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The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The senior population grows every year. Seniors older than 65 years of age now comprise more than 13% of the total population. However, women outlive men. In the 85-and-over age group, there are only 45 men to every 100 women.
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.