Robert Koch, who had been a student of Jakob Henle’s at Göttingen, advanced beyond observation and supposition with his experimental work of the 1870s and 1880s, identifying the microbial causes of anthrax, tuberculosis, and cholera. Koch’s discoveries, along with those of Pasteur and Joseph Lister and William Roberts and John Burdon Sanderson and others, provided the empirical bases for a swirl of late-nineteenth-century ideas that commonly get lumped as “the germ theory” of disease,
