A biology professor at the University of Australia was giving a lecture on "Involuntary Muscular Contractions" to his first-year medical students. Realising that 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 asked, "Do you know what your arsehole is doing while you're having an orgasm?" "Probably out fishing with his mates!!" she replied.