One of the major events in the history of German anti-Semitism has been, if not entirely overlooked, then misunderstood and misrepresented. In the 1870s, the professor of medicine, liberal politician, and anthropologist, Rudolf Virchow (1821–1902), directed a study of the skin, hair, and eye color of 6,758,827 German school children, a study that marked “Jews” and “Germans” as racially different and trained a generation of Germans to perceive these differences both as real and as of political significance. Historians have been virtually unanimous in viewing this study as a blow against anti-Semitism, as a demonstration that there was neither a Jewish nor a German “race.” This interpretation has survived, I believe, because it supports and rests on a commonly held conception of racism as primarily an intellectual phenomenon, as a set of more-or-less explicit propositions held in the minds of individuals. Virchow, a well-known opponent of political anti-Semitism, was never motivated by hostility to Jews in conducting this research. Indeed, he understood his focus on Jews as simply a race (rather than as a religion or a culture) to indicate that the study was not anti-Semitic. Paradoxically, the study that Virchow designed and oversaw may have unintentionally provided an important practical basis for German racial anti-Semitism. By considering anti-Semitism as a set of skills rather than a philosophy, as hands-on practical knowledge more akin to riding a bicycle than to philosophical exposition, I hope to offer a new explanation of both Virchow's study of race and the place of that study in German history.