Page:Popular Science Monthly Volume 65.djvu/366

362 man; (2) in the secondary meaning of the word sinister—unlucky, ill-omened, evil; (3) in the persistent training of all left-handed children, by parents, teachers, etc., to make them like the rest of the right-handed world. These three facts, the residue of the psychologic habits of ages, persistent in all history, crystallized and embedded in the very language itself which chronicles all mentality, help to give us the clue to the solution of the riddle.

Skillfulness, 'handiness,' expertness of sense and act, were the sole means whereby the savage could win his place in the world, domesticate animals, conquer in all sorts of conflicts, supply himself with food, clothing, house, etc. It was necessary that one hand should be chosen to do the dextrous or more skilled tasks, for the simple reason that exercise develops and perfects function, and one would learn to be more skilled and 'handy' with one hand than with both. The savage required no treatise on logic nor even any conscious reasoning to teach him this primary lesson. His food and life depended upon his learning it.

But that it was an acquirement, that the law and necessity were not exceptionless, that it was due to no absolute fatalism of anatomy or physiology, is evident from the fact that so large a proportion of left-handed children and adults exist in all races and times. The education of left-handed children, whereby their writing center, naturally dextrocerebral, is by forced training and long habit transferred to the left cerebral hemisphere, is another demonstration that no inherent neurologic or psychologic law governs the location of the cerebral center or its peripheral outworking. When the occasions arose in the humanization process, and the demand for the differentiation of cerebral mechanisms was made, the plastic brain on either side could take up the work. And pure, or untrained, left-handed persons are to-day as expert as their right-handed fellows. All that is needed to explain dextrality in 98 per cent, of children is some ancestral savage custom, habit, or necessity, widely prevalent, which inclined to the use of the right hand and eye for one or two exceptionally intellectual tasks. The inheritance of aptitude, the force of custom, and the necessities of the struggle for existence would certainly fix the persistence of dextrality.

We must not forget that the somewhat sudden and clear preference of dextrality and sinistrality of the child of to-day was in the far-away ancestral line spread out over long periods of time. A year or two of the child's life represents thousands of years of slow acquirement and habit.

Again, it should be remembered that even in our preferences and habits it is only in a few things that one hand, etc., has the greater expertness, accuracy and rapidity. It is often rather a division of