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The horizontal fraction bar was introduced by the Arabs.

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The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."

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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.

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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.

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Adolescents often feel clumsy during puberty because during this time of development, their hands and feet grow faster than their arms and legs do. The body is therefore out of proportion. One out of five adolescents actually experiences growing pains during this period.

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Time Line of Human History From Upper Paleolithic Period to the Present Time Line of Human History From Upper Paleolithic Period to the Present
The distribution of cones and rods over the human retina. The figure illustrates the number of cones ... The distribution of cones and rods over the human retina. The figure illustrates the number of cones ...
A colorized image of human chromosomes A colorized image of human chromosomes
Apoptosis in the formation of a human hand Apoptosis in the formation of a human hand
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Video: Parkinson's Disease

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