Between the 1930s and 1960s Puerto Rico was transformed from a marginal United States territory into an industrialised ‘showcase of development’. This article investigates the organisation of milk station programmes on the island during this crucial period and how these reflected the circulation of child welfare knowledge, nutrition expertise and public health practices. During the Depression, these perspectives fostered a recast of the eugenic regeneration ideologies motivating medical assessments of and sanitary interventions with Puerto Rico’s rural poor since the nineteenth century. Innovations in nutrition knowledge and an emerging rural hygiene movement highlighted the negative health effects of the island’s monocrops economy. In this context, the nourishment of children’s bodies assumed symbolic and instrumental significance for the reconfiguration of colonial and developmental models promoted by the new Popular Democratic Party (PPD). The experience of public health professionals in relief work during the 1930s contributed to the articulation of food and nutrition as key elements of this party’s populist discourse. Programmes like milk stations became part of strategies to rear and manage the labour force needed in the industrial development model promoted by the PPD. From the perspective of poor Puerto Ricans, however, they were part of the materialisation of its promise of social justice for the poorer classes.

A pressing question during the first half-decade of the third plague pandemic (1894–9) was what was a ‘suitable soil’ for the disease. The question related to plague’s perceived ability to disappear from a given city only to reappear at some future point; a phenomenon that became central to scientific investigations of the disease. However, rather than this simply having a metaphorical meaning, the debate around plague’s ‘suitable soil’ actually concerned the material reality of the soil itself. The prevalence of plague in the working-class neighbourhood of Taipingshan during the first major outbreak of the pandemic, in 1894 in Hong Kong, led to an extensive debate regarding the ability of the soil to harbour and even spread the disease. Involving experiments, which were seen as able to procure evidence for or against the demolition or even torching of the area, scientific and administrative concerns over the soil rendered it an unstable yet highly productive epistemic thing. The spread of plague to India further fuelled concerns over the ability of the soil to act as the medium of the disease’s so-called true recrudescence. Besides high-profile scientific debates, hands-on experiments on purifying the soil of infected houses by means of highly intrusive methods allowed scientists and administrators to act upon and further solidify plague’s supposed invisibility in the urban terrain. Rather than being a short-lived, moribund object of epidemiological concern, this paper will demonstrate that the soil played a crucial role in the development of plague as a scientifically knowable and actionable category for modern medicine.