"In my case," said the student to the sex researcher, "when I get it part way in, my vision blurs. And when it's all the way in, I can't see a thing." "Now, that's an most interesting optical reaction, that may well have anatomical as well as physiological basis." the researcher replied. "If you don't mind young man, I should like to have a look at it." So, the student volunteer shrugged and stuck out his tongue.