Johannes Fibiger

Fibiger, a Danish physician and professor of anatomical pathology at the University of Copenhagen, found roundworms in wild rats in 1907 and suspected they caused the stomach cancers he observed. By 1913 he reported he could experimentally induce cancer in healthy rats using the parasite - a claim hailed at the time as "the greatest contribution to experimental medicine." He was passed over for the 1926 Nobel alongside another researcher, then retrospectively awarded it alone the following year. After his death in 1928, independent work dismantled the finding: the roundworm Gongylonema neoplasticum couldn't cause cancer, and what Fibiger had seen were non-cancerous lesions triggered by vitamin deficiency. His diphtheria research, though, laid groundwork for the controlled clinical trial.