A doctor went on holiday leaving his son-----a newly qualified doctor---- in charge of his practice. "How did it go?" he asked his son when he returned.

　　"You know Mr. Jones and Mrs. Williams?" said his son enthusiastically. "Well, you’ve been treating them for years, but I cured them both in a week!"

　　"Really?" said his father. "And just who do you think was paying for your education all these years?"