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The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.

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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.

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Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).

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Signs and symptoms that may signify an eye tumor include general blurred vision, bulging eye(s), double vision, a sensation of a foreign body in the eye(s), iris defects, limited ability to move the eyelid(s), limited ability to move the eye(s), pain or discomfort in or around the eyes or eyelids, red or pink eyes, white or cloud spots on the eye(s), colored spots on the eyelid(s), swelling around the eyes, swollen eyelid(s), and general vision loss.

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Women are two-thirds more likely than men to develop irritable bowel syndrome. This may be attributable to hormonal changes related to their menstrual cycles.

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