When the affection has lasted a long time, it is more difficult to break up the acquired habit. In these cases, the plan so successfully employed by the daughter of the Spanish officer will almost invariably succeed. Finally, persons subject to nightmare should so train the mind as to employ the intellectual faculties systematically, by engaging in some study requiring their full exercise. The action of the emotions should be as much as possible controlled, and the reading of sensational stories, or hearing sensational plays, should be discouraged. By severe mental training, individuals can do much to regulate the character of their dreams. It is a well-recognized fact, that intense thought upon subjects which require the highest degree of intellectual action is not favorable to the production of dreams of any kind. CHAPTER VII. SOMNAMBULISM. The phenomena exhibited by a person in the condition of somnambulism are so wonderful, that they have from the earliest times excited the superstitious feelings of the ignorant, and claimed the most serious attention of the learned. To see an individual apparently asleep to the greater part of surrounding objects, yet so keenly awake to others as to be able to perform the most intricate actions without the aid of the senses, is so greatly at variance with the common experience of mankind, as to call up feelings of astonishment, and perhaps of awe, in the minds both of the vulgar and those accustomed to scientific investigation. In those times, when the marvelous exercised so powerful an influence over mankind, and when all phenomena out of the ordinary course of everyday life were regarded as supernatural, it was the prevailing belief that the somnambulist was possessed. Modern science has at last dispelled this idea, and though it has not yet been able to furnish a rational theory of somnambulism which will account for all the manifestations of the affection, it has done much toward elucidating the functions of different parts of the nervous system, and thus to prepare our minds for a full understanding of the subject. Somnambulism has been defined[109] as “a condition in which certain senses and faculties are suppressed or rendered thoroughly impassive, while others prevail in most unwonted exaltation; in which an individual, though asleep, feels and acts most energetically, holding an anomalous species of communication with the external world, awake to objects of attention, and most profoundly torpid to things at the time indifferent; a condition respecting which most commonly the patient on awaking retains no recollection; but on any relapse into which, a train of thought and feeling related to and associated with the antecedent paroxysm will very often be developed.”