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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.
There are more bacteria in your mouth than there are people in the world.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
Blood is approximately twice as thick as water because of the cells and other components found in it.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.