The use of heliotherapy originated with that sage of Kos and high priest of medicine, Hippocrates. A great temple known as the Aesculapion was built on the slope of a mountain. It faced south so as to receive the maximum of sunlight. The temple was dedicated to Aesculapius, and in this institution sun bathing was indulged in. Ancient Egypt appreciated the power of sunlight, and in the fourth dynasty, Ra, the sun, became the "king of the gods." In the eighteenth dynasty, Aton became predominant, which was an entirely different conception of the sun than Ra. Aton, according to Petrie,1was the beneficent sun; its beams imparted life and power to the reigning king. The Romans also made the sun an object of adoration. Cicero mentioned the sun bath, and during his time solaria were popular. Herodotus and Antyllus recommended sun bathing for diseases of the skin. Heliotherapy remained