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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
In the ancient and medieval periods, dysentery killed about ? of all babies before they reach 12 months of age. The disease was transferred through contaminated drinking water, because there was no way to adequately dispose of sewage, which contaminated the water.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.