Although we have, for some time past, begun to emancipate ourselves from the idea that insanity is a disease of the mind, and admit, in theory at least, that it is strictly a disease of the body, as much so as typhus, or any other disease involving perturbed mental phenomena, yet we have scarcely hitherto begun to investigate the pathology of insanity from this point of view. Even yet we classify the forms of the disease by the mental manifestations it presents, and speak of mania, melancholia, dementia, &c., when our aim ought to be to differentiate the physical or chemico-vital somatic conditions; we describe the insanity of fear, of pride, of exaltation, &c., much as if we should classify ulcers as those of the hand, the arm, the leg, and the trunk, instead of attending to the more important characters of ulcers in general with their true specific differences. For, I venture to think, that Professor Ferrier's researches point strongly to the view that the differences in direction, so to speak, taken by the mental phenomena depend to a great extent upon the differences in the portion of brain-tissue principally affected. The investigation of the physical causation and conditions of insanity will doubtless be laborious and tedious work, but there can be no doubt that the results to be obtained will more than repay the labour which must be expended in the investigation.