INTRODUCTION
From the clinical point of view, left-handedness is usually regarded as an insignificant physical peculiarity. Various authors, it is true, point out that this affection may have a background of psychomotor symptoms, but such statements seem to have attracted very little attention. In 1870, Cooke1 declared his belief that all left-handed persons are "more or less `odd,'" and this is probably a fair expression of current opinion on the subject today. It does not appear to be generally known that in addition to a simple form, there are crossed forms of left-handedness or sinistrality. The simple, familiar form may reveal itself in an individual through some deviation from the right-handed conventions. On the other hand, the crossed forms are latent and unless they are sought for they escape observation. Left-eyedness, for example, is not uncommon in the right-handed and, conversely, righteyedness is common in sinistrals. The etiology of these