The spirometer is used routinely to diagnose respiratory disease in specialist and primary care settings, although most patients probably do not recognize the name of the device. An important feature of spirometry is that numerical values produced with the device are routinely “corrected” for race and sometimes ethnicity. The “correction” factors for race and/or ethnicity are embedded seamlessly in the software and hardware of the spirometer, such that operators are generally unaware of the details of the correction process activated when they use the machine. The basis of this practice dates to Civil War anthropometrists and plantation physicians who reported lower lung capacity in blacks as compared to whites. This book explores the production of scientific ideas about the “vital capacity” of the lungs and social ideas about racial and ethnic difference from the mid-nineteenth century to the present through the mediating mechanisms of the spirometer. For reasons that this book examines, a century and a half of research investigations have converged on the idea that people labeled black – and most other groups worldwide – differ in the capacity of their lungs from people historically labeled white/European/Caucasian. Explanations for difference varies but notions of innate/genetic difference continue to shape the biomedical literature on lung capacity. If anything, the advent of genomics has brought a reinvigoration of ideas of innate difference in current research. Race correction continues to the present day.