Cueto shows that productive tensions between doctors and scientists in Argentina, Mexico, and Peru and their counterparts at US research centers and philanthropies shaped the life sciences in the region. Despite assumptions that countries in the Global South produced science of doubtful quality, and despite institutional and economic obstacles, Latin American physiologists took part in networks of scientific power that dictated distinctive styles of laboratory research and strategies to validate experimental medical science. But physiology lost its comprehensive appeal and fragmented into multiple disciplines following World War II. The Cold-War dictated new agendas of research and validation of academic science as an enterprise that restricted the negotiation of US influences. Cueto tells the story of a complex combination of local, transnational, and international factors where dissonance and negotiation, co-responsibility and individualism, competition and collaboration, all coexisted in the name of science.