THE MECHANISM OF THE BRAIN.

Otago Witness, Issue 2572, 8 July 1903, Page 79

THE MECHANISM OF THE BRAIN.

By Caul SJfcLDER, in Harper's Monthly. The idea ow chemistry of the living body, of bones ltd muscles and secreting glands, is not neW. It was Lavoisier, for example, who showed that the work of the lungs, in taking up oxygen and giving off carbonic acid, is a simple chemical process, like the burning of coal in the grate or the rusting of iion. And the butchers of the French Revolution hid stilled the workings of his splendid brain before the eighteenth century closed. The chemistry of tli3 mind is more recent. It was about a half-century ago that a reflective German, gathering together the scant results of his day, formulated his famous aphorism : "Ohne Phosphor, keine Oeda.ike" (without phosphorus, no thought). That was not the beginning of the endeavour to find out hoy. we think. The anatomist? had been busy for a halfcentury before. And. they have been still more industrious since. Thanks to them, wo have now a marvellous picture of the minute structure of the brain and the nerves. They can follow more or less definitely the path of every exterior sensation, whether it ba one of sight or sound or touch. They can trace even the course of the twinge of pain that tomes, say, when an unprotected toe meets with a mislaid tack, and they can follow more or less the resulting stimulus that makes you cry out, "Oh !" — or something else. And the experimental psychologist of the day will tii*3 this and every other mental process to the fi action of a second. Nevertheless, we are as 3'et only just beginning to see the whole of the pictureit may take another quartet or half-cen-tury before we shall "see it clearly and see it whole," as the late Matthew Arnold was wont to say. Meanwhile it ;s curious to note that the daring guess of Moleschott, of a half-century ago, might still seive iaiily well to describe wluit we know of the chemistry of the brain • , "Obnc Phosphor, keine G-ediinke " ' This is not the way a physiologist of today would phrase it, exac'iv. Tho patient investigator is shy of a pa* phrase, that, after all, tells little. Still, it is a, matter of si.me interest to know that there is 1 substance, as chemically definable, let us fay, as cheese or anthracite coal, which does our thinking. The physical basis of thought and sensation is the biain and the nerves. And the vital part of the brain and the nerves seems to be a highly phosphorised fat, and without the phosphorus this fat does not seem to think. The world of science wa« a long time accepting the notion of a living substance, a chemically analysable basis of life. Huxley'.s celebrated '"protoplasm" lecture did much to reconcile men's minds to this materialistic conception. But it has been a great deal harder to bring man to conceive a thinking substance — a form of matter, like salt or sugar or gunpowder, whose business it is to feel and think and dream. To many the notion is uncanny. The Conclusion, however, seems inevitable. So far a,s we know, the rnocesses of thought and consciousness are associated only with a special form of livinif substance, a particular kind of Huxley's "protoplasm." And protoplasm is a more or less definite substance that tan be, and has been, analysed in the chemist's tube. It is made up. 111 varying propoitions. of the water we drink, the o.wgen and nitrogen of the air we breathe, the carbon of the food we eat. Add a trace of mineial salt«. the salts of iron and others, a little sulphur and phosphorus, and the lis* of elements i.« complete The analysis is difficult— not vet. peihans, absolutely exact. But the irain facts are clear In worm.-, and other lowly types we betrin to find the different parts of the animal connected by thin threids of a highly !-en.«itive substance which conveys a stimulus much moie swiftly than the rest of the body. They are nerves When two' 01 , three nerve« meet at a common point, -we ' have a little .bunch 01 bulb of neivnus sub- ' stance called a ganglion. It is usual'y found near the end which answers to the head. Other ganglia appear as we rise in the scale, but always the one near the head is the lareest. and it acts as a common centre for all the others. It is the beginning of the brain From this .to thp brain of a Helmholtz or a Shakespeare is but a steady and uninterrupted development, through fish and bird and beast, to the . highly-endowed ape, and thence, by insensible gradations, to the finest type of civilised men. It is apparently merely an increase in the number and arr<nieement of the concerting units of ganglia and connecting nerves. And in this orderly evolution there is lie- break, no link nursing anywhere. Whether it be the brain eel' of a glowworm, or one-trembling with the harmonies of Tristan and Isolde, the stuff it i.s made of is much the same ; it is a difference of structure, apparently, lather than of mateual And the chemical difference between a brain or nerve cell and that of the muscles or the skin seems reducib'e mainly to a difference in the proportion of two substances, water and phosphorus Lean beef, for example, is from 70 to 80 per cent, water ; the brain is from 90 to 95 per cent water And a brain or neive cell may contain from five to ten times as much phosphoius as, let. us say. the cells of the liver or the heait The actual quantity is, of course, extremely small —by weight but .1 fraction of 1 per cent. About 31b ivoirdupois of this very complex phosphorised stuff make up an aveia^e human brain. There is 1 '(it nirne of it distributed dnwn one's spinal column : and little plexuses all uver the b d;. , \\h< uvei

a, group of muscles are to be moved ; and others still, the sensory or feeling nerves, which are everywhere. It is hard to find a cubical half-inch outside the bones where they are not.

