Born in Almora, India, Ronald Ross spent much of his career in the Indian Medical Service. Because malaria was a devastating health problem in India, he began to study its cause in 1890. His research on the life-cycle of the parasite which causes the illness was instrumental in the modern understanding that malaria is a mosquito-borne disease.

It had long been thought that diseases were spread by odors, and that malaria was caused by the vapors produced in swamps. In 1880, Charles Louis Alphonse Laveran's (1845-1922) observations that the blood of malaria patients contained the pigmented bodies of parasites suggested an alternative cause. In 1894, Sir Patrick Manson (1844-1922) demonstrated the truth of this observation to Ross and suggested that mosquitos were responsible for transmitting these parasites to humans. Ross set out to investigate the life-history of the parasite and to test Manson's theory.

Progress was slow, but on August 16, 1897, Ross...