Introduction: More Than Just a Hand

History has a habit of casting its light on the names it deems worthy, leaving the rest to dwell in shadow. Wilhelm Röntgen, the discoverer of the X-ray, is such a name—illuminated in textbooks, immortalized in plaques, celebrated in the annals of science. But in the soft penumbra just beyond that light stands another figure: Anna Bertha Ludwig, the woman whose hand, offered without hesitation on a winter night in 1895, became the first human subject in a discovery tha...