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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.
Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
By definition, when a medication is administered intravenously, its bioavailability is 100%.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.
![L. Frank Baum, author of The Wonderful Wizard of Oz (1900) and a fan of William Jennings Bryan, perh](https://biology-forums.com/gallery/47/medium_376716_26_08_15_11_16_37_22450198.jpeg)
![(a) The phagocytic process, beginning in the upper left with bacterial attachment and phagocytic ...](https://biology-forums.com/gallery/31/medium_398119_11_07_17_2_55_16_31464219.jpeg)