The Caduceus and the Rod of Asclepius

 The caduceus (☤; /kəˈdjuːʃəs, -siəs/; Latin: cādūceus, from Greek: κηρύκειον kērū́keion "herald's wand, or staff") is the staff carried by Hermes in Greek mythology and consequently by Hermes Trismegistus in Greco-Egyptian mythology. The same staff was borne by other heralds like Iris, the messenger of Hera. The short staff is entwined by two serpents, sometimes surmounted by wings. In Roman iconography, it was depicted being carried in the left hand of Mercury, the messenger of the gods.

Some accounts assert that the oldest imagery of the caduceus is rooted in Mesopotamia with the Sumerian god Ningishzida; his symbol, a staff with two snakes intertwined around it, dates back to 4000 BC to 3000 BC.

As a symbol, it represents Hermes (or the Roman Mercury), and by extension trades, occupations, or undertakings associated with the god. In later Antiquity, the caduceus provided the basis for the astronomical symbol for the planet Mercury. Thus, through its use in astrology, alchemy, and astronomy it has come to denote the planet Mercury and by extension the eponymous planetary metal. It is said that the wand would wake the sleeping and send the awake to sleep. If applied to the dying, their death was gentle; if applied to the dead, they returned to life.

By extension of its association with Mercury and Hermes, the caduceus is also a symbol of commerce and negotiation, two realms in which exchange balanced by reciprocity is recognized as an ideal. This association is ancient and consistent from classical antiquity to modernity. The caduceus is also a symbol of printing, by extension of the attributes of Mercury associated with writing and eloquence.

Although the Rod of Asclepius, which has only one snake and no wings, is the traditional and more widely used symbol of medicine, the Caduceus is sometimes used by healthcare organizations. Given that the caduceus is primarily a symbol of commerce and other non-medical symbology, many healthcare professionals disapprove of this use.

***In Greek mythology, the Rod of Asclepius (⚕; Ancient Greek: Ῥάβδος τοῦ Ἀσκληπιοῦ, Rhábdos toû Asklēpioû, sometimes also spelled Asklepios), also known as the Staff of Aesculapius and as the asklepian, is a serpent-entwined rod wielded by the Greek god Asclepius, a deity associated with healing and medicine. In modern times, it is the predominant symbol for medicine and health care, although it is sometimes confused with the similar caduceus, which has two snakes.