 He published two more epistemological papers in Polish: “Problems of the Science of Science” (1946) and “To Look, To See, To Know” (1947). Those texts do not add anything important to the theory which he formulated in the 1930s. He was absorbed by research on a defence mechanism which he discovered in 1942 and named “leucergy”. It was the chief subject of most of his roughly 80 medical papers which he published in those years, mostly in Polish, but also in English and French. In 1952 he became the director of the bacteriology and immunology laboratory of the Institute of Mother and Child in Warsaw. Fleck was honored with many high national distinctions; he had a company car at his disposal, and attended international conferences abroad. In 1954 he became a member of the Polish Academy of Sciences. 