Mr. Perkins, the anatomy instructor

Mr. Perkins, the anatomy instructor at a posh suburban girl�s college, said
during class, "Miss Smyth, would you please name the organ of the human body,
which under the appropriate conditions, expands to six times its normal size,
and define the conditions."
Miss Smyth gasped, and then said coldly, "Mr. Perkins, I don't think that is a
proper question to ask me. I assure you my parents will hear of this." With
that, she sat down red faced.
Unperturbed, Mr. Perkins called on Miss Summers and asked the same question.
Miss Summers, with composure, replied. "The pupil of the eye, in dim light."
"Correct," said Mr., Perkins. "And now, Miss Smyth, I have three things to say
to you.
One, you have not studied your lesson.
Two, you have a dirt mind...and
Three, you will some day be faced with a dreadful disappointment."