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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.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Thyroid conditions may make getting pregnant impossible.
Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).
According to the FDA, adverse drug events harmed or killed approximately 1,200,000 people in the United States in the year 2015.