In 1905 two different microbes were proposed to fill the vacant role of etiologic agent for syphilis, one, the Cytorrhyctes luis, by John Siegel, the other, Spirochaeta pallida, by Fritz Schaudinn. After gathering and reviewing the evidence the majority of medical scientists decided in favor of Schaudinn’s candidate. In a previous issue Jean Lindenmann challenged Ludwik Fleck’s suggestion that under suitable social conditions Siegel’s candidate could just as well have won acceptance by the scientific community . To refute this counterfactual (...) thesis, Lindenmann presented an asymmetric account of the dispute over the etiology of syphilis. He adopted the view of the proponents that Schaudinn’s spirochete had already been there in syphilitic lesions for centuries, only awaiting the discovery of an appropriate staining technique to be revealed. Here a more symmetric analysis of the episode will be attempted, paying serious attention to the arguments put forward by the spirochete’s opponents, who expatiated on the many possibilities of inadvertently creating artifacts through microscopic preparation and staining. The symmetric account that is presented in this rejoinder thus aims to trace the simultaneous construction of facts and artifacts. It will not, however, resurrect Fleck’s counterfactual thesis. (shrink)