The _immediate cause_ of nightmare is undoubtedly the circulation of blood through the brain which has not been sufficiently aerated. The appearance of the sufferer is sufficient to indicate this, as the condition of the cerebral vessels and all the exciting causes act either by retarding the flow of the venous blood from the brain, or by impeding the respiratory movements. The effects of emotion, of mental fatigue, and of severe and long-continued muscular exertion are such that the nervous influence to the muscles of respiration is increased, or the muscles themselves are debilitated through this general fatigue of the organism. Fullness of the stomach acts mechanically, by interfering with the action of the diaphragm, and constriction about the neck directly increases the flow of blood through the brain. Certain diseases of the heart and lungs act upon the function of respiration, and thus interfere with the due oxygenation of the blood. The _treatment_ of morbid dreams presents no points of any difficulty. When they are the result of impressions made during sleep upon the nerves, and are the forerunners of disease, it is not very likely that physicians will be consulted as to their cure. Undoubtedly, however, much can be done to abate them when they belong to the category of prodromic dreams, as well as when they are symptomatic of existing disease. Hygienic measures, such as open-air exercise, attention to diet, and warm baths, and the use of the oxide of zinc and bromide of potassium, will do much to lessen the irritability of the nervous system, and to diminish any hyperæmic condition of the brain. Nightmare often requires more active management, though even here we will ordinarily find the measures above mentioned the most effectual that can be taken for its treatment. Of course the exciting cause must be ascertained if possible, and means taken to remove it. This is not always an easy matter, and frequently cannot be accomplished without a considerable alteration in the course of life followed by the patient, and more or less sacrifice on his part. Among hygienic measures, I have several times found relief follow a sojourn at the sea-shore, and ocean bathing. Change of air is almost invariably beneficial, and moderate physical exercise, just to the point of fatigue, can scarcely be dispensed with. A gentleman, at this moment under my care, has been cured by a course of gymnastic training, which he took at my instance. The food of those subject to nightmare should always be plain, easily digestible, and moderate in quantity. Alcoholic beverages should always be sparingly taken, especially just before going to bed. Any article of food or drink known to produce the paroxysm, should of course be omitted altogether.