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It is difficult to obtain enough calcium without consuming milk or other dairy foods.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.
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).