Internal Rotation(s): Sociomaterial Practices and Embodiments in Hugo Sellheim's Experiments on Birth Mechanics.

At the turn of the twentieth century, in the midst of a shift in obstetrical research toward physiology, German obstetrician Hugo Sellheim (1871-1936) embarked upon a research project on the laws of birth mechanics. In a comprehensive experimental program, centering on the internal rotation of fetuses during birth, he tried to find out what kind of mechanical and expulsive forces were at work in the birthing process. From these experiments emerged a wealth of objects such as anatomical models, mechanical dolls, measuring devices, new physical instruments, and also birthing machines. By paying close attention to these objects and the sociomaterial practices associated with them, this article identifies, tracks, and characterizes the shift to physiology in obstetrics. By adopting a historical-praxiographic method, the article reveals the entanglement between the social and the material and renders visible a new and wider set of actors and relationships that, in turn, adds a novel dimension to the historiography of obstetrics.