Only in "Maria" and in "Aebelö" however do these themes play an important part, while in the other works mentioned they serve properly only as adornment and episodic ornament. I am not able to explain this unusual restraint, unless we accept the fact that our best poets shrink from touching upon questions which they themselves can so little understand. It has been expected that the psychoanalytic method, which casts such light upon the unconscious, might do much to advance the understanding of the problems of sleep walking and moon walking. But unfortunately no one undergoes such an expensive and time-consuming treatment as psychoanalysis for moon walking, so that the hoped for illumination can come at the best only as a by-product in the psychoanalysis of neurotics. That has in fact been my good fortune twice, where I have been able to lift the curtain, though only a little, in two cases among my patients and also in individuals who were otherwise healthy. What I discovered there, I will relate in detail in what follows. One point of view I will first set forth. Two questions appear to me to stand out among those closely bound with our theme. First on the motor side. Why does not the sleep walker, who is enjoying apparently a specially deep slumber, sleep on quietly and work out the complexes of his unconscious somehow in a dream, even though with speech or movement there? Why instead is he urged forth and driven to wander about and engage in all sorts of complicated acts? It is one of the most important functions of the dream to prolong sleep quietly. And then in the second place, What value and significance must be attributed to the moon and its light? These two chief questions must be answered by any theory that would do justice to the question of sleep walking and moon walking. PART I Medical CASE I. Some years ago I treated a hysterical patient, exceedingly erotic. She was at that time twenty-two years old, and on her father's as well as on the mother's side, from a very degenerate family. Alcoholism and epilepsy could be traced with certainty to the third ascendant on both sides. The father's sister is mentally diseased, the patient's mother was an enuretic in her earlier years and a sleep walker. This mother, like her father when he was drunk, was markedly cruel and given to blows, characteristics, which according to our patient, sometimes almost deprived her of her senses and in her anger bordered upon frenzy.