The correspondence between Sir Ronald Ross (1857-1932) and Sir Patrick Manson (1844-1922) is rich in both scientific and human terms. It records, in great detail, Ross's research in India between 1895 and 1899, which elucidated the role of mosquitoes in the transmission of malaria, work for which Ross was awarded the 1902 Nobel Prize for Medicine or Physiology. Ross described the mosquito-transmission theory as Manson's 'Grand Induction', and he had returned to India, where he was an officer in the Indian Medical Service, having been primed by Manson. Ross's regular letters to his mentor document the frustrations and false trails as well as the excitement of discovery. Manson in turn acted as a kind of agent in London, publicising his findings, offering advice and seeking to use his influence to secure for Ross the working conditions he so desired. These 173 letters, plus 85 from the two decades after Ross's return to Britain also record the rise and full of a relationship, as Ross's preoccupation with his place in the history of malariology led to a breach between the two men. Themes of priority, nationalism, and personal vanity punctuate this latter correspondence, which also reveals new insights about the golden years of tropical medicine. Ross included some of the correspondence in his Memoirs, but most of it appears here, fully annotated, for the first time.