"I observed certain animalcules, within whole bodies I saw so quick a motion as to exceed belief; they were about the size of a large grain of sand, and their bodies being transparent, that the internal motion could plainly be seen. Among other things, I saw in the body of one of these animalcules a bright and round corpuscle, placed near the head, and in which a very wonderful swift motion was to be seen, consisting of an alternate extension and contraction. This particle I concluded to be the heart."

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The stock market crashed in October 1929. But that was not the cause of what caused the Great Depression. It was, in my opinion, a very minor element of it. What happened was that from 1929 to 1933 you had a major contraction which, in my opinion, was caused primarily by the failure of the Federal Reserve System, to follow the course of action for which it was set up. It was set up to prevent exactly what happened from 1929 to 1933. But instead of preventing it, they facilitated it.

— Milton Friedman