Caduceus

The caduceus (pronounced from Greek "karykeion," κηρύκειον meaning "herald.")

The caduceus served as the symbol of Hermes and Mercury, the Greek and Roman messenger gods. The caduceus was the sign of a herald and hence a logical symbol for the messenger. However, because of a misconception, the caduceus became the sign of the US Army Medical Corps. The Medical Corps should have chosen the symbol of medicine, which is the rod of Aesculapius , which has only one snake and no wings atop it. No wings were necessary since the essence of medicine is not speed. The single serpent that could shed its skin and emerge in full vigor represents the renewal of youth and health.

The caduceus with its pair of snakes coiled about each other bears some resemblance to the structure of DNA, the double helix, which was only discovered in modern times (in 1953, if that is still in "modern times").