The inspiration for the attempt to summarize the results of previous pharmacopsychological and pharmacopsychopathological research in a kind of outline of this science concerning the effects of drugs and toxins on the psyche is owed to the Heidelberg psychologist Professor Dr. Willy Hellpach, who passed away in July 1955. When I asked him in 1948 about relevant publications for a paper on levitation phenomena in connection with literature studies, it soon became clear how laborious it was to find the scattered references in various publication outlets. Furthermore, it turned out that a comprehensive presentation of the subject—aside from the predominantly pharmacologically-toxicologically oriented books by E. Hesse, L. Lewin, K. O. Möller, V. A. Reko, and others—was not available, and one usually does not find it in psychology textbooks either.