Nobel Prize. It should therefore be just if the prize would be divided between Johannes Fibiger, the discoverer of the experimental spiroptera carcinoma, and Katsusaburo Yamagiwa, the discoverer of the experimental tar carcinoma." But Bergstrand opposed to it, concluding that "an experimental confirmation of a previously known fact... [referring to the prevalence of cancer among chimney sweeps and factory workers, an already established medical fact at the time] can, in this case, not be considered... that one cannot, at this point, find much support for the possibility that the work of Fibiger and Yamagiwa will have great importance in the solving of the riddle of cancer. Under such circumstances I do not consider these discoveries worthy of the Nobel Prize." The Nobel Committee could not make the final decision and decided not to give the prize for 1926. In the next year, Fibiger received seven nominations, and Yamagiwa was then excluded. Instead there were two other nominees, Otto Heinrich Warburg and Julius Wagner-Jauregg. In addition to Henschen and Bergstrand, Einar Hammersten was appointed as the third assessor. On Fibiger, Bergstrand was of the same opinion, Hammersten was in favour. Hence the three nominees were recommended for the award. The Nobel Committee decided to give the 1926 prize jointly to Fibiger and Warburg, and the 1927 prize to Wagner-Jauregg. However, the authority at the Karolinska Institute disagreed with the recommendation for Warburg for undisclosed reasons, and Fibiger became the sole winner. (Warburg was eventually awarded the prize in 1931.) Posthumous criticism and disproof Fibiger's discovery was unchallenged during his lifetime. The only serious criticism was by F. D. Bullock and G. L. Rohdenburg. In 1918, they argued that the cancerous tumours produced in Fibiger's experiments were similar to non-cancerous tumours. Such tumours easily developed in epithelial cells. Fibiger defended "That these tumors are true carcinomata cannot, thus, be doubted, and the fact that they may occur in younger animals does not diminish our right to range them among the true malignant neoplasms." It was only after Fibiger's death that the importance of vitamin A in cancer development was fully appreciated. Fibiger had used rats which were fed vitamin A-less diet. It was found that Vitamin A deficiency alone can cause tumours and cancers. The parasites had merely caused the tissue irritation (chronic inflammation) that drove the damaged cells into cancer; any tissue irritation could have induced the tumours. The major challenge