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There are 20 feet of blood vessels in each square inch of human skin.
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.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
Most fungi that pathogenically affect humans live in soil. If a person is not healthy, has an open wound, or is immunocompromised, a fungal infection can be very aggressive.
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.