Portrait of the German pathologist and anthropologist Rudolf Ludwig Carl Virchow (1821- 1902). Virchow was a skillful pathologist. He was the first to recognise leukaemia and also described many other conditions such as thrombosis, embolism and inflammations. In the 1850s he took up Schwann and Schleiden's cell theory and applied it to pathology. He believed that diseases originated within cells and saw them as a continuous change in the cells rather than as a result of an invasive agent as proposed by the germ theory of Pasteur. He was also an enthusiast for anthropology and archaeology and worked on the 1879 dig to discover the site of Troy.