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The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.
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.
It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
There are 20 feet of blood vessels in each square inch of human skin.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.