Ahriman is of the darkness, and from this emanate Daêvas, powers by whom mankind are led to their destruction—evil powers, false gods, devils. From these Daêvas proceed all the evil which is in the world; they are agents of that higher evil principle Druj, or falsehood and deception, which is called Ahriman, the spirit enemy. These Daêvas send to men, and are the causes of all diseases, which can only be cured by the good spirits. Man belongs either to Ormuzd or to Ahriman according to his deeds. If he offers sacrifice to Ormuzd and the gods, and helps them by good thoughts, good deeds, and spreads life over the world and opposes Ahriman by destroying evil, then he is a man of Asha, who drives away fiends and diseases by spells. He who does the contrary to this is a Dravant,—“demon,” a foe of Asha. The man of Ormuzd will have a seat near him in heaven.[320] According to the _Zend-Avesta_ Thrita was the first physician who drove back death and disease. Ormuzd (Ahura Mazda) brought him down from heaven ten thousand healing plants which had grown around the tree of eternal life, which is the white Haoma (the Indian Soma), or Gaokerena, which grows in the middle of the sea, Vouru-kasha. These are the Haomas, says Darmesteter.[321] One is the yellow, or earthly Haoma, and is the king of healing-plants; the other, or white, is that which, on the day of resurrection, will make men immortal. Thrita was one of the first priests of Haoma, the life and health-giving plant, and thus he obtained his skill in medicine. Darmesteter says that Thrita was originally the same as Thraêtaona of the _Rig-Veda_.[322] “We see that Thraêtaona fulfilled the same functions as Thrita. According to Hamza he was the inventor of medicine. The Tavids (formulas of exorcism) against sickness are inscribed with his name, and we find in the Avesta itself the Fravashi of Thraêtaona invoked ‘against itch, hot fever, humours, cold fever, vâvareshi; against the plagues created by the serpent.’ We learn from this passage that disease was understood as coming from the serpent; in other words, that it was considered a sort of poisoning, and this is the reason why the killer of the serpent was invoked to act against it. Thus Thrita Thraêtaona had a double right to the title of the first of the healers, both as a priest of Haoma and as the conqueror of the serpent.”