The staff of Aesculapius represents the modern medical profession. It's an ancient symbol of a knotted wooden staff around which a mystical snake is coiled. In Greek mythology, Aesculapius was revered as a divinely inspired physician and was thought to sometimes appear as a snake. Patients who saw snakes in their dreams believed that the God of healing had come to their aid.
Not to be confused with the Caduceus, used by some Military Medical Corps and Physicians. The Caduceus staff is winged with two serpants entwined on it and was carried by Hermes, messenger to the Gods.