1856-1939 1873-1956 1878-1949 1888-1943 193 aichhorn artists august correspondence correspondencebissier correspondenceschlemmer etlapédagogiefreud freud germany hans histoire history julius methodology méthodologie oskar oskarrobert pfister philosophypsychoanalysiseducation psychanalyse psychoanalysis sigmund studyandteaching zulliger étudeetenseignement