Chapter 1 demonstrates that the nineteenth-century medical record undermines the idea that each person could have only one sex. Throughout the period, several doctors made a stand for “true hermaphrodism,” many more could not identify the sex of their living patients, and “experts” constantly disagreed not only about findings, but also about how best to establish sex in unclear cases. Precisely because no one method for determining sex proved entirely foolproof, doctors and medical forensics experts often relied on narrative to support their claims – a narrative that closely mirrors the one being developed simultaneously in contemporary fiction, and especially, but not exclusively, by realist fiction. Herculine Barbin’s memoirs (the only extant memoirs of a nineteenth-century intersex person in Europe) find their literary corollary in popular fiction that shares much with the creativity and exploitation of narrative techniques in the medical record. Newly uncovered case studies challenge the longstanding representation of the rigidly polarized binary in nineteenth-century France as well as the Foucauldian thesis of “true sex.” Patients sometimes made their own sex determinations, or sought out multiple doctors in order to meet their needs.