A teacher I knew told how he always had trouble with a particular class of 14 year olds when he came to explain the joys of human reproduction. Inevitably, the boys, in particular, would snigger and whisper during his lesson and no admonishment or threat on his part seemed to affect the mature reflection he desired. Then, one day, he found the solution without really trying. Turning suddenly from the blackboard, he bore down on a hapless boy caught giggling to the student next to him. At the top of his voice the teacher commanded, “You, son! What’s a penis?” Apparently the remainder of the lesson assumed an unusual gravitas both profound and undisturbed.