A Professor was giving a lecture on "Involuntary Muscular Contractions" to his first year medical students. Realizing that this was not the most riveting subject, the Professor decided to give an example his students could relate to.

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

She replied, "He's probably golfing with his friends."