Caduceus is a continuation of the older Indo-European dragon-slayer motif. Wilhelm Heinrich Roscher (1913) pointed out that the serpent as an attribute of both Hermes and Asclepius is a variant of the "pre-historic semi-chthonic serpent hero known at Delphi as Python", who in classical mythology is slain by Apollo. One Greek myth of origin of the caduceus is part of the story of Tiresias, who found two snakes copulating and killed the female with his staff. Tiresias was immediately turned into a woman, and so remained until he was able to repeat the act with the male snake seven years later.
Snake worship the sky as the constellation Ophiucus, "the Serpent-Bearer". The modern symbol of medicine is the rod of Asclepius, a snake twining around a staff, while the symbol of pharmacy is the bowl of Hygieia, a snake twining around a cup or bowl. Hygieia was a daughter of Asclepius. Laocoön was allegedly a priest of Poseidon (or of Apollo, by some accounts) at Troy; he was famous for warning the Trojans in vain against accepting the Trojan Horse from the Greeks, and for his subsequent divine execution. Poseidon (some say Athena), who was supporting the Greeks, subsequently sent sea-serpents to strangle