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Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
Stroke kills people from all ethnic backgrounds, but the people at highest risk for fatal strokes are: black men, black women, Asian men, white men, and white women.
Vaccines prevent between 2.5 and 4 million deaths every year.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.
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.