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.
The Worship of the Serpent worship, not just confined to Europe, but indeed all over the world. Deane goes on in his title to list a number of associations to the serpent such as the dragon and the leviathan. So thorough (albeit outdated) is his research, that he has "traced THE WORSHIP OF THE SERPENT from Babylonia, east and west, through Persia, Hindûstan, China, Mexico, Britain, Scandinavia, Italy, Illyricum, Thrace, Greece, Asia Minor, and Phœnicia." (Ch VIII) The Worship of the Serpent The Worship of the Serpent by John Bathurst Deane is an 1833 study of snake worship and specifically the snake mentioned in the