Many theories as to the origin of handedness have been formulated. It has been argued that handedness is not innate, but acquired from the mother’s habitual method of carrying the infant on one arm rather than on the other, so that one of its arms is pinioned against the mother habitually, and gets comparatively little exercise. The theory has been advanced that since the heart is the most vital organ of the body, and is located on the left side, the shield to protect it was held by the left hand, permitting the right hand to attain greater dexterity with the spear, the advantage thus acquired being transmitted to offspring. Also, it has been proposed that the center of gravity of the viscera, the position of the subclavian arteries, cerebral asymmetry, and greater blood supply to one cerebral hemisphere may be, respectively, the origin of handedness. All of these theories are unsatisfactory, for reasons which have been well stated by the original investigators. There remains to be considered the proposal that handedness is determined by ocular dominance. The right eye is the better seeing eye in about 96 per cent of people. As vision develops long before muscular coördination in the infant, the proposal is that the hand is brought to coöperate with the dominant eye. The disproof of this theory is that among the congenitally blind the proportion of right-handed to left-handed is not materially different from that among seeing persons. The origin of handedness is, therefore, not understood, and it is not known why about 4 per cent of the population should show dominance of the left hand. It must be considered that handedness is of many degrees, from extreme right-handedness, through ambidexterity, to extreme left-handedness. All right-handed persons are not equally right-handed, and all left-handed persons are not equally left-handed. Trustworthy studies of the heredity of handedness indicate that it is inherited. Ramaley studied 610 parents and 1130 children, and arrived at the conclusion that left-handedness is inherited (as a Mendelian recessive), and is potential in about one-sixth of the population. It is obvious that modern appliances are adapted to the right-handed, and that right-handedness is regarded generally as “the way to be.” Teachers and parents feel it their duty to compel the child to use the right hand.