Robert Chesebrough believed in his product. He's the fellow who invented Vaseline, a petroleum jelly refined from rod wax, the ooze that forms on shafts of oil rigs. He so believed in the healing properties of his product that he became his own guinea pig. He burned himself with acid and flame; he cut and scratched himself so often and so deeply that he bore the scars of his tests the rest of his life. But he proved his product worked. People had only to look at his wounds, now healed, to see the value of his work--and the extent of his belief.