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 as much glucose in male semen as there is in sugar?"
"That's correct," responded the professor, going on to a statistical info.
Raising her hand again, the girl asked, "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 reply was classic. Totally straight-faced he answered her question, "It doesn't taste sweet because the taste-buds for sweetness are on the tip of the tongue and not in the back of the throat."