This final chapter is on twentieth-century laboratory research in cholera, the archetypical tropical disease. I will juxtapose laboratory research with epidemiological studies and contest the argument put forward by historians that biomedicine and epidemiology and the introduction of ecological factors in the twentieth century led to a greater holism in medicine. I will argue that in the tropical colonies ecology and epidemiology were as limitative concepts as was the laboratory. I will then explore why, despite these new medical ideas and various developments in the medical sciences, tropical regions continue to be stricken with diseases. This apparently straightforward agenda has complex undertones. Cholera, caused by the cholera vibrio that colonizes the small intestine of human beings, is firmly rooted within the traditions of the bacteriology of Koch and Haffkine. Simultaneously, “Asiatic cholera” was an essential formulation of British medical theories about diseases in the tropics from the eighteenth century that linked local climate and environment with disease. This poses an important question to the understanding of bacteriology in the tropics: why did scientists see the cholera vibrio as a peculiarly tropical problem rather than a universal one. This chapter will show why the idea of home appeared in a more persuasive form in cholera research throughout the twentieth century and how it was established by contrived and tenuous modes.