He studied classical philology at the Universities of Bonn and Tübingen, receiving his doctorate in 1863 with a dissertation on the Roman scholar Marcus Terentius Varro. In 1870 he began work as a librarian at the Universitätsbibliothek in Freiburg, followed by professorships at the Universities of Innsbruck (1871) and Kiel (1873). In 1874 he was named Oberbibliothekar (head librarian) at the University of Königsberg, shortly afterwards, given the same title at the Niedersächsische Staats- und Universitätsbibliothek in Göttingen (1875).
From 1886 to 1914 he was general director of the Königliche Bibliothek (Royal Library) in Berlin, where he was successor to Karl Richard Lepsius. During his tenure at Berlin, he was credited with conducting a comprehensive reorganization of the library. In 1895 he established a Gesamtkatalog (centralized catalog), initially for Prussia, later being extended to include research libraries in all German-speaking countries.