 He served as physician to the city of Worms in the service of Katherine, wife of Henry IV, Duke of Brunswick-Lüneburg.While examining and supervising the city's midwives, he found their practice of midwifery to be careless and substandard, leading to high rates of infant mortality.As a result, he wrote his book in German, to make it accessible, and published it in the then-German city of Strasbourg.