The Caduceus of Mercury (Roman) and
the Karykeion of Hermes (Greek)
Many "medical" organizations use a symbol of a short rod entwined by two snakes and topped by a pair of wings, which is actually the caduceus or magic wand of the Greek god Hermes (Roman Mercury), messenger of the gods, inventor of (magical) incantations, conductor of the dead and protector of merchants and thieves. It is derived from the Greek karykeion = "herald's staff", itself based on the word "eruko" meaning restrain, control.
It is interesting to see that most of organizations using this symbol are generally either commercial or military (or American). New Zealand examples include drug and pharmaceutical companies. A study by Friedlander confirms this impression.