Nansen studied zoology at the Royal Frederick University, and later worked as a curator at the Bergen Museum where his research on the central nervous system of lower marine creatures earned him a doctorate and helped establish modern theories of neurology. After 1896 his main scientific interest switched to oceanography; in the course of his research he made many scientific cruises, mainly in the North Atlantic, and contributed to the development of modern oceanographic equipment. As one of his country's leading citizens, in 1905 Nansen spoke out for the ending of Norway's union with Sweden, and was instrumental in persuading Prince Charles of Denmark to accept the throne of the newly independent Norway. Between 1906 and 1908 he served as the Norwegian representative in London, where he helped negotiate the Integrity Treaty that guaranteed Norway's independent status.