He discovered that in German, longer words used shorter syllables (based on phonemes) and he suggested that other languages may also follow this principle and was able to confirm it for Spanish.
He listened to lectures by Levy, Lommatzsch, Puchstein, Rickert and Steup in Freiburg, Dessau, Dessoir, Diels, Ebeling, Helm, Imelmann, Klebs, Less, etc.
Luschan, Menzer, Pariselle, Paulsen, Rawitz, Rothstein, Schmidt, P. Schultz, Wilhelm Schulze, v. Stradonitz, Stumpe, Thomas, Vahlen, Wentzel, v. Wilamowitz Moellendorf, Winnefeld in Berlin, Ach, Biiit, Justi, Kalbfleisch, Natorp, Scharff, Thiele, Thumb in Marburg, Külpe, Schneegans, Weygandt in Würzburg.
[4] He established a phonetic laboratory in Bonn which was destroyed by aerial bombing during World War II in October 1944.
In 1943 he was accused of having made derogatory remarks on Hitler during a trip to Sweden and for praising Heinrich Heine.