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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.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.