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Blood is approximately twice as thick as water because of the cells and other components found in it.
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.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
The term bacteria was devised in the 19th century by German biologist Ferdinand Cohn. He based it on the Greek word "bakterion" meaning a small rod or staff. Cohn is considered to be the father of modern bacteriology.