He devoted himself to the study of history of medicine. Socialized Medicine in the Soviet Union (1937), and History of Medicine were among his most important works. He emerged as a major spokesman for "compulsory health insurance". From 1932 to 1947 was director at Johns Hopkins University institute of history of medicine. He received financial aid from the Rockefeller Institute. He attacked the American Medical Association because of his conflicting views on socialized medicine.