It was necessary before gaining mastery over the powers of nature to become initiated into the mysteries of Mitra. However, after priestly consecration had once been bestowed, the individual thus honored bore the proud title “Conqueror of Evil,” and was able to practise medicine. As the most essential constituent of every medical treatment, the divine word was applied in the form of mysterious exorcisms, sacred hymns, and certain words which were considered specially curative in effect, particularly the word “Ormuzd,” the name of the highest god, in whose all-embracing power of healing great confidence was placed. The Sumerians, the precursors of Babylonico-Assyrian culture, ascribed a considerable and important rôle to dreams. They were considered to bring direct medical advice from the gods, and it became the office of the sacerdotal physician to interpret the dream in such a way as to alleviate the sufferings of the dreamer. The ancient Greek culture also conceded a conspicuous medical significance to dreams, and even arranged a system of its own, that of the temple sleep, in order always to obtain prophesying dreams from the gods. The patient, after the obligatory offering, was required to remain a night in the temple, and his dream during this night was the medical advice of the divinity in its most direct form. But only the priest was able to interpret a dream obtained in such a manner, and to extract medical efficacy from it. But as it occasionally happened that a too prosaic and phlegmatic patient did not dream at all, the priest was benevolent enough to intercede. He was always promptly favored by the gods with a suggestive dream.