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There are 20 feet of blood vessels in each square inch of human skin.
Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.
In 1844, Charles Goodyear obtained the first patent for a rubber condom.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.