English: Treatment with leeches. Historical artwork of a woman using leeches to treat disease. She has taken some of the blood-sucking leeches out of a jar at left and placed them on her arm. Leeches were prescribed to treat diseases thought to be caused by the presence of too much blood in the body. While this medical theory has been disproved, leeches are sometimes used today to drain areas of partially clotted blood (haematomas) from a wound. This woodcut is from Historia Medica by W. van den Bossche, which was published in 1638.