 Complete the following phrase:  He was born in Skien, and took his examen artium in 1925. The cand.med. degree at the University of Oslo followed in 1931, and from 1931 to 1933 he worked at various Norwegian hospitals. After starting a specialist education in microbiology in 1933, at the Bacteriological Laboratory of the Norwegian Armed Forces, he took the dr.med. degree in 1936 on the thesis Studies on the Bacterial Flora of the Respiratory Tract in Acute and Chronic Bronchitis, Bronchial Asthma and Lung Gangrene. He spent the period 1937 to 1938 as research assistant on an expedition to Tristan da Cunha in the South Atlantic, and 1939 to 1941 at Columbia University in the United States. He did not return to German-occupied Norway after the 