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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
To maintain good kidney function, you should drink at least 3 quarts of water daily. Water dilutes urine and helps prevent concentrations of salts and minerals that can lead to kidney stone formation. Chronic dehydration is a major contributor to the development of kidney stones.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.
As of mid-2016, 18.2 million people were receiving advanced retroviral therapy (ART) worldwide. This represents between 43–50% of the 34–39.8 million people living with HIV.
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.
![The Dall sheep, Ovis dalli, a mountain sheep of far northern North America, was the subject of one o](https://biology-forums.com/gallery/47/medium_33_22_09_11_9_35_55_18001324.jpeg)
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