use of either hand, that many brains should come under the notice of careful observers where little or no difference can be found between the two hemispheres. But weight is not the only element of variation. Dr. Bastian, in _The Brain as an Organ of Mind_, draws attention to the unsymmetrical development of the two hemispheres as one of the most notable peculiarities of the human cerebrum. This is not only the case with reference to the number and arrangement of the convolutions, but it has been noted by various anatomists that the left hemisphere is very frequently slightly longer than its fellow. But interesting light has been thrown by pathological observations on the comparative relations of the cerebral hemispheres; and in this more than in any other direction we may look for further elucidation. As already noted, Sir Charles Bell affirms a general inferiority in muscular strength and in vital properties of the left side of the body, and a greater liability to disease in the left extremities than the right. On the other hand, Dr. O’Connor refers a greater susceptibility to disease of the left hemisphere of the brain to what he assumes as the source of superior vital force. Having assigned the causes of greater development as already cited, he proceeds to affirm that “the greater directness of communication between the heart and left hemisphere explains the greater readiness with which the latter is subjected to certain forms of disease. A clot of fibrine whipped off a diseased valve is carried much more readily because of the direct route (_viâ_ the carotid) to the left hemisphere; and in conditions of degenerative weakness of the arteries in general, those of the left hemisphere being subjected to greater pressure in their distal ramifications, will be more apt to yield than corresponding ones in the right.”