Bloodletting

Bloodletting (or blood-letting) is the deliberate withdrawal of blood from a patient to prevent or cure illness and disease. Bloodletting, whether by a physician or by leeches, was based on an ancient system of medicine in which blood and other bodily fluids were regarded as "humors" that had to remain in proper balance to maintain health. It was the most common medical practice performed by surgeons from antiquity until the late 19th century, a span of over 2,000 years. In Europe, the practice continued to be relatively common until the end of the 19th century. The practice has been abandoned by modern-style medicine for all except a few very specific medical conditions. In the beginning of the 19th century, studies had begun to show the harmful effects of bloodletting.

The modern term phlebotomy refers to the drawing of blood for laboratory analysis or blood transfusion. Therapeutic phlebotomy refers to the drawing of a unit of blood in specific cases like hemochromatosis, polycythemia vera, porphyria cutanea tarda, etc., to reduce the number of red blood cells. The traditional medical practice of bloodletting is considered a pseudoscience, though the method is still commonly used in forms of alternative medicine.

Passages from the Ebers Papyrus may indicate that bloodletting by scarification was an accepted practice in Ancient Egypt. Egyptian burials have been reported to contain bloodletting instruments. According to some accounts, the Egyptians based the idea on their observations of the hippopotamus, confusing its red secretions with blood and believing that it scratched itself to relieve distress.

In Greece, bloodletting was in use in the 5th century BC during the lifetime of Hippocrates, who mentions this practice but generally relied on dietary techniques. Erasistratus, however, theorized that many diseases were caused by plethoras, or overabundances, in the blood and advised that these plethoras be treated, initially, by exercise, sweating, reduced food intake, and vomiting. But his student Herophilus supported bloodletting. A contemporary Greek physician, Archagathus, one of the first to practice in Rome, also believed in the value of bloodletting.^{[citation needed]}

"Bleeding" a patient to health was modeled on the process of menstruation. Hippocrates believed that menstruation functioned to "purge women of bad humours". During the Roman Empire, the Greek physician Galen, who subscribed to the teachings of Hippocrates, advocated physician-initiated bloodletting.

The popularity of bloodletting in the classical Mediterranean world was reinforced by the ideas of Galen, after he discovered that not only veins but also arteries were filled with blood, not air as was commonly believed at the time. There were two key concepts in his system of bloodletting. The first was that blood was created and then used up; it did not circulate, and so it could "stagnate" in the extremities. The second was that humoral balance was the basis of illness or health, the four humours being blood, phlegm, black bile, and yellow bile, relating to the four Greek classical elements of air, water, earth, and fire respectively. Galen believed that blood was the dominant humour and the one in most need of control. In order to balance the humours, a physician would either remove "excess" blood (plethora) from the patient or give them an emetic to induce vomiting, or a diuretic to induce urination.

Galen created a complex system of how much blood should be removed based on the patient's age, constitution, the season, the weather and the place. "Do-it-yourself" bleeding instructions following these systems were developed. Symptoms of plethora were believed to include fever, apoplexy, and headache. The blood to be let was of a specific nature determined by the disease: either arterial or venous, and distant or close to the area of the body affected. He linked different blood vessels with different organs, according to their supposed drainage. For example, the vein in the right hand would be let for liver problems and the vein in the left hand for problems with the spleen. The more severe the disease, the more blood would be let. Fevers required copious amounts of bloodletting.

The Talmud recommended a specific day of the week and days of the month for bloodletting in the Shabbat tractate, and similar rules, though less codified, can be found among Christian writings advising which saints' days were favourable for bloodletting.^{[citation needed]} During medieval times bleeding charts were common, showing specific bleeding sites on the body in alignment with the planets and zodiacs. Islamic medical authors also advised bloodletting, particularly for fevers. It was practised according to seasons and certain phases of the Moon in the lunar calendar. The practice was probably passed by the Greeks with the translation of ancient texts to Arabic and is different than bloodletting by cupping mentioned in the traditions of Muhammad. When Muslim theories became known in the Latin-speaking countries of Europe, bloodletting became more widespread. Together with cautery, it was central to Arabic surgery; the key texts Kitab al-Qanun and especially Al-Tasrif li-man 'ajaza 'an al-ta'lif both recommended it. It was also known in Ayurvedic medicine, described in the Susruta Samhita.