Doctor bleeding patient. Coloured historical artwork of a doctor bleeding a patient. Blood is collecting in a bowl from an incision in the man's arm. The incision was usually made, under the supervision of a physician, by a barber-surgeon. Despite the medical advances of the Renaissance, many physicians perpetuated medieval beliefs and practices. They thought that illnesses were the result of an imbalance in the four humours (bodily fluids). For example high blood pressure was due to too much blood. Consequently the treatment involved draining excess blood through a cut or by using leeches. The artwork was made by the English caricaturist James Gillray (1757-1815) in 1804.