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Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.
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.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
There are 20 feet of blood vessels in each square inch of human skin.