a single organ. When we look into their physiology we find so many arguments for considering them as different in their functions that our astonishment is increased when we think that they are still spoken of as ‘ the brain.' I shall endeavour to show that these two hemispheres are in reality two brains, as much so as our hands are two hands, and our eyes two eyes. As a matter of fact the eyes are just as much united one to the other as one hemisphere of the brain is united to the other hemisphere; and yet we can see with one eye without seeing with the other ; we can even see differently with our two eyes. So we can also think with one brain hemisphere without thinking with the other. We can think of one subject with one hemisphere, and of another subject with the other hemisphere. We can be sane with one, and insane with the other ; the one may have hallucinations which the other corrects ; the one may be stricken with terror while the other is moved with the keenest delight; the one may be disgracefully feeble in will-power while the other carries everything before it ; the one, when the seat of injury or disease, causes one side of the body to be paralysed, while at the same time the other, the seat of some different disease, throws that side of the body with which it is in relation into violent convulsions.

In the very beginning of the existence of the individual the body consists of two distinct halves, which, afterwards becoming fused together, retain, nevertheless, in a great degree their original characteristics. Thus the two sides of the face are never exactly alike ; the two lungs are not of the same size ; the liver is placed on one side of the abdomen, the spleen is placed on the other, and the two brains, though looking much alike, are seen upon close examination to be different and to be possessed of different functions.

The organ of speech is located entirely, in the great majority of cases, in the left brain—occasionally in the right brain—but never, so far as our knowledge extends, in both brains in the same person. Thus if a man be injured in his left brain at a point a little above and in front of the ear, he is deprived of the faculty of speech, losing even all idea of language. If the injury admits of relief, the capacity for speech is at once restored. If, however, the injury takes place on the right side, there is no interference with the faculty of speech—unless, as occasionally happens, the speech organ is situated on that side. Again, if a person is, for instance, shot or otherwise injured in his right brain, he is paralyzed on the left side of his body ; while if correspondingly injured in the left brain he is paralyzed on the right side of his body. Thus the right brain presides over the left side of the body and the left brain over the right side of the body, the nerve fibres crossing to the opposite sides before reaching the cranium. When a physician is called to a case of apoplexy, for instance, and finds his patient without the power of motion and of feeling in his right arm or right leg, he knows that he is suffering from some disease, probably the rupture of a blood vessel, in his left brain ; and with this paralysis there will frequently be a loss of the power of speech. If, on the other hand, the patient is paralyzed in his left arm and left leg, there is no loss of speech and the physician knows that the disease is seated in the right brain. Such facts go to show that there are two brains presiding over opposite sides of the body. By hallucinations we understand a false sensorial impression, which has no real physical basis of truth. Hallucinations may exist with all the senses. Now it occasionally happens that these hallucinations are present with only one eye or one ear or one nostril, or one side of the tongue or the lingers of one hand. A patient of my own, while preparing for bed one night, saw before her the figure of her mother, who had died several months previously. The image did not for an instant impose upon her intellect: but thinking that something must be the matter with her eyes, she closed them alternately and rubbed them with her fingers as we often do when we wish to make our vision clearer. As she closed the left eye the image was no longer perceived ; and then she became convinced that she saw it with the right eye only.

Another patient who had greatly overtasked his mental powers, heard a voice whispering to him to go and kill himself ; but only in the right ear. In both these instances, and in several of similar character that have come under my observation, but one brain was affected, while the other remained free from perceptional disorder. Some of the phenomena of hypnotism are interesting in this connection. In the case of a gentleman upon whom I frequently experimented it was easy, after I had hypnotised him, to act separately upon his two brains. Thus I would place on the middle of his forehead a book, in such a way that it was interposed as a screen between the two eyes so that both could not follow the same line of vision. I would then tell him, for instance, to look with his right eye into a corner of the room, and that there he would see

the dead body of a dear friend. Instantly the corresponding side of his face experienced the greatest horror, while the other remained a perfect blank. I would then tell him to look into the opposite corner with his left eye, where thei e was a clown performing various ludicrous antics. Immediately that side of his face expressed intense pleasure and expanded into a broad smile. Thus there existed in him at the same time two opposite emotions, the one of horror, the other of mirth. Snch experiments appear to me to show indubitably the existence of two separate and independent brains, capable of being influenced in diametrically opposite directions. Nothing, I think, in the whole range of physiological experimentation can give us more conclusive results, unless perhaps it may be the phenomena of double consciousness, to which in the next place I desire to call attention. In this very remarkable condition, a person under the influence either of disease or of injury of one or the other brain lives two separate and distinct lives, as different from each other as though he were in reality two individuals. Several such instances have occurred in my own practice ; but before citing them I will quote the wonderful instance of a French sergeant, who was wounded by a rifle ball on the left side of his head, and who in consequence became paralyzed on the opposite side of his body. He was apparently cured of the wound and of the paralysis ; but shortly afterward a new condition of the most striking character developed. In his ordinary state the patient was quite an intelligent man ; and having been retired from the army he was able to gain his own living by singing in one of the cafes of the Champs Elysees. He was docile and well disposed, and his conduct generally was such as to be beyond reproach. His health was in all respects excellent. Suddenly, however, an entire change took place in his mental characteristics. He forgot absolutely every event of his past life, and yet he acted in all respects as if he was in the full exercise of his senses and of his intelligence, so that a person coming into association with him would never have suspected that he was otherwise than in his normal condition. But his character had undergone a complete change; and above all, he had developed a disposition to steal whatever he could lay his bands upon. After this state had lasted a variable period, sometimes two or three months, he suddenly resumed his natural life, and became in every respect as he was before ; but entirely oblivious of events that had occurred during his abnormal condition.

These two phases of his life continued to alternate, each condition being in close relation with each other condition of the same character. Thus if we designate his normal state by A and his abnormal by B, during every A state he recollected all the events of every previous A state, but had no knowledge of any circumstance occurring during any B state. While in every B state his memory of events which had occurred during every previous B state was full and complete, but he had no recollection whatever of the incidents of any A state. He lived, therefore, two different existences, and undoubtedly the condition was due to the fact that during one period the left brain predominated over the right brain, while during the other the right brain was in the ascendency. In a case which occurred within my own experience, the patient, who had been struck on the head several years previously by a stick of wood so that his skull was fractured, became affected with epileptic convulsions; but he also became a subject of double consciousness. I pon one occasion the attack came upon him just as he was entering a railway train. He proceeded on his journey, and arrived in the city, where he took lodgings at a hotel. A few days afterwards he bought out a small book shop and started into business as a bookseller and stationer. He conducted himself with perfect propriety and apparently was in full possession of his intellectual faculties. He passed, however, under a name different from his real one. During all this period his friends had no knowledge of his wheieabouts until one day when several weeks had elapsed he suddenly resumed his natural condition, and to his intense astonishment recognized his changed circumstances. He at once telegraphed to his friends and returned home, having no knowledge of anything that occurred after getting into the railway train until the tecovery of his natural mental condition.

He has had repeated attacks of a similar character since, and in all of them has a more or less distinct recollection of the events of all like previous seizures, and passes under the same name that he took at first.

Ordinarily the two brains act synchronously, that is to say, at the same time; but when they do not, and there is a difference in their action of the fraction of a second, we have the curious experience that what we are doing at the same time amid the circumstances that surround us we have done at some previous time under identical conditions.

All of us have had such experiences. They afford addisional evidence of the fact that we have in reality two brains, which in these cases do not act at precisely the tame time.