How do cathartic drugs act? A case study on Gregor Horst (1578-1636) and his attempt to defend Galenist theory.

This case study deals with the argument of the Galenist author Gregor Horst (1578-1636), Medical Professor at Giessen University, Germany, and later town phyusician in Ulm, in the discussion on how purgatives act. Horst tried to reconcile a number of different opinions within a Galenist framework. His vast erudition enabled him to compare several classical as well as contemporary opinions. He takes into account Galen (129-c.200/216), Erasistratos (c. 330-255 BC), Asclepiades (fl. 1st century BC), the Hippocratic Corpus and the Problemata Aristotelis from antiquity, Mesue and Mundinus (c. 1270-1326) from the Middle Ages, and Jean Fernel (c. 1497-1558), Girolamo Cardano (1501-c. 1576), Johannes Costaeus (d. 1603), Laurent Joubert (1529-1583), Francisco Valles (1524-1592), Tobias Dorncreilius (1571-1605) and Gavriele Falloppio (1523-1562) from contemporary authors. Horst also integrated some Paracelsian ideas from Joseph Duchesne alias Quercetanus (1549-1609). In his attempt to preserve fundamentals of Galenic thought, Horst created a complicated theory nearly breaking under its own weight. He shows a rising divergence within traditional views as well as the fragmentation of Renaissance Galenism which took place already before the discovery of the blood circulation.