Cohnheim, Julius Friedrich (1839–1884)

German pathologist who devised new ways of looking at specimens of human tissue under the microscope and worked out many of the early cellular events that occur in inflammation.

Cohnheim devised a variety of innovative methods for viewing slices of human tissue under the microscope to show that the essence of the inflammatory response is the migration of white blood cells to a wound. The inflammatory response results in an increased flow of blood to the site of injury and an increased permeability of the endothelium (the thin tissue that comprises the walls of capillaries). Both of these effects assist the migration of phagocytic (germ-engulfing) white blood cells from the blood to the interstitial fluid. Here the white blood cells can begin engulfing debris and any infecting micro-organisms. Cohnheim also demonstrated that when inflammation subsides, the remaining pus consists largely of dead white blood cells.

Cohnheim was born in Demmin, Poland (now Germany). He studied in Berlin, where he graduated in medicine and studied for a year with the eminent cellular pathologist Rudolf Virchow.

Cohnheim held chairs in pathology at Breslau and Leipzig. His textbook of pathology Lectures on General Pathology, 1877–1880, runs to two volumes and was one of the first textbooks to combine pathological anatomy and morbid histology.