Erich Lessing / Art Resource, NY

The fifth-century B.C. doctor Hippocrates, one of the most famous ancient physicians, sits in the presence of the sun-god Apollo (far left) and the centaur Chiron, in this first-century A.D. fresco from Pompeii. In Greek mythology, Apollo is Asklepios’s father, and Chiron tutors him in the art of medicine. Apollo has traditionally been associated with medicine; when ancient doctors entered the profession, they swore allegiance to “Apollo Physician and Asklepios.”