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The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.
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.
Patients who cannot swallow may receive nutrition via a parenteral route—usually, a catheter is inserted through the chest into a large vein going into the heart.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.