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Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
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 oncogene was discovered in 1970 and was termed SRC (pronounced "SARK").
Alzheimer's disease affects only about 10% of people older than 65 years of age. Most forms of decreased mental function and dementia are caused by disuse (letting the mind get lazy).
In most climates, 8 to 10 glasses of water per day is recommended for adults. The best indicator for adequate fluid intake is frequent, clear urination.
![The urinary system: kidneys, ureters, bladder, and urethra with expanded view of a nephron and the u](https://biology-forums.com/gallery/47/medium_14755_05_10_12_4_15_35_92751702.jpeg)
![Urinary catheterization. The procedure involves the insertion of a flexible tube, or catheter, throu](https://biology-forums.com/gallery/47/medium_14755_26_10_12_5_21_07_96742390.jpeg)