Nuremberg-born Johannes "Hans" Guggenheimer began his medical studies in Berlin, continued them in Munich, and was licensed and awarded his doctorate in 1910.1 He submitted his dissertation, "Studien über das Verhalten hämolytischer Komplemente im salzfreien Medium" (Studies on the Behavior of Hemolytic Complements in Salt-Free Medium), to the Medical Faculty of the University of Heidelberg.2 He became an assistant at the III. Medical University Clinic in Berlin under Alfred Goldscheider (1858-1935) the same year.3 He habilitated at the clinic in internal medicine In 1918 and was appointed non-civil servant extraordinary professor in 1922. 4 He was registered at the following addresses during his Berlin years, Roonstraße 1 and later Landgrafenstraße 19.5
In addition to cardiological and nephrological diseases, his main research interests included studies of the effects of enzymes.6
Guggenheimer was dismissed from university service because of his Jewish ancestry in 1933.7 He lost his teaching license in 1935 because of the "Reichsbürgergesetz" (Reich Citizenship Law).8
Increasing repression resulted in the withdrawal of his license to teach at the end of September 1938, and Guggenheimer decided to flee. He emigrated to Stockholm in March 1939,9 and left Sweden for New York just a couple of weeks later on the Norwegian ship "SS Bergensfjord." He arrived in New York on April 15, 1940.10 He had thus followed his son Helmut Ernst Guggenheimer, born in 1920, who had already been living in the USA under the name Harold Hastings since 1938. His father moved in with him in Cleveland, Ohio.11 Another son of Hans Guggenheimer, born in 1922, had also emigrated to the U.S. and called himself Peter Hastings.12
Ohio was one of the few states in the U.S. where American citizenship was not a prerequisite for licensure.13 However, applicants were required to take additional university courses in state history and professional language before being granted licensure.14 Guggenheimer enrolled at Ohio State University for this purpose. He was licensed in January 1941 and henceforth practiced medicine again.15 He received American citizenship on June 29, 1945, and took the name Harry Guggenheimer.16