SLEEP.--The number of hours a patient sleeps should be noticed and recorded as accurately as possible. The word of the patient on this subject is not sufficient evidence. Character of sleep should also be noted, whether it is quiet or restless, and whether the patient sleeps lightly or is difficult to arouse. MENTAL CONDITIONS.--It is important to watch carefully the mental condition of a patient; whether, for example, he is normal, or depressed, irritable, restless, apathetic, dull, excited, wandering, delirious, or unconscious. Hasty judgment of mental conditions should be avoided, but close attention to them is necessary. SUBJECTIVE SYMPTOMS PAIN is the most important subjective symptom and should never be disregarded. Bodily pain does not occur in persons who are in all regards physically and mentally well; hence pain is a sign that something, small or great, is out of order. "Of all symptoms pain is the one which interests patients the most. We here emphasize the truth, too little understood, that pain is an unpleasant sensation, nothing more, and is _never_ imagined. Imagination may be its cause, but the pain thus produced hurts just as truly as pain produced by a real disease. Pain is only a phenomenon of consciousness; it is always real, even that felt in a dream. If the patient is too unconscious to feel it, there simply is no pain, no matter how badly the person's body is injured." (Emerson: Essentials of Medicine, p. 356.) One should remember that no possible method exists to measure the intensity of pain exactly, or to describe its quality accurately. Therefore in describing pain, it is best to use the patient's own language. Four points should especially be observed, (1) its location; (2) its character, which may be dull or sharp, stabbing, throbbing or continuous, slight or severe; (3) the time at which it is worst; certain diseases, for instance, are characterized by more severe pain at night; (4) it should be noticed whether the pain is relieved or increased by change of position, eating or drinking, heat or cold, or the like. Pain may be felt in a part far from the place where the trouble really lies; thus a dislocated shoulder causes pain in the elbow.