Use of leeches for "safe" bloodletting persisted until the late 19th century. It was believed that leeches were capable of sucking "bad humors" from the body, in addition to blood. The species of leech and the location attached was important: a recorded remedy for headache from the 18th century was to "apply six Algerian dragon leeches to the forehead and temples and allow them to draw blood for two hours."
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