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Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.
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.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
A seasonal flu vaccine is the best way to reduce the chances you will get seasonal influenza and spread it to others.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.