THE LEFT HAND

Evening Post, Volume CXIX, Issue 72, 26 March 1935, Page 10

THE LEFT HAND

IT REMAINS A RIDDLE

DEVELOPMENT OF THE BRAIN

WHAT SCIENCE SAYS

! "I concluded a lecture on 'Dexterity and the Bond Sinister' at the Koyal Institution just twenty-seven years ago with these words: 'We cannot get rid of right- or left-handedness, try how we may,'" writes Sir James CrichtonBrowne in the "Daily Mail."

To "raze out the written troubles of the brain" is no easy matter; to delete its deeply-engraven records is a task impossible.

Ambidextral culture, useful enough in some specially-employed persons, must on the large scale tend to confusion.

Right-handedness. is woven in the brain and so is left-handedness, and to change the pattern you must unravel the tissues. My conviction is that as regards left-handedness it is well to leave well alone.

lam interested to note, therefore, that our London school doctors who have been investigating the teaching of left-handed children have come to the same conclusion as that at which I arrived so long ago.. Their memorandum just presented lays stress on the serious danger that may result from pressure in correcting left-handedness in children when it is either natural or well established.

"Curious," said Carlyle," "to consider the institution of the right hand among universal mankind, probably the very oldest institution that exists, indispensable to all human co-operation whatever; he that has seen three mowers, one of,whom is left-handed, trying to work together ..has witnessed the simplest; form of an impossibility which but for the distinction of the right hand would have pervaded all human things."

. This ' sentence; of * Carlyle's. gives its quietus to thel /"ambidexterity . cult, which from time. to. time obtrudes itself upon us. ~,.. ■;

For if the habitual priority in the use of .the right hand, from Palaeolithic times, has controlled industrial development, regulated .all systems of associated manual activity, the form of tools, the construction ■of machinery, the organisation of sports and games, and even the construction of clothing down to hooks and'eyes, and buttons, it is obvibUs' "that Ahe general adoption of ambidexterity, if that were

practicable, would upset our social and industrial life, introduce hopeless confusion, and multiply accidents of many kinds.

We have no ambidextral race and no left-handed race, but in every righthanded race there are a certain number of left-handed individuals. In the hope of ascertaining the proportion of these to the general population in this country, and of throwing light upon the subject of right-1 and left-handed-ness generally, I circulated some thirty years ago a questionnaire relating to a number of voluntary muscular movements, which through the kindness of friends was placed in the hands of adult.men and women, all of educated ! class—who were requested to mate careful observations and return. the leaflet to me. '

The returns received bore in the first place on the relative frequency of right- and left-handedness in 957 men and women of the educated class, and showed that of these 881, or 92.06 per cent., were right-handed, 40, or 4.18 per cent., were left-handed, and 36, or 3.76 per cent., were ambide* trous, or stated themselves to be so.

. These figures, I have no doubt, place the proportion of the left-handed and ambidextrous too high. I found that my distributors naturally thought more of their interesting left-handed acquaintances than of the commonplace right-handed ones.

As a control observation 1 got my friend Dr. Charles Mayhew to examine the prisoners in' Pentonville prison, certainly not a selected group,1 with reference to this inquiry,' and he found that of 975 prisoners just 24, or about 2J per -cent., were left-handed, no ambidexterity being noted, although one might have thought that a convenient accomplishment for the pickpockets at any rate.

These cases are really instances of natural left-handedness modified by education, but there are cases of genuine and permanent ambidexterity, notably that of Lord Baden-Powell, that benefactor of his country, who is accustomed to use both hands interchangeably, can mount with equal ease on either side.of his horse, wield sword, pistol, and lance. equally well with both hands and arms, shoot off the left shoulder as rapidly and efficiently as from the right,1 and specimens of whose right- and left-hand writing are absolutely undistinguishable from each other. - . - , .

There is no body of men who have more diligently cultivated ambidexterity than the surgeons, for in some of their work, especially that of the opthalmic surgeon, it would be of great'utility to have two right hands. Many of them have attained to remarkable proficiency in the ambidextral handling of surgical instruments, but few if any cf them practise ambidexterity outside the operating theatre.

There is a suspicion that ambidexterity may sometimes be a drawback to a surgeon.' That accomplished'surgeon, the late Mr. John Duncan, of Edinburgh, told me that the only surgeon he knew to be ambidextrous was G., and of him he said: "He is so in all manual actions as far as surgery is concerned, and it is, I think, rather an embarrassment to him as he seems always uncertain which band he had better use." That is a pregnant remark, for the result of a general and systematic ambidextral training, if such a thing were possible, would probably be to reduce those submitted to it to a state of wobble. It has never been suggested that left-handedness or ambidexterity is in« dicative of any mental defect or incompatible with the highest intellectual power or with genius. ' Leonardo da Vinci was left-handed Natural left-handedness is merely a transference of power from' one sic* to the other, and acquired ambidexterity means the special training of certain groups of muscles and their springs in the brain for certain movements. It is all a matter of cerebral organisation. The two hemispheres of the brain are not functionally symmetrical. In a vast majority of persons the left hemisphere is the more voluntary, the right the more automatic, but there, ii an occasional reversal of this arrange* meat. We know now that damage of a certain convolution known as Broca's convolution in the left hemisphere of the brain deprives the right-handed man of speech, but leaves the, left, handed man with speech unimpaired, while damage of the same convolution in the right hemisphere deprives the left-handed man of speech, and leaves the right-handed man with speech intact. Now the hand and arm centres are adjacent to each other and . closely linked with the speech centres in the brain, and it is a significant fact observed oy the London school doctors that stammering is among the nervous symptoms induced by illjudged efforts to correct left-handed-ness in young children in whom the evolutions of the brain centres are still going on. We do not know why there-Is any functional differentiation-in the two hemispheres of the brain, or why in a few instances the prevailing order oC things should be reversed. . The.one* sidedness<of the brain, is a mystery, but it is a mystery that involves the organic world as a whole. We have right- and left-handedness everywhere. In the human subject it is well to accept it as It is, and make the best of it without attempting any futile,. perhaps hazardous, transformation. -- And we should be grateful to the London school doctors..'for. their wise warnings. .