The German Genius

immigrating to America) but enrolled in natural sciences, soon transferring to medicine.
    No bacteriology was yet taught at Göttingen but Jacob Henle, the anatomist, did consider the possibility that contagious agents could include living organisms. 7 After graduation in 1866 Koch attended Rudolf Virchow’s course on pathology at the Charité Hospital in Berlin, and his career in some ways mirrored Virchow’s. He volunteered for service as a field hospital physician in the Franco-Prussian War and became interested in archaeology and anthropology. But his successes surely owed a great deal—more so even than in Virchow’s case—to the scale of his microscopic investigations. He installed a laboratory in his own home, where he had an excellent microscope by Edmund Hartnack of Potsdam, plus a number of microphotographic devices, and a darkroom. He began by studying anthrax.
    It had been known for some time that anthrax was caused by rod-like microorganisms observed in the blood of infected sheep. 8 Koch’s first contribution was to invent techniques for culturing them in samples of cattle blood, which enabled him to study the microorganisms under his microscope. He traced their life cycle, identified spore formation and germination. More important, he found that although the bacilli were relatively short-lived, the spores remained infective for years. He proved that anthrax developed in mice only when the inoculum contained viable rods or spores of Bacillus anthracis , publishing his results in 1877, together with a technical paper that detailed his method of fixing thin films of bacterial culture on glass slides, enabling them to be stained with aniline dyes. This made possible the study of their structure by microphotography. Medicine was thus the direct beneficiary of the recent developments in three separate areas—dyestuffs, microscope technology, and photography.
    Koch’s next move was to equip his microscope with Ernst Abbe’s new condenser and oil-immersion system (manufactured by Carl Zeiss), which enabled him to detect organisms significantly smaller than B. anthracis . 9 As a result (using mice and rabbits), he identified six transmissible infections that were pathologically and bacteriologically distinctive. He deduced that human diseases would derive from similarly pathogenic bacteria.
    On the strength of this, in 1880 Koch was made government adviser ( Regierungsrat ) in the Kaiserliches Reichsgesundheitsamt (Imperial Department of Health) in Berlin. He shared a small laboratory with his assistants, Friedrich Loeffler and Georg Gaffky, both army doctors. They were charged with developing methods to isolate and cultivate pathogenic bacteria and to establish scientific principles that would improve hygiene and public health. (Johanna Bleker has shown that it wasn’t until the 1850s and 1860s that German doctors thought of hospitals as places of effective science.)
    Koch played a part in the development of the use of strictly sterile techniques, isolating new disinfectant substances, comparing their destructive action on different bacterial species. 10 He found that carbolic acid was inferior to mercuric chloride, bringing about the “dethronement” of Lister’s “carbolic spray,” and he found that live steam was much better than hot air in sterilization. This revolutionized operating room practices. 11
    In 1881 he turned his attention to tuberculosis. Inside six months, “working alone and without a hint to colleagues,” he confirmed that the disease was transmissible (which not everyone accepted) and isolated from a number of tuberculous specimens of human and animal origin a bacillus with specific staining properties. He then induced TB by inoculating several species of animals with pure cultures of this bacterium. His lecture, to the Physiological Society in Berlin on March 24, 1882, was described by Paul Ehrlich as the “greatest scientific event.” 12 The demonstration of the tubercle bacillus in the sputum was soon accepted as of crucial diagnostic significance.
    In the same year, there was an outbreak of cholera in the Nile Delta. The French government, alerted by Louis Pasteur to the possibility that the epidemic could reach Europe, and told that the cause of cholera “was probably microbial,” sent a four-man scientific mission to Alexandria. Koch arrived just over a week later, leading an official German commission. Within days he had observed colonies of tiny rods in walls