In a biology class, the professor was discussing the high glucose levels found in semen. A young female freshman raised her hand and asked, "If I understand, you're saying there is a lot of glucose, as in sugar, in male semen?"

"That's correct," responded the professor, going on to give more statistical info.

Raising her hand again, the girl asks, "Then why doesn't it taste sweet?" After a stunned silence, the whole class burst out laughing. The poor girl's face turned bright red, and as she realized exactly what she had inadvertently said (or rather, implied), she picked up her books without a word and walked out of class... and never returned.

However, as she was going out the door, the Professor's classic deadpan reply was, "It doesn't taste sweet, because the taste-buds for sweetness are on the tip of your tongue."