The English physician John of Arderne (1307–ca. 1380) is remembered as one of the founding figures of modern surgery. He was one of the earliest scholarly “master surgeons”, who differentiated themselves — through rigorous training and by thoroughly documenting their techniques — from the barber-surgeon generalists that were still blood-letting and pulling teeth across Europe. Arderne authored De Arte Phisicali et de Cirurgia (On the Art of Medicine and Surgery), a treatise full of actionable instructions for a wide range of maladies. Pharmacological recipes appeared for kidney stones, sciatica, poisoning (by toad bite and scorpion sting), cataracts, and “frenzy”. Ingredients ranged from the culinary (egg white, rye bread) to the unsavory (earthworms, “the urine of a virgin”). Most famously, Arderne’s Fistula in Ano includes detailed descriptions for the surgical treatment of anal fistulas (apparently, a more common issue in horseback riding’s heyday). Dozens of manuscripts transcribing Arderne’s work survive today: testament to how useful his guide was to the working surgeon. So useful was Fistula in Ano, finds historian Peter Murray Jones, that the text remained a well-trafficked reference work until the late 1600s.