Modern categories of citizenship and discourses of nationalism are inconceivable without the existence of two inventions: the microscope as a laboratory instrument and the statistical concept of normality. The former, first devised by Dutch opticians around 1600, was the sine qua non of the bacteriological revolution spearheaded by Robert Koch and Louis Pasteur beginning in the 1870s.Roy Porter, The Greatest Benefit to Mankind: A Medical History of Humanity (New York: W. W. Norton and Company, 1997), chs. 9, 14. On bacteriology in the United States, see George Rosen, A History of Public Health (Baltimore: Johns Hopkins Press, 1993 [1958]), chs. 7, 8 and John Duffy, The Sanitarians: A History of American Public Health (Chicago: University of Illinois Press, 1990), ch. 13. The latter had been christened several decades earlier by Adolphe Quetelet when he prestidigated the mean or “average man” by plotting the chest circumferences of over 5,000 Scottish regiment soldiers and calculating basic frequencies. Soon, the idea of normal distribution became a cornerstone of the emergent fields of sociology, anthropology, demography, as well as the insurance industry.The social, philosophical, and mathematical epistemologies which generated the concept of normality have been deftly analyzed by Ian Hacking. See his The Taming of Chance (New York: Cambridge University Press, 1990). Also see Theodore M. Porter, The Rise of Statistical Thinking, 1820–1900 (Princeton: Princeton University Press, 1986). In different but interconnected ways, each invention opened up an extensive and untraversed terrain of corporeal and organic knowledge which it alone was capable of deciphering. Guided by the logic of germ theory, scientists used the microscope to translate invisible pathogens into classifiable bacilli and facilitated the manufacture of large-scale cures such as anti-toxins and vaccines. If the microscope and its appurtenances of slides and cultures exposed a hidden bacterial world which had previously existed only in the abstract, statistical methods and normal curves inductively abstracted from the concrete “to a postulated reality,”Hacking, The Taming of Chance, 109. originating prototypes and endowing them with enough distributive power to stand for the whole.