How did Julius Friedrich Cohnheim challenge Rudolf Virchow’s view of inflammation?

Rudolf Virchow, the founder of cellular pathology, held a significant but incomplete understanding of inflammation. While he advanced the field by establishing that disease processes occur at the cellular level, he erroneously rejected the possibility that leukocytes could migrate from the blood into tissues.1

His former pupil, Julius Friedrich Cohnheim, challenged this view through his experimental research. By 1867, Cohnheim confirmed that inflammation is fundamentally characterized by the passage of leukocytes through capillary walls and into the surrounding tissues. He further demonstrated that pus is primarily composed of the debris resulting from the disintegration of these migrated white blood cells. Cohnheim’s findings, which he later summarized in his 1873 work Neue Untersuchungen über die Entzündung ("Recent Researches on Inflammation"), provided a critical correction to Virchow’s earlier theories regarding the inflammatory process.2