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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.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Glaucoma is a leading cause of blindness. As of yet, there is no cure. Everyone is at risk, and there may be no warning signs. It is six to eight times more common in African Americans than in whites. The best and most effective way to detect glaucoma is to receive a dilated eye examination.
In 1864, the first barbiturate (barbituric acid) was synthesized.