This article traces a seven-hundred-year history of one puzzling treatment for plague buboes that used the rumps of chickens to draw out the bubo's poisons. It traces the origin of the recipe to Avicenna's Canon and explores how medieval and early modern physicians altered the treatment and explained its workings up to the early eighteenth century. Much of the analysis focuses on the variants of the recipe that German physicians created as they adapted or elaborated on older recipes. This article argues that most variations of the treatment likely resulted from physicians trying ideas on paper, rather than in practice, as they attempted to unlock the mysteries of the plague's underlying poisons. Starting in the sixteenth century, however, evidence suggests that practice began to play an important role in the adaptation and interpretation of the "live chicken" recipes.