Introduction

Stefanie Gänger traces the global rise of thermometry and its numerical thresholds during the late nineteenth century, and the new understanding of fever as internal temperature above 37°C. The article reassembles how a fever was diagnosed prior to the mid-1800s, when it was not reducible to heat, let alone an exactly quantifiable temperature, and recapitulates the invention of thermometry in the city hospitals of mid-nineteenth-century Leipzig and Berlin. It endeavors to explain why these numerical standards could become self-evident facts in many societies around the world over the 1870s and 1880s, from Japan to Peru. It holds that the authority of “38°C” was not simply owing to the unsettling success of quantification, standardization, and “trust in numbers”12 in medicine, but also to the social organization of the medical profession, the period’s imperial order, and gendered epistemic hierarchies.