that the same bacillus he had seen in Alexandria was also found in Calcutta. Given that India was considered the homeland of the disease, the connection that Koch established between cholera cases in Alexandria and Calcutta was considered a major breakthrough and a powerful mechanism by which to convince the public that microorganisms were the cause of epidemic diseases. Moreover, India provided fresh cases for the study, since the epidemic was already subsiding in Egypt when both German and French commissions arrived. Yet, locating the microorganism in places where people believed the disease to be endemic was not enough to convince an old generation of physicians in Germany who saw disease causation from a different standpoint.
Koch’s biological understanding of the illness directly challenged the groundwater theory that Max von Pettenkofer developed between 1855 and 1865, which had dominated scientists’ perception of cholera up to Koch’s discovery.20 According to this theory, the disease originated from the fermentation of organic matter in the subsoil which then, under certain climatic conditions, was released into the atmosphere and infected people through the nose and lungs. Contrary to Koch, who believed that the disease could only be transmitted to individuals by ingesting bacteria that grew in contaminated water and the intestines of affected patients, Pettenkofer explained cholera’s communication using ideas about the environment and chemistry that were popular among physicians who followed miasmatic conceptions of disease in general. In his view, the “cholera germ,” whatever it was, needed to be transformed by environmental conditions in order to affect human beings. For Pettenkofer, disease communication was largely determined by seasonal and local conditions as well as the individual’s susceptibility to the disease. He advocated for clean water, fresh air, and sewage disposal.
The climax of this discussion was reached in 1885 when Koch and Pettenkofer met in a public forum where the differences in the tenets of hygiene as practiced in Munich and bacteriology as proposed in Berlin were fully exposed.21 While in Munich scientists gave more emphasis to locality, atmospheric factors, and social behavior in the treatment of a disease, Koch and his followers in Berlin were more concerned with state intervention, isolation, disinfection, and quarantine. The challengers of the germ theory criticized the fact that the theory was unable to answer the basic epidemiological questions of contagion and did not explain how the microscopic organism made its way through the population. For example, why did cholera attack during certain periods of the year? What made a particular place susceptible to the illness? If microscopic germs were the cause of the disease, then what had to take place before they became hazardous?
For Koch, the cholera germ was always pathogenic and did not require any transformation to be harmful. The fact that he found the pathogen in the bodies of people who died from cholera and never in healthy individuals made him conclude that the cause could only be the bacterium. However, this discovery alone did not satisfy many members of the medical community who saw the disease as deeply ingrained in the environment, and the dispute over how the disease was communicated and the best methods to combat it continued for several years. In Germany, these disputes persisted until Pettenkofer’s methods were totally discredited in the Hamburg epidemic of 1892 and Koch’s views were imposed in the new Epidemics Bill proposed that same year in the German Empire.22 The germ theory was also institutionalized through the establishment of bacteriological institutes and research facilities all over Germany in the 1890s. These included the Royal Prussian Institute for Infectious Diseases in Berlin (1891), where Koch served as director until 1904, the Epidemiological Institute (1892), and the Institute for Maritime and Tropical Diseases (1900) in Hamburg, and the Royal Hygiene Institute (1899) in Posen, just to mention a few.23
One major challenge cholera posed to Koch over the years was that, contrary to other diseases he had studied, most notably anthrax and tuberculosis, cholera could not be reproduced by the inoculation of the bacillus into healthy animals. This was one of the main conditions he had stipulated for determining the etiology of a disease in his famous postulates.24 Relying on this limitation as an ultimate recourse with which to refute the germ theory after his failure in the Hamburg epidemic, Pettenkofer decided to swallow a pure culture of cholera bacilli on October 7, 1892.25 Rudolf Emmerich, one of his students in Munich, repeated the experiment some days later. Neither of them died from it: Pettenkofer developed a serious case of diarrhea, while Emmerich suffered symptoms of the disease more severely. Both camps in the debate declared themselves winners, one side for the experiment showing that the germ needed to undergo specific changes in the soil before threatening an individual’s life, and the other for it showing that the bacterium indeed affected these two researchers, even if what they developed was a mild case of cholera.
In the end, Koch’s views prevailed both in Germany and the international sphere. His scientific methods were more effective during the epidemic of the 1890s, and the empirical evidence he derived from his studies in Egypt and India gave him the authority to question the groundwater theory. Koch’s success in changing people’s way of thinking rested in his ability to locate the agent of the disease in its “natural” habitat and construct via experimentation a case for the causal function of bacteria, even when cholera did not quite fit his research model. None of the main representatives of the groundwater theory in Germany had ever traveled to study the disease in colonial settings, despite the fact that they had advocates in other empires and overseas colonies, particularly in Great Britain and India.26 Contagionists and sympathizers of the germ theory viewed Koch’s studies as an enormous step towards conquering one of the main threats that colonial realms and poor classes posed to industrialized societies. Despite this, debates about cholera and its mode of communication persisted in some places even after Koch’s achievements in controlling the disease.27
The contributions Koch made to understanding the mode of infection of cholera brought him great recognition and fame in the German Empire. The rapid acceptance of his methods of controlling the disease is noteworthy, given that the discovery he made in the 1880s was of information already known in the 1850s but which had remained a marginal opinion in the medical field back then. While in 1854 John Snow, a famous British anesthesiologist and hygienist, was the first person to point out that water was the mode of communication of cholera, Filippo Pacini, an Italian anatomist, was the first to isolate the cholera germ, which he gave the species name Vibrio cholerae, in the intestines of dead patients in Florence. Pacini’s studies, which also described correctly how to treat the disease through injecting a solution of water and sodium chlorine, were largely disregarded in Italy. Koch himself was unaware of these findings. But what had changed from 1854 to 1884 that made people support Koch’s ideas about cholera, and why did the miasma theory collapse so quickly in the 1880s and 1890s?
The colonial drive that Germany experienced in the 1870s and 1880s made the germ theory more appealing to a new generation of German physicians who, armed with microscopes and other instruments, sought to explore and discover the secrets of nature and other organisms. Similar to cultures considered “primitive,” diseases were to be conquered and made into a thing of the past—something to learn from in exhibits and hygienic museums. When a disease ravaged populations in the nineteenth century, it was largely attributed to the poverty, ignorance, and uncivilized living styles of people in unhealthy environments. Therefore, physicians’ call for hygienic measures and the betterment of people’s health began to bear resemblance to the discourse of colonial propagandists who wanted to expand the frontiers of the German Empire and perpetuate a more aggressive political intervention of the state in the colonies. Moreover, as I have mentioned earlier, with his multiple travels in his quest against cholera, Koch had demonstrated that the colonial realm—which indeed provided much of the vocabulary and practice of bacteriology, as Bruno Latour and Thomas Lamarre have established in their works—was a fruitful place to study diseases.28 The desire in Germany for overseas colonies paved the way for the acceptance and success of bacteriological views.29 Nationalism and an increasing tendency of the state to interfere in German society, as Richard J. Evans has pointed out, were also significant factors accounting for Koch’s achievements.30
Disease, Acclimatization, and Race
Cholera debates in
