The widely differing opinions which have been entertained by the ablest physicians respecting the pathology of insanity, clearly shew that there is some difficulty at the bottom of the question, greater than that which has existed with regard to the nature of other classes of disease. The source of this difficulty is not hard to find. A rational pathology must ever be founded upon the basis of physiology. It is indeed a kind of physiology; it is an account of the abnormalities of organization and of function, which as much depend on the natural laws of our being as do those of health. Fair weather and foul equally depend upon the laws of meteorology; health and disease equally depend upon the laws of animal life. The division of their study into the two departments of pathology and physiology is, therefore, perfectly arbitrary, and useful only for purposes of classification. But the knowledge of the laws of aberration cannot precede, or even be contemporaneous with, the knowledge of the normal laws of action. The high-road of health must be well known before the bye-ways and devious paths which surround it can be investigated.