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The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
Cytomegalovirus affects nearly the same amount of newborns every year as Down syndrome.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
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.