For Biblical imagery related to the caduceus, please see 2 Timothy 3:8-9 (Jannes and Jambres).
The caduceus 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.
The Rod of Asclepius is an ancient Greek symbol associated with astrology and healing the sick with medicine.
Both are now used to represent modern medicine. Friedlander surveyed 242 logos or insignias of American organizations relating to health or medicine in which the caduceus or staff of Asclepius formed an integral part dating from the late 1970s to early 1980s. He found that professional associations were more likely to use the staff of Asclepius (62%) while commercial organizations were more likely to use the caduceus (76%). The exception is for hospitals, where only 37% used a staff of Asclepius versus 63% for the caduceus [but remember that US hospitals are usually commercial ventures]. Friedlander notes that while the prevalent use of the caduceus for the commercial aspects of medicine might be seen as “more-or-less appropriate”, he thinks the reason is that professional associations are more likely to have a real understanding of the two symbols, whereas commercial organizations are more likely to be concerned with the visual impact a symbol will have in selling their products. “Friedlander, Walter J. The Golden Wand of Medicine: A History of the Caduceus Symbol in Medicine.” New York, Greenwood, 1992
The Star of Life is a blue, six-pointed star, outlined with a white border which features the Rod of Asclepius in the center, originally designed and governed by the U.S. National Highway Traffic Safety Administration (NHTSA) (under the United States Department of Transportation, DOT). Traditionally in the United States the logo was used as a stamp of authentication or certification for ambulances or EMS personnel. Internationally, it represents emergency medical services (EMS) units and personnel. A similar orange star is used for search and rescue personnel and yet another version is used for Wilderness emergency medical technician.
The caduceus as a Medical symbol: The link between Hermes and his caduceus and medicine seems to have arisen by Hermes’ links with alchemy. Alchemists were referred to as the sons of Hermes, as Hermetists or Hermeticists and as “practitioners of the hermetic arts”. By the end of the sixteenth century, the study of alchemy included not only medicine and pharmaceuticals but chemistry, mining and metallurgy. Despite learned opinion that it is the single snake staff of Asclepius that is the proper symbol of medicine, many medical groups have adopted the twin serpent caduceus of Hermes or Mercury as a medical symbol during the nineteenth and twentieth centuries.
Reproduced with permission from: www.drblayney.com/Asclepius.html