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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.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
There are immediate benefits of chiropractic adjustments that are visible via magnetic resonance imaging (MRI). It shows that spinal manipulation therapy is effective in decreasing pain and increasing the gaps between the vertebrae, reducing pressure that leads to pain.
The familiar sounds of your heart are made by the heart's valves as they open and close.
The average adult has about 21 square feet of skin.