So I'm reading Ovid's Metamorphoses [translated by Allen Mandelbaum] for the nth time, enjoying it immensely. Ovid is such an overwrought, yet mellifluous, writer with a constant sense of fun.
One of my favorite Ancient Greek/Roman myths concerns Tiresias, a seer. He was walking along when he saw two snakes mating. He struck the female snake with his staff and changed sex to be a woman. After being a woman for 7 years, Tiresias came upon mating snakes again. He struck the male snake with his staff and changed sex to be a man.
After that, the gods had a fight about who enjoyed sex more, men or women. Zeus said it was women. Hera said it was men. They asked Tiresias to decide, since he had been both. He said women enjoyed sex more. Hera got pissed and blinded him in vengeance.
Tiresias passed the Amazing Transsexual Stick on to Hermes, messenger god, whose symbol is a winged staff called a caduceus with two snakes wrapped around it. This is not the same snake on a cane as Aesclepius' rod, a medical symbol which probably comes from the way that ancient doctors tried to get, say, tapeworms out of people: by wrapping one end of the worm around a stick and pulling. More than you ever wanted to know here.
Aesclepius' rod most properly symbols the medical practice that performs transsexual operations. Hermes' rod most properly symbolizes transgendered persons who have had sex-change operations!
See Snakes on a Cane [a caduceus] below...