Disposition and Digestion.--The relation of the body to the mind in many other besides the purely animal digestive functions has always been realized. It has always been felt that the disposition of an individual depended to a great extent on his nutrition. Men were not usually approached for favors before their meals, and especially after a long fast, but, as far as possible, requests were made shortly after meals. It has always been recognized that the best time for men to get together in council is, at least so far as amiability goes, shortly after meals. Tiredness was also felt to be an important element in affecting the mind. The tired man, even though he may be hungry, can only eat a hearty meal at the risk of serious disturbance of digestion, for, as a consequence of the fatigue of the body being communicated to the mind, the mental influence which predisposes to good digestion is lacking, and it is easy for serious digestive disturbances to be set up. In a word, body and mind are inextricably involved in all that concerns not only health but good feeling, and these two terms are practically convertible. Feeling and Expression.--In nothing is the influence of the body on the mind more clear than in the influence of expression upon the disposition. Actors know that if they want to well express a certain feeling, they must arouse that feeling deeply, and the easiest, surest and most direct method of doing so is to fix the features in the expressions that would ordinarily indicate the presence within of these feelings. If we insist on putting our features into the shape which ordinarily expresses sadness, that will be reflected internally, and we shall become as sad as our expression. On the other hand, if the features are drawn, even by force of will, into the state that ordinarily expresses joy or lightness of heart, we shall be tempted more and more to feel that way, until at last even internal melancholy may be dissipated. In the oldest book in the world, "The Instruction of Ptah Hotep," written about 3,000 years before Christ, the old father giving advice to his sons says: "Let thy face be bright what time thou livest," and the literature of every time since then emphasizes the same idea.