To answer your last question: while the theory of the Four Humors have fallen out of favor with modern medicine, the practice of draining blood for therapeutic reasons has not gone away. Certain conditions of the blood lead to iron overload (aka over the amount needed to maintain normal levels of red blood cells), a condition that will lead to organ damage over time. The body is not terribly good at getting rid of iron. For acquired or hereditary hemachromatosis, therapeutic phlebotomy can be used to bring iron levels back to normal.

Source: http://www.cdc.gov/ncbddd/hemochromatosis/training/treatment/phlebotomy_treatment.html