Caduceus

(Kah-du'seus)

In Mythology, the wand or staff carried by Hermes or Mercury having two serpents entwined around it, and surmounted by two wings. Used as the medical insignia of certain medical groups such as the U.S. Army Medical Corps.
In the United States the Caduceus is the more popular of the two commonly used symbols of medicine. The other symbol is the staff of the Greek and Roman demigod of medicine, Aesculapius. The Caduceus was the magic rod of Hermes, the messenger of the gods. The U.S. Army Medical Corp adopted the official insignia in 1902.
The "Herald's wand" was depicted as a medicinal or magical tool to indicate healing and immortality in literature and drawings from the era before Christ. The fabled wand or rod, the Caduceus, was carried by Hermes and Mercury. It was a symbol of authority and inviolability. It also protected the Herald who carried it.
The earliest Caduei were shaped like a figure eight with the top circle opened up. Snakes were added as early as the 5th century B.C. but remained unusual until the Middle Ages or the early Renaissance period. The wings were later added in the 4th century B.C.