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The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.
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.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
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