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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
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.
Cytomegalovirus affects nearly the same amount of newborns every year as Down syndrome.
Medication errors are more common among seriously ill patients than with those with minor conditions.
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