Much of the historical literature on tropical medicine represents the periphery as the chief site for the production of western knowledge about disease in the British empire. This study on the Filaria perstans-sleeping sickness hypothesis revises this perspective by showing how the imperial metropole functioned as a culture space for the construction of knowledge about the empire. Beginning in 1891, Patrick Manson used the publicity resources of London to generate a rhetorical imperative for the confirmation of his hypothesis without ever leaving Britain. Later, while he was medical adviser to the imperial state, the 1900 sleeping sickness epidemic in Uganda presented Manson with a unique opportunity to determine the validity of his hypothesis. By exaggerating the possible spread of the epidemic privately among Foreign Office personnel and publicly in the medical press, he succeeded in mobilizing the first Royal Society sleeping sickness research expedition to Africa in 1902. While this expedition ultimately disproved Manson's hypothesis, this outcome ironically created the very conditions for the identification of the actual causal agent (Trypanosoma gambiense) and its vector (tsetse fly) by Aldo Castellani and David Bruce respectively.