All told, the nervous substance, which for the sake of making its functions clear I have called the matter which thinks, forms a not inconsiderable portion of the body outside of the bony skeleton. It is made up of distinct and separated units, for the most part extremely minute, though tome attain a length of 2ft or 3ft. These units, for lack of a more misleading name, are called cells. The "cells" which run from the small of your back down into your toes, and wiggle the same, or inform "you when a member of the family is stubbed, are the longest. Those of the" brain are mostly so small as to tax the powers of the microscope; their avenge length would be meantied in thousandths of an inch. There have been many attempts to get at their actinl number; it is certainly large. Computations for the brain alone range from 600 millions upwards. One, due. I think, to .Waldeyer, sets the totai number of brain cells (average) at 1600 millions. This would mean a brain population exceeding the known v popiiljtion of the earth. Of course the number varies enormously, for the size and weight of the noimal brain vary greatly. Tho si/o of the brains of comparatively few d-slin-jriiished men i* knovn. and rfo»t uublNhcd figures are w-thW. The l,st given belo>7 , s authoritative, and speak< for iUelf. The sizes are givui in cubic c^ntimptrt^ .—. —

It will be seen that Byron, who was commonly supposed to have a small head, is lushest in the list ; and whatever may be thought of his poetiy. certainly he was a man of lather mediocre intellectual attainments, as poets genei illy aie ; while Baton Liebig, who posse^spd one of the best-equipped brains of the tiist half-cen-tury, was below the average. 80, too, there is but a shghl dift'eience in the average size of the male and female brain, though the general inferiority of the latter was evident enough up to the latter part of the nineteenth century. Directions for measuring the«size of your own brain, if you -n\ interested, will bp found in any g(.od er-cyclopsedii. or would doubtless be srpplird by the distinguished Professor Wilder of Cornell As the brain i« ko marly all water, it i« evident that the figures for size, in cubic centimelies. express very nearly the weight in grams, and this may be very quickly reduced to ounces and pounds of our antiquated system. In general, the size and weight of the brain vary directly with the size and weight o f the body. It is obvious that a big body will need <i big brain to run it right, for ninetenths of nervous activity or "mental"' action is demoted to the promotion and control of the muscles. A little man with ii big head, then, is apt to possess more of what we call brains than a big man with .1 relatively small head

But there seems another anatomical characteristic of far more importance than size. That i.s the appearance of the brain surface — the cortex, or rind. The brain of a savage or an idiot is lather smooth. That of a highly-developed man or woman is cieased and folded in an extraordinary way — thrown into convolutions, as the neurologists say. And so it seems as if "brains" r.ie a matter of area or brain surface, for the effect of the folding and creasing is to afford more aiea in a given space. In the matter of brain anatomy it is the superficial man, then, who is the great man. And in general the more folds and kinks he has the gieatei will he be

But it ifc not until we penetiate into the fu.er stiucture of the brain that we begin to catch a glimpse of the mechanism of brain action. Countless attemp's had been made to unveil this complicated .structuie, but it was not until an Italian, Profes.-or (iolgi, took up the mitter, about 20 years ago, that any real progress was made. Professor Oolgi found that the inner substance of the nerves, the neivous subrtance par esx-ellence wis extrrjnely avid of ceitain salts of silver; so that if a piece of brain or a nerve be soaked in a solution of these salts the inner paits would be stained a vivid black.

The levehUionx of this simple method, since extended :n various ways, have been of the deepest interest. Speaking broadly, a nerve resembles nothing so much a.s a vigorous tre*. with a big taproot and 1 sLort fat trunk crowned with a wondeiful arborescence. And if yon take a bit of brain and soak it in the staining solution, then harden it. cut it >nto extremely thin slices — ay. a few hundret'ths of an intli thick — and put the thin bit under a power ful microscope, the picture you get i» like <« cross-section '>f an immense forest Tin* trees are crowded together, and roots an-1 the mvn.ul branches interlace in appaiently inextricable confusion. Yet, as the methods grew more and more delicate, so that mi cioscopes of greater power < ould be used. X was seen that this cHiifiiMon i.- only appaient The nerves do branch in a bewildering way. but there seems to be plenty of room: and just now the patient, peisevering students of biain anatomy are divided into two waning camps over the question a.s to whether the nerves ever touch one another at all. The matter :s important, as shedding light on the means by which a neive wave, what we call a sensation or an impulse, travels. An impulse going up or down <i single nerve follows a simple path If. for example, you step upon the point of a t.iek. you gt-t a sharp sensation of pain, and there i.s an answering jeik of your foot off the ground and perhaps an exclamation. It is com parativelv easy to find the neive which tarries the pain wive, and trace it. *-ay. as far as tho h.we-i end of \Ol 1 Tln-ie it enters the netwoik of neive.- which moke up the spinal ganglia.

