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Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
The familiar sounds of your heart are made by the heart's valves as they open and close.
In 1864, the first barbiturate (barbituric acid) was synthesized.
The Centers for Disease Control and Prevention (CDC) was originally known as the Communicable Disease Center, which was formed to fight malaria. It was originally headquartered in Atlanta, Georgia, since the Southern states faced the worst threat from malaria.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.