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Disease, Race, and Space

THE MID-NINETEENTH CENTURY saw the advent of experimental science in the German lands. Jacob Henle, an ophthalmologist and pathologist from Bavaria, started this movement in 1840 when he published his work on disease communication, Pathologische Untersuchungen (Pathological investigations).¹ The book is now considered a landmark in the history of bacteriology because in its first part, “On Miasmata and Contagion,” the author anticipated the cause of infectious diseases to be an organic element. For Henle, only “foreign” microorganisms had the ability to multiply and produce afflictions in the body of an individual. His analysis constituted the first modern germ theory proposal in Germany. However, the scientific community rejected Henle’s ideas because his observations were reminiscent of “fantastic” contagious theories from the past, and he was unable to provide conclusive proof that directly connected “germs” with specific diseases.²

Henle was a liberal activist of Jewish background who converted to Protestantism at a young age. As a medical student at the University of Bonn, he joined the student society Burschenschaft, a chapter of one of the earliest fraternities in Germany that inspired democratic and national movements in the early nineteenth century. Although branded as a reactionary in the scientific world, Henle shared the same political commitments of many young physicians around this time. In his work on contagion, he summarized the microscopic investigations that predecessors and contemporaries had made in multiple fields of the natural sciences and sought to bring order into the existing chaos regarding the origin of communicable diseases. He divided diseases into contagious, miasmatic, and miasmatic-contagious. According to Henle, contagious diseases were those that could be transmitted directly from person to person, such as syphilis, scabies, other chronic skin diseases, and hydrophobia. Miasmatic diseases were those an individual acquired from the environment without becoming contagious, such as ague, the feverish state of malaria. For Henle, the great majority of diseases fell into the miasmatic-contagious category because they first developed from the miasma of a particular place and then became contagious as they progressed. He considered that diseases such as typhoid, smallpox, measles, rubella, cholera, plague, dysentery, anthrax, influenza, and many others belonged to this category.

The fact that certain miasmatic diseases became contagious was the main logical evidence that Henle provided to support his theory on the organic origin of diseases. Microorganisms had the capacity of multiplying and existing parasitically in the sick body, which would explain why a disease could originate in one miasmatic place and then affect other healthy environments. Moreover, it was well known that, in the case of infection, the morbid matter increased from the moment it entered the body, and only living organisms had the ability to reproduce. Henle’s conclusions derived from life experiences rather than from laboratory science. He did not have the technology to help him identify specific pathogens. His observations stemmed mainly from studies he made on silkworm disease and smallpox.

The lack of experimental basis and scientific foundation led many physicians to dismiss Henle’s theory as a dead hypothesis that dated back to the Renaissance period, if not antiquity. The interesting part is that the miasma theory which skeptics used to explain disease communication at the time was also highly speculative and as old as Hippocrates. In his study, Henle claimed that miasma sympathizers had not been able to demonstrate where the poisonous matter in diseases came from. Nobody knew whether it belonged to the natural kingdom or not. Moreover, they considered the contagious agent a byproduct of the pathological process. As Henle observed, “‘The miasma,’ they say ‘is a noxious matter, originating externally and mixed with the air, which enters into the body, and produces disease even in infinite quantity, in the manner of poisons. The contagious agent on the other hand is a material which is formed by a disease and which occasions the same disease in others.’”³ According to Henle, contagion originated from the disease and not from external forces. Although the miasma theory could not define the exact origins of poisonous matter, one can see in this discussion how the German sciences were already evolving from the more speculative natural philosophy (Naturphilosophie) to the more definite natural science by beginning to value hard evidence.⁴ Before abandoning their immediate sanitary reforms and turning to another theory, physicians required something more than mere reflections. It took approximately thirty years for Henle’s student, Robert Koch, to produce the experimental techniques that proved germs to be the cause of many infectious diseases.

Henle’s contagionist theories proved significant at the height of migration movements and the colonial expansion the country experienced during the second half of the nineteenth century. This chapter studies the rise and popularization of the germ theory from the perspective of Germany’s colonial drive towards overseas colonies and the Prussian-Polish provinces in the 1870s and 1880s. It analyzes the anticontagionist movement that was prevalent in Europe until the 1850s and 1860s, when the experience of two cholera epidemics (1852–55 and 1865–67) led many physicians to reconsider sanitary methods of quarantine and isolation used to contain the disease.⁵ The chapter looks at debates about cholera etiology sparked by Koch’s discovery of the comma bacillus in 1883. In approaching this controversy, this work pays particular attention to the connections between disease, locality, and race that began to concern scientists as Germany became officially involved in overseas colonialism and physicians became actively engaged in colonial practices abroad and at home. It also examines Koch’s professional links to the Prussian-Polish provinces and the responses Poles gave to experimental science and the series of discoveries that placed Germany at the center of biomedicine and modern scientific developments.

The chapter shows how nineteenth-century medicine, far from being a neutral science, served to influence colonial and imperial agendas. Debates in the medical profession reflected the social and political tensions that went along with cultural transformations experienced in Germany in the 1860s and 1870s. Physicians actively participated in the defining moments of national unification and imperial expansion in German history. They helped shape projects for the new German nation and overseas colonies. Understanding the particularities of diseases and how to control them opened the doors for overt overseas colonialism and tightened national frontiers in the eastern borderlands. At the same time, the establishment of colonies as “laboratories of knowledge” strengthened the experimental movement in the German sciences. However, the emergence of the medical profession did not turn every physician into a state collaborator and enthusiast of an aggressive colonial policy abroad. A study of the period before Robert Koch’s major discoveries on the germ theory helps us to understand better the support that the medical profession gave to the policy of imperial expansion in the second half of the nineteenth century.

