DOUBLE-BARRELLED BRAINS.
AWRITER in the February Cornhill has expounded an hypothe- sis of Dr. Brown-Sequard,—the great physiologist (and vivi- zectionist), who has studied so long and so earnestly the rationale of the nervous processes,—that either side of the brain is competent to perform almost all the functions of the brain, just as either eye, -or ear, or lung, is competent, if properly disciplined, to discharge, less accurately, but still tolerably, almost all the functions usually discharged for us by both in combination. Professor Brow n -Sequard fancies that it may be to some extent our own fault that we are so dependent as most of us appear to be on the left side of the brain for the power of intellectual work, and especially for the power of speech and writing, and probably to a great extent, too, in his view, of correct thinking. He suggests that the effect of training children so much more to the use of the right hand and side than of the left, is, that the left side of the brain, which provides the nervous apparatus by which our right arm and side are governed,—just as the right side of the brain provides the
, nervous apparatus by which the left arm and side are governed, —gets a much larger allowance of blood and of the nutrition which . blood brings than the right, the rule always being that in pro- portion to exercise or disuse an organ attracts a larger or smaller supply of aliment from the circulating system, so that to that which has there is given more, and from that which has not is taken away even that which it has. Hence the early predominance given to the use of the right hand and arm in - children, results, according to Professor Brown-Sequard's sug- gestion, in the earlier and fuller development of the left side of the brain ; which, again, results in the left side of the brain being --chiefly used for intellectual and discriminative work. We become in this way unable, he thinks, to use adequately not only our left • hands, but also our right brains, which supply the nervous pro-
-ceases regulating the left hands ; and hence, if any disease attacks the left side of the brain, the work of life has to be begun all over Again with the right brain, the patient having to learn to read and -write and think with an organ quite unaccustomed to the work, and being, therefore, compelled to begin with the most rudi- mentary efforts, just as he did in his childhood, when he was first training the left side of the brain to its duty. He thinks, then, that if children were always taught from the first to do everything with equal ease with either hand,—to use the knife, or the gun, or the painting-brush, or the cricket-bat in the right hand one week and in the left hand the next, so that neither side of the body should have the preference over the other, the effect would
be that both sides of the brain would in childhood be equally nourished, so that the intellectual efforts, when first they begin to tax the brain, would be associated equally with either side of it. And in that case he thinks that if disease struck either side of the brain, the other would be just as much in a position to carry on the work of writing and the other functions -of the intellectual powers, as either lung now is to oxidise the - blood, if the other fails us. We should no longer find what is called aphasia,' or incapacity to catch the right words for our ideas, produced by an injury to the left side only of the brain, for the right side of the brain having been just as much used as the left in the work of selecting words to express our thoughts, it would take up the whole duty of that selection with ease, directly the other failed to do it, just as the sound lung, or the sound side of the other duplicate organs, is ready to accept, and soon grows able
to perform, double duty, as soon as the incapacity of the other side is clearly established. Indeed, if we may trust the Cornhill writer, Dr. Brown-Sequard goes further. He thinks that the work of what we may call double-barrelled brains would, perhaps, be better and more thoroughly sound and vigorous than that of the single-barrelled brains which are at present almost uni- versally in use. There may be something, suggests the reviewer, of the same moral advantage in the use of a double brain directed upon the same problem, that there is in the use of both eyes for the observation of the same object. As those who use both eyes to observe an object, gain some knowledge as to its dis- tance by the muscular adjustment necessary to focus both eyes upon it, so, suggests the reviewer, it may be that the use of both brains for thought or speech may give us, as it were, a more stereoscopic view of the idea we are trying to grasp or express than we could gain from the use of one alone,—some faint reflection, say, of the advantage which we get from comparing thoughts on any difficult subject with somebody else, whose experience and training have been different from our own. Only, even admitting Dr. Brown- Sequard's general view, this assumption implies that after all, though each side of the brain may have been equally developed, it commands the avenues to a different stock of associations, and is not a mere duplicate of the other. If the left eye occupied. pre- cisely the some position in space in relation to the object observed which is occupied by the right eye, binocular vision would be no more stereoscopic than single vision. And so if the right brain embodied precisely the same physical vestiges of experience as the left,—the same, and no others,—there would be no new element of insight added by the use of both brains to those which are contri- buted by the use of one. But if we may trust the authority in the Cornhill, it is pretty clear that Dr. Brown-Sequard, though he fancies that by proper care either brain might be so far developed as to