《搜神记·卷十二》
当牛哀是人的时候，他并不知道自己将要变成老虎；当他成为老虎的时候，也不知道自己曾经是人。
其兄启户而入，搏而食之。方其为人，不知其将为虎也；方有为虎，不知其常为人也。
When Niu Ai was a human, he didn't know that he would turn into a tiger; when he became a tiger, he didn't know that he had once been human.