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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.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
Cyanide works by making the human body unable to use oxygen.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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).