A professor at the University of Sydney was giving a lecture on 'Involuntary Muscular Contractions' to his first year medical students.

Realising this was not the most riveting subject, the professor decided to lighten the mood slightly.

He pointed to a young woman in the front row and said, 'Do you know what your arsehole is doing while you're having an orgasm?'

She replied, 'Probably fishing with his mates.'

It took 45 minutes to restore order in the classroom.........