Leaven of Dough, Ferment of Gold: The Breadmaking Analogy in Medieval Metallic Transmutation.

This paper traces the analogy between the making of bread with ferment (leaven or yeast) and theories of metallic transmutation throughout the Middle Ages. For this purpose it surveys several medieval alchemical writings, including Hortulanus's influential . In this work, the ferment, an essential ingredient of the philosophers' stone, is portrayed less as an active agent and more as the passive, nutritive earth () which combines with the soul () in order to yield the stone ().

Medicine, Life, and Transformations of Matter.

This Ambix special issue explores premodern alchemical ideas and practices in their entanglements with medicine. It employs diverse methods, from traditional close reading to the new distant-reading framework of computational humanities, to investigate alchemical thought over a timespan of several centuries. In medieval times, everyday practices could offer heuristic models of material transformation - such as the fermentation of bread as a model for metallic transmutation (Schmechel).

Descartes on fermentation in digestion: iatromechanism, analogy and teleology.

Fermentation is a cornerstone phenomenon in Cartesian physiology, accounting for processes such as digestion or blood formation. I argue that the previously unrecognized conceptual tension between the terms 'fermentation' and 'concoction' reflects Descartes's efforts towards a novel, more thoroughly mechanistic theory of physiology, set up against both Galenism and chymistry. Similarities with chymistry as regards fermentation turn out either epistemologically superficial, or based on shared earlier sources.