Joseph Hyrtl once examined a particularly nervous candidate for a medical degree: "What can you tell me about the function of the spleen?" he began.

"Herr Professor," the candidate stammered, wiping his brow. "I did know exactly what it was -- I knew it just a moment ago, but I've now forgotten."

"Miserable creature!" Hyrtl cried. "You're the only man in the world who knows anything about the function of the spleen -- and now you've forgotten it!"