f From here an automatic response is sent back over another nerve, a motor nerve — or, rather, a set of them — which contracts I the muscles of your leg and foot violently, and pulls them, up, away from the tack. This is what is called simple reflex action, and with it your brain has nothing to do. Meanwhile the pain wave, entering^the ganglion, has set other nerves, which also er-ter the ganglion, into action, and the impulse goes travelling up to the brain, and it is. only when it reaches the brain rind, or cortex, that you become conscious of the hubbub down in your foot. It is as if there had been a smash-up on a railroad, and the nearest station, being notified, hid sent back what help it could, and meanwhile forwarded to headquarteis an account of the smash. The remarkable thing is Ihsvt the message to headquarters does not go through on a direct wire, but thiough a chain of them, apparently linked together. This shows why the question as to whether there is actual contact between one neive and another is so important. If there is no actual contact, how does the nerve wave travel fiom one to another, as it surely doefc? And if there is contact, how does an impulse ever stop, as it surely seems to. do? M. Jules Soury, of the Soibonne, has suggested a solution of all the conflicting ideas such questions raise by supposing that both sides may have <i part of the truth. In other words, he believes that in some cases there is contact, 01 continuity, and that in others there i* a leap. And from this he draws a possible conclusion that is of extreme intenst H>j »vg fc 'ests that in the case of unconscious nervous or cerebral action (by far the greater part of the nervous activity) there is contact ; that we become aware of what is going on only when the continuity is biuken; that the leap is consciousness. Such a view would tluow back the seat of the "divine faculty" from the neives to the thin water -and-jelly-like substance in which they are immersed. Or, supposing that this especial colloid cannot 1 fixed upon as the seat of the highest powers of man, they might be thrown upjn th.it extraoidmarv and rather hypothetical ethei. of which physicists talk so much and knowso little. Whatever be the way the nerve wave travels, it is certain that something tiavels, and that that something is what we call an impulse or a wave. Fur the rate of its travelling can be accurately timed, and, by nn ingenious process, Professoi Richet of Paris believes that he can measure its amplitude, as you can the wave*- of sound or light. '■Quick as thought" does not mean much. A light wave would travel seven times around the equator 111 a second ; and the speed of electricity, unret-irded, is the wme. The nerve wave nvkes only about .1 hundred feet a second. And now we co-Tie to the very marrow of the question: What ;« this wwve or impulse? What is thought? Up to a ycir ago the best answer that could be made was this : A nerve may be stimulated by an eleCri.: cuirent, and muscles set in action; and. conversely, a nerve in action is always accompanied by ■in electrical disturbance — slight, it is true, but strong enough to be measured with accuracy. In an unprejudiced mind the inference wa* easy. As there is no nerve action without the evident presence of electricity, it seenls probable that nerve action, thought, and consciousness, and what in our piesent ignorance we call electricity, are one and the same. This view gained heav-y reinforcements a year ago from some brilliant experiments of Professor Albert P. Mathews, who had been working on ncr» r e stimulation with Professor Jacques Loeb in the University of Chicago. Professor Loeb, and others, had shown that in certain salt solutions an excised heart could be kept beating for hours ; further, that a piece of ordinary fiog's muscle, for example, dipped in the same solutions, would beat rhythmically like a heart. All of these curiou- manifestations could be varied — the rhythmical play hastened, retarded, or stopped simply by changing the quantity of sal*« in the sohition, or by adding different salts. A pinch uf one salt like a potassium salt would hinder the effect of another, sucl) as ordinary table salt (sodium chloride). Professor Mathews took a step farther. Instead of cutting away the nerves from the muscles, he leit them joined at one end, merely separating the nerve enough to let Mie end of it hang ir> s, cup of salt, solution, while the frog's legs were suspended on a frame The rhythmical beat began in a shoit time, just as if the muscles themselves were in the salt bath. Plainly the nerve carried the stimulus, and. so far as any mortal could see, the stimulus was the same as that winch makes a live frog's muscles contract when it jumps. Whence tame tins .stimulus? The only solutions which give this effect aie those capable of generating a current of oh etricity. A succe-.->.ioi* of electrical im-pulses-from a dynamo, for example — will make the frog's legs < witch rhythmically, just as do thesj electrical solutions. If we cut out all needless assumptions or suppositions whatever, then we shall say that the electric cnirsnt from a machine and the nervous disturbance generated by the salt solution are identical And as the twitch aroused by dipping the end of the neive in a salt bath is exactly the same as occurs when the frog is alive, then we n.ust say that a nerve current, or nerve wd\-^. is electrical in character. If this frightens no one. then we may add that th«* excitation which moves, the legs of a f'otr and that which winks your eve or twirls your flvincr fingers over Ihe pinno keys aie absolutely the same, and are due to "the same cause. And now for the final plunge into what Huxley satirically called- the dank morasses of materialism. * You are seated at the )>iano; the inflection of a jumble of dots on the nag? of mu<sio falls upon the retina of your eve: their position. Mze. and shape aie telegraphed to tour bi tin, '10m which comes .1 seiie« of orders to aims and finaeiN you ue phiving ,•• Chopin Nocturne. Piovided you have spent months or

