 Afterwards he was an assistant in Dresden under pathologist Christian Georg Schmorl (1861-1932), in Paris at the Pasteur Institute under Ilya Ilyich Mechnikov (1845-1916), in Hamburg under American-born hygienist William Philipps Dunbar (1863-1922), and at the Berlin institute of hygiene under Max Rubner (1854-1932).In 1905 Weichardt was habilitated for hygiene and experimental therapy at the University of Erlangen, where he later became a professor and director of the "Bayerische Bakteriologische Untersuchungsanstalt".He made contributions in his research of anaphylaxis, metabolism and fatigue.