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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.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.
An identified risk factor for osteoporosis is the intake of excessive amounts of vitamin A. Dietary intake of approximately double the recommended daily amount of vitamin A, by women, has been shown to reduce bone mineral density and increase the chances for hip fractures compared with women who consumed the recommended daily amount (or less) of vitamin A.
In 1844, Charles Goodyear obtained the first patent for a rubber condom.