Heinrich Petraeus (Henricus Petraeus) (1589–1620) was a German physician and writer. He was Professor of Medicine at the University of Marburg. He was son-in-law of the chemist Johannes Hartmann (1568–1631). He is known for his Nosologia Harmonica Dogmatica et Hermetica.[1] This was an attempt to find concord between rival medical theories of the time: those of the progressive chemical physicians (exemplified by Vesalius) and those of the tradition-based Galenists.[2]