Leprosy and the elusive M. leprae: Colonial and imperial medical exchanges in the nineteenth century

In the 1800s, humoral understandings of leprosy successively give way to disease models based on morbid anatomy, physiopathology, and bacteriology. Linkages between these disease models were reinforced by the ubiquitous seed/soil metaphor deployed both before and after the identification of M. leprae. While this metaphor provided a continuous link between medical descriptions, Henry Vandyke Carter's On leprosy (1874) marks a convergence of different models of disease. Simultaneously, this metaphor can be traced in popular and medical debates in the late nineteenth century, accompanying fears of a resurgence of leprosy in Europe. Later the mapping of the genome ushers in a new model of disease but, ironically, while leprosy research draws its logic from a view of the world in which a seed and soil metaphor expresses many different aspects of the activity of the disease, the bacillus itself continues to be unreceptive to cultivation