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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.
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).
More than nineteen million Americans carry the factor V gene that causes blood clots, pulmonary embolism, and heart disease.
Vaccines prevent between 2.5 and 4 million deaths every year.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.