In 1931 Ernst Klein became the first full professor for naturopathy at the Friedrich Schiller University in Jena. In 1933 he had to vacate his position due to his Jewish origins and later concentration camp imprisonment.
Ernst Klein's successor was the National Socialist Karl Kötschau (1892 - 1945). Under his leadership, the former Polyclinic for Naturopathy was renamed "Clinic and Polyclinic for Biological Medicine".