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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.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.
Vaccines prevent between 2.5 and 4 million deaths every year.
Cocaine was isolated in 1860 and first used as a local anesthetic in 1884. Its first clinical use was by Sigmund Freud to wean a patient from morphine addiction. The fictional character Sherlock Holmes was supposed to be addicted to cocaine by injection.