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Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
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.
Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.