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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.
The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).
It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Today, nearly 8 out of 10 pregnant women living with HIV (about 1.1 million), receive antiretrovirals.