ArgumentThe experimental development of a therapeutic serum against diphtheria between 1891 and 1894 was characterized by a scientific competition that pitted Emil Behring from the Institute for Infectious Diseases in Berlin against Émile Roux and Elie Metschnikoff from the Pasteur Institute in Paris. In general, their competition can be regarded as an extension of the fundamental differences that separated the research schools of Robert Koch and Louis Pasteur. However, to characterize the competition for a diphtheria-serum as “national rivalry” fails to (...) account adequately for the mutual adoption of experimental practices by the Berlin and Parisian protagonists, whose contributions to the development of a therapeutic serum were intertwined in complex ways. Nor can it be characterized as “cooperation,” given their fierce public disputes over scientific concepts and the fact that these disputes also shaped the peculiarities of the experimental procedures in Berlin and Paris. A close analysis reveals a complex picture of the dynamic interaction between the conceptual and experimental activities of Behring, Roux, and Metschnikoff – interaction that defined as well as bridged the “French” and “Prussian” experimental systems of diphtheria-serum research. (shrink)