These are one of the funniest kind of jokes because the Medical profession is otherwise a serious profession.
The patient was seen running down the hall of the hospital just before his operation.

"What's the matter?" someone asked him.

He said, "I heard the nurse say, 'It's a very simple operation, don't worry, I'm sure it will be all right."

"She was just trying to comfort you, what's so frightening about that?"

"She was talking to the doctor.