A well-known author has said that the difference between sanity and insanity depends only on the power to conceal the emotions. While this definition will hardly pass in law or medicine, it surely offers food for thought. Suppose for a moment that we were dominated by the impulse to externalize all our thoughts and all our emotions, there would be some basis for the common, but inaccurate, saying that everyone is insane. This brings us to a form of insanity which the obsessive may well bear in mind, namely, that known as manic-depressive. This disorder, in its typical form, is shown by recurring outbursts of uncontrollable mental and physical activity (mania), alternating with attacks of profound depression (melancholia). This form of insanity represents the inability to control an extreme degree of the varied moods to which we all are subject. Long before the modern classification of mental disorders, Burton, in his introduction to the "Anatomy of Melancholy," expressed this alternation of moods thus: "When I go musing all alone, Thinking of divers things foreknown, When I build castles in the ayr, Void of sorrow and void of feare, Pleasing myself with phantasms sweet, Me thinks the time runs very fleet. All my joyes to this are folly, Naught so sweet as melancholy. "When I lie waking all alone, Recounting what I have ill done, My thoughts on me they tyrannize, Feare and sorrow me surprise, Whether I tarry still or go, Me thinks the time moves very slow. All my griefs to this are jolly, Naught so sad as melancholy." * * * * * "I'll not change my life with any King, I ravisht am: can the world bring More joy, than still to laugh and smile, In pleasant toyes time to beguile? Do not, O do not trouble me, So sweet content I feel and see. All my joyes to this are folly, None so divine as melancholy. "I'll change my state with any wretch Thou canst from goale or dunghill fetch: My pain's past cure, another hell, I may not in this torment dwell, Now desperate I hate my life, Lend me a halter or a knife; All my griefs to this are jolly, None so damn'd as melancholy." The depressed stage of this disorder is commonly shown by retardation of thought and motion, the excited stage by pressure of activity and acceleration of thought. In the so-called "flight of ideas" words succeed each other with incredible rapidity, without goal idea, but each word suggesting the next by sound or other association, thus: "Are you blue?" "Blue, true blue, red white and blue, one flag and one nation, one kingdom, one king, no not one king, one president, we are going to have a president first, cursed, the worst."