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Page:Popular Science Monthly Volume 65.djvu/373

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369
DEXTRALITY AND SINISTRALITY.

Almost the only letters that could not he thus remodeled and bettered are V, Z, X, which are little used. K and R also require some slanted strokes. The others could all be made up of vertical and horizontal lines. The vast majority of astigmatisms cluster about axes 90° or 180°, and those which are anomalous and unsymmetric produce disease unless corrected, as they may be by proper spectacles.

The summary of the foregoing theory of the origin of dextralitv and sinistrality is:

Modern pathology has demonstrated that the intellectual acts of writing and reading locate the speech center upon the cerebral side opposite the writing hand.

The centers for vision, audition, and motion of the hand and foot for correlated dextral or sinistral actions and sensations, are in the same side of the brain.

Coordination of sensation, perception, judgment and act are rendered more accurate, expert and quick by this close contiguity and inter-relationship than if made by commissural fibers from the other cerebral hemisphere.

The original location of the speech center in the dextral was caused by the almost universal employment of the right or spear-hand in sign-language preferred to the left or shield-hand, because this was more restricted in movement by holding the shield over the heart.

The origin of left-handedness was in large measure due to the location or education of the speech center in the right brain because of injury to dextral organs, but chiefly to disease or deficient vision of the right eye.

Ambidexterity of any general or thoroughgoing kind is neither possible nor desirable, and the attempt to bring it about results in suffering and disease.

Vertical handwriting, and printed letters made up of vertical and horizontal lines, should be encouraged.