According to Roth (1964), the term "psychopharmakon" was used for the first time by Reinhardus Lorichius of Hadamar who, in 1548, edited a collection of prayers of comfort and in preparation for death under the title "Psychopharmakon, hoc est: medicina animae". With the introduction of chlorpromazine in 1952, the era of psychopharma- cology began. The "psychopharmakon" of the Renaissance and the twentieth century differ from each other in concept and meaning; the spiritual support in times of increased anxiety and fear has been replaced by drugs which "tranquilize" the agitated and brighten the mood of the depressed. Thus, the pioneering discovery by Delay et al. (1952) of the usefulness of phenothiazines in schizophrenics, followed by the report of Loomer et al. (1957) on the antidepressant effect of iproniazid and Kuhn's (1957) observation of the thymoleptic property of imipramine triggered a revolution in psychiatry. Subsequently, numerous new psychopharmaka have been introduced. Parallel with this development, the interest in experimental behavioral research which began to utilize the newly discovered drugs as tools grew rapidly. The experience gained from studies of human and animal behavior found expression in the attempt to introduce a nomenclature and classify psychopharmaka on a purely psychological basis.