discharge adequately the functions of the other, does believe that each side of the brain has a special aptitude for a special kind of work, which we may call the masculine and feminine sides of the intellect, the left brain being specially competent for in- tellectual work, though not incompetent for emotional, while the right brain is specially competent for the elaboration of feeling, though not incompetent for that of thought. The right aide of the brain is the one most apt to be affected, according to Dr. Brown-Sequard, in all hysterical diseases, as also to be most concerned in all work in which the nervous system contributes to the nutrition of the body. Hence, even if they be equally de- veloped and worked, Dr. Brown-Sequard's theory supposes that intellectual work elaborated through the exercise of the right brain would usually have a larger element of feeling and instinct in it, while the same work elaborated through the exercise of the left brain would be one of drier calculation, of soberer reasoning. Hence, the work of a double-barrelled brain, in which both brains were focussed on the same problem, would, according to this ingenious hint, be superior to ordinary intellectual work, in this, that con- verging trains of thought and feeling would be brought to bear on the same point.
It hardly needs pointing out that the practical defect of this ingenious suggestion is the very inadequate means it supplies of se- curing that both sides of the brain shall be equally exercised,—sup- posing, what is at present hardly more than a mere guess, that the functions of both brains are so far the same that either will discharge adequately the functions of the other. We can secure the exercise of the left arm and leg, because we know perfectly well when we use our left and when we use our right limbs. We can learn, if it be worth while, to carve, and write, and dig, and shoot, and shake hands with the left hand as easily as with the right. But we cannot learn to use the right brain equally with the left, be- cause we have absolutely no means of knowing which of the two we use, or for that matter, whether we use either or both, when we think, and feel, and hope, and dream, and calculate. If Dr. Brown-Sequard or any one else could discover for us a secure mode of laying one side a the brain to rest, so that we could be certain, if we were thinking at all, that the other was the one in use,—if there were any mode of diminishing the supply of blood for a time to one side of the brain and increasing it to the other, so that the brain better supplied might be used, and the other rested, there would be some chance of answering for an equal develop- ment. But as Dr. Brown-Sequard trusts entirely to the very doubtful and indirect results of taking care that children should gain as much command of their right arms, hands, and sides as of their left, in the very sanguine hope that, as a consequence, both sides of the brain would start on a level with each other, and neither of them, therefore, get more exclusively appropriated than the other to intellectual work, it is quite obvious that even if his advice be followed, we shall be no nearer to any certainty that both sides of the brain are equally used in cerebration than we were before. At the best, all that will have been done will be that we shall have stopped off one possible, and perhaps rather minute, cause of inequality of develop- ment, but not that we shall have provided for equality of develop- ment. But even if we could so provide, Dr. Brown-Sequard's hope might not be realised, but falsified, even arguing on the basis of his own assumptions. For it might very well happen that as it assuredly takes longer to gain the highest degree of equal skill with both hands in any manual operation than it takes to attain that degree of skill with one only, so, if by any means we could secure that each side of the brain should be developed pan i passu and only pan i passu with the other, we should gain, in the same time, not a greater brain-power than before, but a less. It is quite true, of course, that a person who has the highest degree of skill with both hands is far more capable of great manual feats than the person who has the highest only with one. But then if he takes, say only half as long again, or more, to acquire it, he must neglect something else which otherwise he might have learned to do with one hand in that time; and so, it might very well be, that even if we could provide for the equal develop- ment of both side a of the brain, the only effect would be that for mortals, whose length of life seldom exceeds threescore years and ten, the double-barrelled brain would never reach the fineness and delicacy of development which is now easily reached within that time by one side alone. And especially is this probable, if it be true, as Dr. Brown-Sequard is said to think, that each side of the brain has at present specific functions of its own, though not exclusive ones. This is not so with regard to our hands. With ordinary men, the left hand only does the right hand's work rather less effectively, and has no specific aptitudes of its own. But if the right brain be, as we are told on Dr. Brown- &guard's authority, specially related to the feelings, it might well happen that in training it to discharge adequately the work of the left side of the brain, it would lose some of its own specific qualities ; and the same thing might be true, mutatis mutandis, of the left side of the brain. On the whole, we think we may say that even accepting implicitly the assumptions of Dr. Brown-Sequard, there is yet almost as little evidence to recommend his practical suggestion as there would be if these assumptions had never been granted. No more remotely contingent inference was probably ever drawn from exceedingly doubtful premisses, than his.
