This article examines the history of Mexican physiology during the period 1910-60 when two noted investigators, José J. Izquierdo, first, and Arturo Rosenblueth, second, inscribed their work into an international network of medical research. The network had at its center the laboratory of Walter B. Cannon at Harvard University. The Rockefeller Foundation was its main supporter. Rosenblueth was quite familiar with the network because he worked with Cannon at Harvard for over ten years before returning to Mexico in the early 1940s. Izquierdo and Rosenblueth developed different strategies to face adverse conditions such as insufficient laboratory equipment, inadequate library resources, a small scientific community, and ephemeral political support. Both acquired local influence and international prestige, but the sources of financial and academic power remained in the United States. This case study provides insight into the circulation of scientific ideas and practices in an important Latin American country and suggests that the world's circulation of science among industrial and developing nations during the mid-twentieth century was intrinsically asymmetric but opened temporary opportunities for talented individuals and groups of researchers.