In those and similar cases, the fact is illustrated that the left-handed person is necessarily ambidextrous. He has the exceptional “dexterity” resulting from the special organic aptitude of the left hand, which is only paralleled in those cases of true right-handedness where a corresponding organic aptitude is innate. Education, enforced by the usage of the majority, begets for him the training of the other and less facile hand; while by an unwise neglect the majority of mankind are content to leave the left hand as an untrained and merely supplementary organ. From the days of the seven hundred chosen men of the tribe of Benjamin, the left-handed have been noted for their skill; and this has been repeatedly manifested by artists. Foremost among such stands Leonardo da Vinci, skilled as musician, painter, and mathematician, and accomplished in all the manly sports of his age. Hans Holbein, Mozzo of Antwerp, Amico Aspertino, and Ludovico Cangiago, were all left-handed, though the two latter are described as working equally well with both hands. In all the fine arts the mastery of both hands is advantageous; and accordingly the left-handed artist, with his congenital skill and his cultivated dexterity, has the advantage of his right-handed rival, instead of, as is frequently assumed, starting at a disadvantage. CHAPTER X CONFLICT OF THEORIES It now remains to consider the source to which the preferential use of the right hand is to be ascribed. The dominant influence of the one cerebral hemisphere in relation to the discharge of nerve force to the opposite side of the body is a fact which is now familiar to the physiologist, and the influence of the left cerebral hemisphere on the action of the right hand has already been alluded to. But this extremely probable source of right-handedness long eluded inquirers, as will be seen from a _résumé_ of the various hypotheses suggested by eminent anatomists and physiologists. A very slight consideration of the evidence already adduced in proof of the same prevalent usage from earliest times precludes the idea of its origin in any mere prescribed custom, enforced and developed by education into a nearly universal habit. This becomes the more manifest when it is traced back to primæval races; found incorporated in ancient and modern, savage and civilised languages, and uncontroverted by any evidence calculated to discredit the indications that it was a characteristic of palæolithic and neolithic man.