The chief fascination of the theory is furnished, however, in all probability by its apparent explanation of the pheno- mena of a dual consciousness in man,—the sane and the insane side of some men's thoughts,—the good and evil side of all men's thoughts,—the alternations of consciousness in a few re- markable cases of disease between two distinct lives of memory and experience, in one of which the patient remembers one set of persons and one set of facts, while in the other he remembers a quite different set, and sometimes even attaches quite different conceptions to the same person, in accordance with the different chains of association he has connected with him in the two different states. Dr. Brown-Sequard's theory would explain this last pheno- menon by saying that, whenever the injured side of the brain lapsed into inactivity, the intellectual impressions connected with the nervous work it had discharged disappeared, while the other side of the brain came into operation with an entirely new and only recently commenced set of impressions ; and that when the repose of the injured brain had restored it to activity, the uninjured side of the brain would immediately revert to the ordinary duties it had dis- charged before the injury took place, while the trace of its newer work would be extinguished in the reawakening of the old trains of impression. That, however, if an ingenious, is obviously a totally conjectural theory. Even if the explanation really covered the phenomena so far as regards the injured side of the brain, yet why should the healthy side of the brain lose the trace of its recent work when it resumes the discharge of its old func- tions? It seems to us that while no sound physiologist can deny the close and intimate connection between the state of the brain and the state of the mind, the phenomena of colloquy with oneself, in which each side of the controversy is taken in turn by the mind,—the still more remarkable phenomena sometimes found after serious fevers or other injuries to the brain, which result in alternating lives, —and many similar phenomena observed amongst the insane, can never be explained by any merely physiological theory, whether of a double brain or otherwise. All of them in- dicate the existence, no doubt, of various distinct and sometimes utterly disjointed trains of association, by which the mind is prompted to very different and sometimes completely inconsistent conclusions ; but none of them are intelligible at all without assuming one mind, as distinct not only from a brain, but from. two minds, wherewith to judge these associations and to draw con- clusions from them. The very difficulty and puzzle of the matter consists not in any appearance of two distinct judging and willing powers exercising a separate control of the same bodily organism., but in the very different kinds and classes of impressions present to the mind at different times, from which the same judging and willing power appears to draw at those different times, what turn out, of course, to be totally inconsistent inferences. We doubt if any of these phenomena, among the sane or the insane, come to- more than this,—that unhealthy brains give rise to all sorts of de- ficiencies of memory, and defective, and therefore delusive, asso- ciations, sometimes so seriously delusive that the same objects re- present altogether a different nucleus of impressions at different times to the same person. But that certainly does not in any way suggest that each brain represents a mind, or anything at all like it. The double-barrelled brain of Dr. Brown-Sequard, even as his reviewer in the Cornhill describes it, offers no support to the hypothesis of a double personality in the only sense in which that conception could be interpreted.
Previous page
