Once upon a time there was a doctor who awakened one morning with a splitting headache. As he groggily approached his shaving mirror in the dim light, he thought he was hallucinating and vowed to consume no more midnight snacks of smoked oysters and sliced onion. “Splitting” had indeed been the appropriate adjective to describe his headache, for to his utter amazement he saw, as his vision cleared, that he had grown a second head. Examining his second head closely, he saw that it was identical in appearance to his original head, and, much like that of his child's pet . . .