He was born with a hunger he could not explain. It frightened him, this not knowing, because if he did not know what the hunger was, how could he ever satisfy it?
As he grew to manhood, the hunger grew also. Sometimes it seemed as if it were devouring him; no matter what he ate, he remained gaunt. Only during sex could he forget the hunger.
One day while kissing his girlfriend, he accidentally drew blood. And suddenly it all made sense.
With a happy sigh, he sunk his teeth in the neck of the struggling girl.
And found fulfillment.