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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.
On average, the stomach produces 2 L of hydrochloric acid per day.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
The first oncogene was discovered in 1970 and was termed SRC (pronounced "SARK").
The first war in which wide-scale use of anesthetics occurred was the Civil War, and 80% of all wounds were in the extremities.