Dr. Brown-Sequard, in one of his latest discussions of the closely related, though much more comprehensive question, “Have we two brains?” remarks: “We have a great many motor elements in our brain and our spinal cord which we absolutely neglect to educate. Such is the case with the elements which serve for the movements of the left hand. Perhaps fathers and mothers will be more ready to develop the natural powers of the left hand of a child, giving it thereby two powerful hands, if they believe, as I do, that the condition of the brain and spinal cord would improve if all their motor and sensitive elements were fully exercised.” Without entering on the discussion of the larger question of the specific duality of the brain, experience shows that wherever the early and persistent cultivation of the full use of both hands has been carried out, the result is greater efficiency, without any counterbalancing defect. Under no enforcement of a violation of his innate impulses does the left-handed person ever exchange hands. He acquires an educated right hand and retains the dexterity of the left. In those cases where, by reason of injury or disease, the sufferer is compelled to resort to the neglected hand even late in life, it proves quite possible to train it to sufficient aptitude for all ordinary requirements. It is therefore obviously the duty of parents and teachers to encourage the habitual use of both hands; and in the case of manifest left-handedness, to content themselves with developing the free use of the right hand without suppressing the innate dexterity of the left. My own experience, as one originally left-handed, is that, in spite of very persistent efforts on the part of teachers to suppress all use of the left hand, I am now thoroughly ambidextrous, though still with the left as the more dexterous hand. I use the pen in the right hand but the pencil in the left; so that, were either hand disabled, the other would be at once available for all needful operations. Yet at the same time the experience of a long life assures me that scarcely any amount of training will suffice to invest the naturally sinister hand, whether it be the right or the left, with the dexterity due to innate, congenital, and therefore ineradicable causes. Nevertheless we are bimanous in the best sense, and are meant to have the free unrestrained use of both hands. In certain arts and professions both hands are necessarily called into play. The skilful surgeon finds an enormous advantage in being able to transfer his instrument from one hand to the other. The dentist has to multiply instruments to make up for the lack of such acquired power. The fencer who can transfer his weapon to the left hand, places his adversary at a disadvantage. The lumberer finds it indispensable in the operations of his woodcraft to learn to chop timber right and left-handed; and the carpenter may be frequently seen using the saw