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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
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 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).
It is difficult to obtain enough calcium without consuming milk or other dairy foods.
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.