An old G.P. and his nurse

An old G.P. and his nurse were on the train, going to a Medical Conference.
Opposite them was a man furiously scratching his elbow?

I wonder what's the matter with him? asked the nurse.

He's a patient of mine and, in confidence, I can tell you that he suffers
badly from hemorrhoids, replied the G.P.

Well, why he's scratching his elbow? asked the puzzled nurse.

Oh, he's a politician, and he doesn't know his ass from his elbow.