and hammer in either hand, and thereby not only resting his arm, but greatly facilitating his work. In all the fine arts the mastery of both hands is advantageous. The sculptor, the carver, the draftsman, the engraver, and cameo-cutter, each has recourse at times to the left hand for special manipulative dexterity; the pianist depends little less on the left hand than the right; and as for the organist, with the numerous pedals and stops of the modern grand organ, a quadrumanous musician would still find reason to envy the ampler scope which a Briareus could command. On the other hand, it is no less true that, while the experience of every thoroughly left-handed person shows the possibility of training both hands to a capacity for responding to the mind with promptness and skill: at the same time it is apparent that in cases of true left-handedness there is an organic specialisation which no enforced habit can wholly supersede. Having determinately arrived at the conclusion that the source of right-handedness, and so of the exceptional occurrence of left-handedness, is to be sought for in the preponderant development of one or other hemisphere of the brain, and that, therefore, the test has to be sought in the examination of the brains of persons of exceptional dexterity, whether in the use of their right or left hand, the difficulty has been to obtain the desired objects of study. A considerable number of observations are desirable; and those can only be gradually accumulated as opportunities present themselves to observant students. As already noted, men of the first eminence have differed on the question of the greater weight of the left than of the right cerebral hemisphere; nor does a study of the ordinary manifestations of right-handedness encourage us to expect a very marked difference in the cerebral hemispheres in the majority of men. It need not therefore surprise us to find so able and experienced an observer as Dr. Thurnam reviewing the data published by Boyd, Brown-Sequard, and Broca, and expressing as his final conviction that further careful observations are needed before the general preponderance of the left hemisphere over the right can be accepted as an established truth.