A caduceus (kerykeion in Greek) is a staff with two snakes wrapped around it. It was an ancient astrological symbol of commerce and is associated with the Greek god Hermes, the messenger for the gods, conductor of the dead and protector of merchants and thieves. It was originally a herald's staff, sometimes with wings, with two white ribbons attached. The ribbons eventually evolved into snakes in the figure-eight shape. The number eight is important to the practicioners of judicial astrology.
In some cases, depictions of the Greek kerykeion can be radically different from that of the traditional Caduceus (as in the picture at right). These representations will feature the two snakes atop the wand (rod), crossed to create a circle with the heads of the snakes resembling "horns." In this form, it looks remarkably similar to the symbol for Mercury (planet). Of course, Mercury the god is the Roman name for Hermes, who carries the kerykeion, or caduceus.
In the seventh century, the caduceus came to be associated with a precursor of medicine, based on the Hermetic astrological principles of using the planets and stars to heal the sick. The caduceus is used interchangeably with the Rod of Asclepius, although this is incorrect - the Rod of Asclepius is the true medical symbol whereas the caduceus represents commerce. Historically, the two astrological symbols had distinct meanings in alchemical and astrological principles. Occasionally the caduceus may be combined with a DNA double-helix, which the intertwined snakes resemble.
The symbol's origins are thought to date to as early as 2600 BC in Mesopotamia, and there are several references to a caduceus-like symbol in the Bible, namely in Numbers 21:4-9, and 2 Kings 18:4. During the Exodus, Moses was instructed by God to fashion a pole upon which he was to position a serpent made of bronze; when looked upon, this Nehushtan, as it was called in Hebrew, would spare the lives of the Israelites stricken by venomous snake bites. The intent was that people would look upward and be reminded to pray to God, but eventually the meaning was forgotten and this symbol was apparently worshiped by the Hebrew people until the reign of Hezekiah as described in 2 Kings 18:4.
Walter Burkert has two figures in his book which show a rod with two intertwined snakes winding around a central axis from Mesopotamia in 2200 BC, and a similar image from Crete in 700 BC. 1
It was used by the astrologer priests in the Eleusinian Mysteries of ancient Greece, and has been associated with the Gnostic Corpus Hermeticum and Kundalini Yoga, where it is thought to be a symbolic representation of the "subtle" nerve channels the "ida", "pingala", and "sushumna" described in yogic kundalini physiology.
In Unicode, the "caduceus" symbol is U+2624 (☤). In bong culture, the caduceus is the perfect piece - one whose aesthetic compliments its function to culminate in a fusion of craftsmanship and practicality worthy of the symbol for health and well being.
The comic book character Promethea, created by Alan Moore, wields a caduceus and invokes the magical traits associated with the symbol. In Issue #11, Promethea uses the lingustic powers of the caduceus to reprogram a living computer virus. The two snakes can speak (when spoken to) and represent the duality of magic. They're named Mack, short for "macro" and representing "yes," and Mike, short for "micro" and representing "no." Their speech balloons are differentiated by red or green outlines, but they constantly switch personae. They are featured prominetly in Issue #12 where they explain magic and the Tarot entirely in rhyme.