Women's Health Magazine has posted a fascinating quiz to test readers' knowledge of the human penis.

For example, what percentage of men worldwide are circumcised? How much semen is usually produced during an ejaculation? And how long does it take the average man to ejaculate after penetration? Most importantly of all, perhaps, what is the average erect penis size? (Of course, Male Edge users may find they are an inch or two above the average ...)

There are some great questions in there (and some surprising answers), and though the quiz is primarily aimed at women, there's definitely enough in there to keep you interested.