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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
There are more bacteria in your mouth than there are people in the world.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
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).