years in patient and often painful practice, you can do all this, and be talking to a friend at the same time, hardly conscious either of the action af your hands or of the glowing melody being thus mechanically produced.

But between this astonishing achievement and the beginning there have been countless hours wheie every crook of a jingeii end every twisty note was a matter of the most laborious consciousness. This we call thought. In terms of brain physiology it: is the stimulation of a chain of brain cells either by nerve currents from other celte of the brain or from without the brain— < as, for example, from the retina. Whati ever thought or conscio lsne&s may be in itself, it can be defined in physical terms as the stimulation of a 1 datively wide area of the biain — that is to say, the simultaneous activity of a large number of brain cells. The action becomes unconscious when the area or number is lessened.

Thi.« stimulation of a wide area can be erected only by means of nerve connections between the different cells. These connections are known as association fib'es. and are easily discernible by the microscope. Their number is immense. Many cells have scores and even hundreds, and as the cells aio numbered by hundreds of millions it h easy to see that they reach to an unthinkable sum.

It is by means of the^e association fibres that we have what is called association of ideas. Clever people evidently are well piovided with association iibres. Wheie these fibres are lacking theie will be no stimulation of a wide area, and theiefore no consciousness. This is the case of the lower forms of life, and in new-born animals, including babies. In all rf these the anatomical demonstration is prrfecU;v\<-lear. To ascribe consciousness in the ordinary smse to worms, oysters, oc new-bom children has apparently little foundation. In. the case of conscio.i? action becoming automatic and unconscious, as in learning the piano, learning to write, etc., we may infer that constant use (stimulation) tenet* to establish a direct path, which the niive wave will follow exclusively rather than spiead. cut over a wide area, as when the resistance of all the paths was more or '.ess equal. • 13c this as it may, the especial thing in note is that the currents or waves which stimulate tire cells of the brain differ no vhit from those which set jumping the dead muscles of the hind legs of a dead frog. In the one case, :»s in the other, it is caused by, or rather is, a variation of electric potential. There are some to whom new definitions aye distasteful. To define the highi-.-t faculties of the human mind in terms of what; they contemptuously term brute force is, to some persons, a lepiehenMble proceeding, callinir for opprobrium So when Huxley defined life in terms of water, ammonia, and salt 40 years .isro, unpleasant things were said To rid him^alf of the epithet: of "crass materialist" he had recourse to the subtleties of the good Bishop Berkeley.

For this there is ntf nead now. In a recent book, "The Response of Matter," the distinguished physicist of Calcutta, J. Chunder Bose, has done much to strike down the last distinction between living matter and dead. Just as there is no longer a "missing link" in the chain oi Darwinism evolution, so there is no longet a dividing line between plant and animal, between mineral and vegetable, between the animate and the inanimate. In some obscure degree all matter lives.

— Im a recent paper on "Electric Automobiles," read before the Inst 'cut-ion r>f Civil Engineers, Mr H. F. Joel state J that in London aloro there were ovct 16,000 licensed hor.=e carriages, apart from privata vehicles, tradesmen's vans, etc., and it was estimated that ov -r 200,000 horses were stabled each night in London, necessitating the daily removal of more than 5000 tons of mamure and refute.

Average hu.naii biatn, 1-lOOccm. (490z ay ) Dr Dollmger .. 1207 A-as-iz .. isloi sl o Earless .. .. 1-238 Thackeray .. 1644 Jambetta .. 1234 ss c .h l'er '.. . 1781 -icbig .. .. 1352 Cuvid .. .. 1529 lirchoff .. .. 1452 Turgcmcff .. 2012 3roc « •• •■ 11^5 Bjron .. .. 223S Jauss .. .. 1492