In 1875, he received his medical doctorate at Berlin, later working as an assistant physician to Max Schede (1833-1902) at the municipal hospital in Friedrichshain.
In 1883 he became chief physician of the surgical department at the "Marienkrankenhaus" in Hamburg, and in 1895 was appointed surgeon-in-chief of the Allgemeinen Krankenhaus Hamburg-Eppendorf.
Kümmell's work involved the treatment of fractures, bone implants and diseases of the spinal column.
He also conducted extensive research of bladder and kidney disturbances, diseases of the chest, et al.
Among his numerous publications on surgery was Chirurgische Operationslehre, a three-volume work that he co-authored with August Bier (1861-1949) and Heinrich Friedrich Wilhelm Braun (1862-1934).