A teacher was giving a lesson about the circulation of blood. He said: "Now boys, as you know, if I stood on my head, the blood would run into it and I would turn red in the face."
"Yes, sir," they chorused.
"So why is it," asked the teacher, "that when I am standing upright, the blood doesn't run into my feet and make them turn red, like my head?"
"A young voice from the back called out: "Because your feet aren't empty!"
"Yes, sir," they chorused.
"So why is it," asked the teacher, "that when I am standing upright, the blood doesn't run into my feet and make them turn red, like my head?"
"A young voice from the back called out: "Because your feet aren't empty!"