Brazilian discussions of race between 1880 and 1940 were partly a use of European scientific theory to rationalise the native system of colour discrimination. When scientific orthodoxy turned against ‘race’ between 1920 and 1945, much of the intellectual racism of Brazil also dispersed. Quite rightly, most intellectual histories of race in Brazil stress a disjuncture around 1930. However, from the 1870s onward, and most clearly after abolition, there was also a medical-psychiatric strand to ‘race’ that can be unravelled from the rest of the skein. Part of racial thinking in Brazil reflected the general medicalisation of social thought that began when early-nineteenth-century physicians called for hygienic reforms within upper-class families to protect children from hereditary or environmental contaminations. The Spencerian and Comtean positivist social science that became fashionable in Brazil after 1870 also contributed to medicalisation. It saw society as an organism, and compared the role of the social scientist to the role of the physician: to examine symptoms of disease and propose therapies. From the 1880s through the 1920s, the national ailment that the medicalised social thought of Brazil most often diagnosed, an ailment that connected individual health to national well-being, was degeneration.