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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.
Most fungi that pathogenically affect humans live in soil. If a person is not healthy, has an open wound, or is immunocompromised, a fungal infection can be very aggressive.
Oliver Wendell Holmes is credited with introducing the words "anesthesia" and "anesthetic" into the English language in 1846.
There are approximately 3 million unintended pregnancies in the United States each year.
Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.