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Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The National Institutes of Health have supported research into acupuncture. This has shown that acupuncture significantly reduced pain associated with osteoarthritis of the knee, when used as a complement to conventional therapies.
There are approximately 3 million unintended pregnancies in the United States each year.