Subsequently, he became an assistant to Joseph von Mering at the University of Halle, and afterwards worked under neurologist Ludwig Lichtheim in Königsberg. Later he was an assistant to dermatologist Paul Gerson Unna in Hamburg and to internist Ernst Viktor von Leyden in Berlin.
He then moved on to become a junior colleague of Joseph von Mering at the University of Halle, followed by stints working under neurologist Ludwig Lichtheim in Königsberg. He also worked as an assistant to dermatologist Paul Gerson Unna in Hamburg and internist Ernst Viktor von Leyden in Berlin.