There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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Cyanide works by making the human body unable to use oxygen.
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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.
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Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
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Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
American Hairless Terrier
Glaucoma. (a) A buildup of pressure within the eye cavities, often caused by a blockage of vessels t
The American clipper ship, Red Jacket, off Cape Horn, sails from Australia to Liverpool, England, in
A sidewheeler on the Mississippi. In 1856 Samuel Clemens became an apprentice to a steamboat pilot a