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Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
In 1844, Charles Goodyear obtained the first patent for a rubber condom.
Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
When Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
On average, the stomach produces 2 L of hydrochloric acid per day.