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Page:Popular Science Monthly Volume 65.djvu/367

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363
DEXTRALITY AND SINISTRALITY.

functions, a differentiation of ability, than a unique one. In the dextral the left hand does many tasks of as great or greater importance, and with equal or superior skill, as the right. In eating, the fork is now more used than the knife; in gunning, the left hand is given the vastly more important, difficult and onerous task; in chopping, hoeing, shoveling, picking, lathe-work, railway locomotive engineering and other tasks the left arm and hand often execute the chief and more expert tasks. Especially noteworthy is the playing of the violin, 'cello and bass viol. The 'fingering' is done with the left hand, and forms a striking reversal of dextrality, because it is hy all odds the function requiring more manipulative skill, accuracy and rapidity. I do not know that the fact itself has ever been observed and stated, but certainly the reason of this strange contradictory practise has hitherto escaped the attention. It is, I think, due to dextrocularity. With few and easily explained exceptions dextromanuality is a result, or a concomitant, of dextrocularity. If the violin, 'cello and viol were fingered with the right hand the learner would be greatly handicapped by the foreshortening which would exist as his dextral eye glanced along the neck of the instrument straight in front or below this eye. The learner must see his fingers and gain precision in placing them by careful visual estimates. But when placed sinistrad the right eye sees the neck of these instruments and the fingers at an angle which permits more accurate observation, estimates of distances, etc., than would be possible if the instrument were fingered with the right hand. In those instruments necessarily held in the median line, some wind-instruments, the flageolet, hautboy, etc., the right hand asserts its selective and more difficult task. When the hands are not seen at all, as in the flute, fife, etc., the right again has its choice. No pupil with sinistromamiality established can learn piano-playing easily. I know of one who was a great lover of music who failed utterly after long perseverance.

There are other cautions to be emphasized relating to the acquirement of dextrality by the savage: Nearly all the actions which we now call right-handed were in primeval times to him unknown. This is especially true of three things. Knives and forks have only been used in eating for a few hundred years. He ate with his fingers, and one may suspect he used the left as much as the right in this way. The Mussulman custom and its reason are, of course, both modern. Secondly, the modern gun and revolver had not been devised. The bow and arrow, the spear, boomerang, club, etc., could be used as well with the left hand by the sinistromanual. Thirdly, writing was unknown, or relatively so, and, as we have now learned, that locates the speech center in the cerebral hemisphere opposite the writing hand. It is thus evident that dextrality in the savage, at the time when it