“Yes.” Vitellius studied the vials approvingly. “Blood taken from the right side of a gorgon’s body can cure any disease, even bring the dead back to life. The goddess Minerva once gave a vial of it to my divine ancestor, Aesculapius. But blood taken from the left side of a gorgon—instantly fatal. So, which is which?”
Frank looked down at the vials. “I don’t know. They’re identical.”

The Son of Neptune, Chapter IX