virus, later known as Shope papilloma virus, and showed in 1935 that the virus was transmissible in healthy rabbits. Shope realized the similarity as a cancer agent with Rous's virus and requested Rous for further investigation. Rous obliged and soon reported on the details Shope papilloma virus. From his initial study, he knew that such tumor can "undergo progressive changes in the direction of malignancy when they grow vigorously." His research during the next three decades helped to confirm that viral papilloma can lead to cancers. The virus nature of the Rous sarcoma was shown by William Ewart Gye of the National Institute for Medical Research at Hampstead in 1925. The carcinogenic property was widely accepted after the discovery of the oncogene in 1960, the exact gene of which was identified in the 1970s as src. Blood transfusion The outbreak of World War I inspired Rous to turn his attention to blood transfusion, as he learned soldiers were dying at the war fronts due to blood loss. In 1915, he collaborated with Joseph R. Turner to work on the methods of blood transfusion. That year, they deviced a method for testing blood compatibility to avoid complications in transfusion. Although an Austrian physician Karl Landsteiner had discovered blood types a decade earlier, the practical usage was not yet developed, as Rous described: "The fate of Landsteiner's effort to call attention to the practical bearing of the group differences in human bloods provides an exquisite instance of knowledge marking time on technique. Transfusion was still not done because (until at least 1915), the risk of clotting was too great." He and Turner also successfully developed a technique for prolonged blood preservation initially by adding gelatine in the blood sample. In 1916, they replaced the additive with a citrate-glucose solution which extended blood storage from one week to two weeks. The use of citrate was the key to the beginning of modern blood transfusion. At the time, blood transfusion was by direct person-to-person so that the preservation method allowed transfusion in the absence of a donor. An English physician Oswald H. Robertson, serving in the US Army, brought the new technique to Belgium in 1917. It became the world's first blood bank. Physiology Rous also made important contributions in the physiology of digestion focussing on the liver and gall bladder. With Louise D. Larimore, he described the conditions leading to liver damage and