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More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Vaccines prevent between 2.5 and 4 million deaths every year.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.
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