A teacher was giving a lesson on the circulation of the blood.
Trying to make the matter clearer, she said,
"Now, class, if I stood on my head, the blood, as you know,
would run into it, and I would turn red in the face."
"Yes," the class said.
"Then why is it that while I am standing upright in the
ordinary position the blood doesn't run into my feet?"
A little fellow shouted, "Cause yer feet ain't empty."
