The backlands are a semi-arid region of Brazil, where plague became endemic from the 1930s on. The presentation will follow the construction of opposing explanations for plague endemicity in this region by the Chilean doctor Atilio Macchiavello in 1939–1940 and the Argentinian doctor José Maria de la Barrera in 1957–1960. To Macchiavello, the endemicity was tied to the rat–flea complex, whereas to De La Barrera wild rodents were the real reservoir of plague from which rats became infected. The presentation will argue that both experts considered that the backlands’ semi-arid characteristics explained plague endemicity, as the recurrent droughts forced contact between humans, rats, and wild rodents. Moreover, it will argue that these epidemiological explanations were constructed only thanks to interactions between these two foreign experts with Brazilian doctors and rural communities from the backlands. By showing the backlands rural communities as central to producing medical knowledge, the chapter defuses a longstanding perception, according to which this region was backward and isolated from Brazil and the rest of the world, arguing instead that the region was central to the emergence of new medical knowledge.

History and historiography of the sciences and techniques are not only about what and how we as historians narrate experiences of our own countries but the melancholy (Giner) of academic communities captivated by the historiographical authority manufactured by geopolitical orders of our own times.
For this to account for events and episodes of wider geographies and intense travels, a re-situation of so-called norths and souths should challenge such dichotomy. For this aim, travels remain agents involved in circulating ideas, materials practices and people.
Suggesting hybrid ontologies (Romero de Pablos and Santesmases 2023) as things manufactured by expert hands (Roberts, Schaffer, Dear 2007) in arts and crafts of many kind, includes those silent messages transported by living beings to which no proper voice has been given (Dupré y Lüthy 2011). As Portuondo puts it (2009) when reviewing about Latin America, an anti-grand narrative incorporates the voices of subordinate groups.
We will reflect about the contemporary historiography of the sciences in Spain under Franco dictatorship focused in two fields: nuclear energy and genetics, whose trajectories will be reconstructed as an interplay of local and international negotiations, appropriations and agreements.

This paper investigates the conceptualization of metals as living bodies through a global lens, focusing on the vitalistic interpretations of mercury and its peculiar properties as articulated in diverse mythological narratives. Drawing on sources from Byzantine, Syriac, Arabic, Indian, and Chinese traditions, it examines how these narratives developed and interacted across time and space. While some of these traditions are historically interconnected—facilitated by the translation of texts across languages—others exhibit striking thematic overlaps despite minimal or no documented historical links.
The study probes how artisanal practices, alongside cultural, religious, and cosmological beliefs, intertwine in shaping these conceptualizations, challenging the assumption of unidirectional influence. This approach underscores the dynamic, multilayered exchanges that transcend geographical and linguistic boundaries.
Methodologically, the paper reflects on the challenges and opportunities of comparative approaches within a global historical framework. By analyzing both the similarities and divergences among these traditions, it aims to spark broader discussions about the use of comparative methods in global studies, questioning how these methods might illuminate or obscure the complexities of cross-cultural entanglements. This inquiry ultimately seeks to enrich our understanding of how metals, particularly mercury, have been vitalized and symbolized across cultures, offering new perspectives on the interconnectedness of artisanal knowledge and mythological imagination in the premodern world.