This illustration shows the various stages of Arderne's operation which was designed to cut the tissue between the fistula wall and rectum. The operation, described by the Spanish physician, Albucasis (936-1013), was considered extremely dangerous and half of Arderne's patients were believed to have died. However, by Medieval standards, this would have been considered very acceptable. Arderne became famous and never charged less than 100 shillings for the operation. If patients were rich, he raised his fee to £40.London: British Museum, MS Sloane 56, folio 44. John Arderne. Liber medicinarum.Source: Loren MacKinney. Medical illustrations in Medieval manuscripts. Wellcome Historical Medical Library, London 1965.