A pharmacist walked into his shop to find a man leaning against the wall

"What's wrong with him?", he asked his assistant.

"He came in for cough syrup, but I couldn't find any so I gave him a box of laxatives."

"You idiot" said the chemist, "You can't treat a cough with laxatives."

"Of course you can" the assistant replied, "Look at him.........he daren't cough now!!"