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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.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Adult head lice are gray, about ? inch long, and often have a tiny dot on their backs. A female can lay between 50 and 150 eggs within the several weeks that she is alive. They feed on human blood.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
About one in five American adults and teenagers have had a genital herpes infection—and most of them don't know it. People with genital herpes have at least twice the risk of becoming infected with HIV if exposed to it than those people who do not have genital herpes.