Bloodletting is one of the oldest forms of treatment in our culture complex. It was already in use as a ritual in biblical-talmudic medicine. In Germany it is still in use today in complementary medicine as "Hildegard's bloodletting". The theoretical principle is based on the four humour philosophy of antiquity which was introduced to medicine as humoral pathology by Galen (129-199 AD). The four humours are blood, phlegm, yellow and black bile. In healthy people these were in equilibrium with each other. Imbalance caused diseases. Bloodletting was performed prophylactically to keep people healthy and to treat almost all serious conditions and injuries. In the Middle Ages many conditions had to be satisfied during the performance. The positions of the stars and the zodiac were vital. A rising moon the in respective sign of the zodiac was considered dangerous. However, age, sex, climate, season of the year, wind direction and the stage of the disease all played a role. Each organ had its own special vein. Even the person performing the bleeding also had to satisfy certain conditions. Surgeons were expected to see well, not to have podgy hands or tremor, and not to be drunk. He had to have sharp instruments and be skilled in their use. Walther Ryff (1500-1562) was a strong advocate of the method at the beginning of modern times in Germany. Bloodletting also included inspection of the blood. To this end, blood was collected in bloodletting vessels, many of which were attractively ornamented. The surgeon also had to assess the taste of the blood. Bloodletting was associated with a wide range of complications before the advent of antiseptic techniques, deaths were not uncommon. It was not until modern times that warning voices started to advise against the procedure; the most vociferous being Christian Friedrich Samuel Hahnemann (1755-1843), the founder of homoeopathy.