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It is difficult to obtain enough calcium without consuming milk or other dairy foods.
There are 20 feet of blood vessels in each square inch of human skin.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The term bacteria was devised in the 19th century by German biologist Ferdinand Cohn. He based it on the Greek word "bakterion" meaning a small rod or staff. Cohn is considered to be the father of modern bacteriology.
Historic treatments for rheumatoid arthritis have included gold salts, acupuncture, a diet consisting of apples or rhubarb, nutmeg, nettles, bee venom, bracelets made of copper, prayer, rest, tooth extractions, fasting, honey, vitamins, insulin, snow collected on Christmas, magnets, and electric convulsion therapy.
![The nitrogen cycle. Numbers represent fluxes as 1012 g N per year (data from Schlesinger 1991, after](https://biology-forums.com/gallery/47/medium_33_17_02_12_7_02_17_2038129.jpeg)
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