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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Always store hazardous household chemicals in their original containers out of reach of children. These include bleach, paint, strippers and products containing turpentine, garden chemicals, oven cleaners, fondue fuels, nail polish, and nail polish remover.
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.
Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.