Testifying before the Indian Plague Commission in 1898, witnesses described the victims of plague: their anxious expressions, su used eyes, parched tongues and suppurating buboes.1 e colonial o cials also described hoards of dying rats: falling from ceilings, staggering out of holes and nibbling on the corpses of plague victims. G. Bainbridge, Surgeon-General for the Government of Bombay, reported to the Commission that it was well known to all with experience with plague that ‘the illness of human beings with plague follows very closely with the death of rats in or about the dwellings’.2 His was one of many voices describing the association of rat mortality with the onset of the epidemic in a neighbourhood. Lt-Colonel S. J. omson reported that for over y years the Government of India had required the evacuation of homes in the foothill villages of the Himalayas, where plague was endemic, at the rst sign of signi - cant rat mortality.3 e Indians themselves had long made the observation that dying rats heralded the onset of the disease and colonial physicians were aware that Hindu texts for a thousand years had advised the evacuation of houses at the sight of dead rats.4 Yet, when the Indian Plague Commission issued its nal report they concluded that Paul-Louis Simond’s theory, that a rat epizootic was a precondition for an epidemic of human plague, was inconclusive and that human agency was the most important factor in the spread of the disease.5 So with rats dying all around them, why did the Indian Plague Commission fail to assign them a primary role in the transmission of the disease? e answer to that question is part of a story that links rats, historians, plague scientists and two separate plague pandemics to tell the tale of the in uence of the Plague Research Commission, which issued its report early in the twentieth century, on the historiography of this disease for the next hundred years.6 However, this is also a story about the seductive power of a one-size- ts-all explanation for a complex

100 Medicine and Colonialism

biological phenomenon and a reminder of omas Kuhn’s argument about the impact of dominant scienti c paradigms on ‘normal science’.7