Not all snakes found on gravestones in cemeteries are bad or represent Satan and sin. In Greek mythology, for instance, Asclepius was the god associated with healing. The symbol of the god was a snake coiled around a staff.
The symbolism of the snake and staff has been interpreted many ways. Some see the snake as having powers to rejuvenate itself—it sloughs off its skin and becomes young again in an act of renewal. Others see it as a metaphor for medicine. In ancient times venom was often prescribed as a medicine and in that way could help a patient. On the other hand, if the snake bites you, the snake can hurt or even cause death. Just as with the snake, the physician has life and death in his hands.
Thus, the Rod of Asclepius became the symbol for medical professionals around the world, including the United Nation’s World Heath Organization. In the United States most professional health organizations use the Rod of Asclepius as their symbol.