The great Paracelsian scholar Walter Pagel and the pioneer medical historian Kurt Polycarp Sprengel identified Petrus Severinus' Idea Medicin (1571) as an influential vehicle for the elaboration and diffusion of Paracelsian ideas in the late sixteenth and early seventeenth centuries, a process that has recently come under renewed scrutiny. Severinus' conception that diseases grow from living, seed-like entities proved to be an especially important...