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During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
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.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The B-complex vitamins and vitamin C are not stored in the body and must be replaced each day.