On 1 August 1901 he became an assistant physician at the psychiatric clinic and mental hospital in Freiburg, working under the noted psychiatrist Alfred Hoche, one of the most vocal critics of the "natural disease entities" classification of Emil Kraepelin.
As is the custom in German universities, in order to be eligible for a professorship Bumke researched and wrote a second thesis or Habilitation.
Published in 1904, Bumke's extensive literature review of the evidence for eye-pupil abnormalities in neurological and psychiatric conditions was an attempt to identify potential biomarkers that might be of diagnostic and research significance.
Lenin became ill in Moscow, Bumke was invited to be part of a team of visiting neurological specialists to evaluate and treat —if possible— the ailing leader.
During this period Bumke made the acquaintance of Leon Trotsky and Karl Radek and had favorable impressions of these two men.
Bumke's ascension to these positions marked a striking generational change of direction in Munich and in German psychiatry as a whole.
This lecture appeared in print only 6 weeks before Bumke began his tenure in Munich, thus setting the stage for a heightening of tension between the two men.
He was the editor of psychiatric journals and multivolume sets of research reviews that catalogued and summarized the scientific findings of neurology and psychiatry.