came from Richard Douglas Passey, with his colleagues A. Léese, and J.C. Knox. They reported a new finding in 1935 that S. carcinoma do not cause cancer in rats. They concluded that Fibiger probably had mistaken metaplasia (a non-cancerous tumour) with malignant neoplasia (true cancer). In 1937, W. Cramer experimentally showed that Fibiger's tumour were not cancerous. The final disproof was shown by Claude R. Hitchcock and E. T. Bell. In 1952, they repeated Fibiger's experiments using advanced microscopy and histology, and conclusively demonstrated that the tumours due to G. Neoplasticum in rats were non-cancerous tumours. And the tumours were primarily due to vitamin A deficiency. It is also claimed that exclusion of Yamagiwa was another mistake. Yamagiwa's work has become the primary basis for induction of tumours in cancer research. Because of this, some consider Fibiger's Nobel Prize to be undeserved particularly because Yamagiwa did not receive the prize. Encyclopædia Britannica guide to Nobel Prizes in cancer research mentions Yamagiwa's work as a milestone without mentioning Fibiger. Although G. Neoplasticum is non-carcinogenic, other helminth parasites such as Schistosoma haematobium, Opisthorchis viverrini and Clonorchis sinensis are now established to cause cancer in humans. See also Carcinogenic parasite References Further reading Nobel Lectures, Physiology or Medicine 1922–1941, Elsevier Publishing Company, Amsterdam, 1965. External links including the Nobel Lecture on 12 December 1927 Investigations on Spiroptera Carcinoma and the Experimental Induction of Cancer Biography from WhoNamedIt Biography from YourDictionary 1867 births 1928 deaths Nobel laureates in Physiology or Medicine Danish Nobel laureates Danish bacteriologists Danish pathologists University of Copenhagen alumni Academic staff of the University of Copenhagen Rectors of the University of Copenhagen People from Silkeborg Burials at the Garrison Cemetery, Copenhagen