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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).
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
Patients who cannot swallow may receive nutrition via a parenteral route—usually, a catheter is inserted through the chest into a large vein going into the heart.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.