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Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
Approximately 500,000 babies are born each year in the United States to teenage mothers.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.