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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.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
In most cases, kidneys can recover from almost complete loss of function, such as in acute kidney (renal) failure.
Asthma cases in Americans are about 75% higher today than they were in 1980.
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.