Anticontagionism and the Professionalization of German Medicine

Up to the late 1860s, anticontagionism was a powerful movement throughout Europe. Medical historian Erwin Ackerknecht claims that it originated in the last decades of the eighteenth century with debates over yellow fever and the ongoing frustrations physicians experienced in trying to contain this disease in colonial realms, the United States, and Europe.⁶ The first anticontagionists were physicians in the English-speaking world, especially in the United States, and the last to convert to contagionism and the germ theory were members of the British medical service in India.⁷ As states in east and central Europe failed to control the cholera epidemic of 1830–1831 by using antiquated methods such as quarantines and cordons sanitaires, the anticontagionist movement grew in influence and gained more followers. Far from stopping the spread of the disease, as many have observed, these techniques only served to exacerbate the poor conditions of people everywhere, contributing to one of the main factors that triggered a series of revolutions across Europe.

In Ackerknecht’s work, anticontagionism is portrayed as a broad trend in Europe associated with the rise of liberalism. Although the author has been criticized for delineating a too-simplistic, dichotomous model of scientific ideas without exploring possible intersections between the two camps, his analysis, delivered in 1947 to the American Association of the History of Medicine, remains a powerful statement on social medicine and the relationship between physicians and political agendas. More specifically, while some historians have criticized Ackerknecht for not taking into consideration specific national contexts, others have claimed that his description, aimed to be transnational, follows too closely the German model.⁸ Following the course of German history, anticontagionism is then defined as a set of liberal political and economic values whose decline came about “after the failed revolutions of 1848 and the German unification ‘from above’ in the 1860s.”⁹ However, by pointing out the common goals of anticontagionists, Ackerknecht was able to transcend the national framework and make fruitful connections among different countries, liberal goals, and leading physicians.

In Germany, one of the main opponents to Henle’s contagionist views was his colleague Rudolf Virchow, who was also a famous liberal activist and pathologist. Virchow disagreed with the germ theory mainly because he believed that the cause of any affliction was not found outside an individual’s body. He ascribed the occurrence of pathologies to local disturbances of the cells. For him, a cell was not only the unit of life; it was also the pathological site.¹⁰ In his view, diseases were to be understood as mere alterations inside the organism of normal bodily processes. He also rejected Henle’s idea that an illness affected the body through the nerves and thought that attention should be directed to other anatomical parts too. Virchow’s major concerns at the time were democratizing the medical profession and making the field more scientific. Henle had similar goals, and throughout his career he advocated for freedom of thought in medicine. He wanted to open a space for theory and observation—which he termed “rational medicine”—in a profession that was becoming increasingly materialist. Despite their differences in approach—contagionist and anticontagionist—both Henle and Virchow were leading representatives of the new experimental turn in science that began to dominate the medical profession at a time when a new generation of German intellectuals was also considering different projects of national unification.

The rise of the medical profession in the 1830s and 1840s coincided with political and social revolutions that mobilized a young generation of German scholars with the goal of strengthening their voice in the political purviews of the German lands. Given that illnesses and treatments are constructed culturally as well as biologically, one can consider the different theories that connected diseases to the body as another form of continuing discussions about the relationship between an imagined German nation and the outer world. Whereas Henle emphasized connections of the individual body with popular mobility and other organisms in nature, Virchow underlined internal developments, local approaches, and environmental improvements. As Virchow expressed in 1848, “Everything political that we’re now doing, the whole constitution, is only the structure through which social reform will come into being, the means by which the conditions of society will be transformed right down to their foundations.”¹¹ In this context, being anticontagionist was another aspect of being a social reformer and a critic of state authoritarianism. Anticontagionists questioned old draconian state measures, such as quarantine and isolation, that had failed multiple times in containing cholera and plague epidemics. Instead of controlling contagious diseases, these measures had only served to aggravate illness among the general population. Hunger, poverty, and filth were seen as the main causes of disease.

According to Ackerknecht, during this period anticontagionists throughout Europe were not merely scientists; they were also social and political reformers who fought for individual rights and commercial freedoms.¹² Many of them were liberal physicians concerned with local and environmental improvements that ranged from cleaning the streets and teaching personal hygiene to canalizing rivers and installing new sewer systems. For them, these sanitary measures seemed to have better effects on the health of any given community than submitting individuals to quarantine ordeals. In Europe, anticontagionism seemed to go hand in hand with revolutionary and progressive ideals. However, while in the German and European contexts these medical views were used to safeguard individual rights and advance developmental and hygienic programs, in the colonial realms environmental approaches and miasmatic explanations served to underscore the fundamental sanitary differences between temperate and tropical zones.¹³ In colonial settings, miasmatic theories tended to identify natives with their natural environment in pessimistic and deterministic ways.

It is within this cultural and political context that one should understand the initial rejection of the germ theory in Germany. Although Virchow’s approaches were useful in the years leading to unification, Henle’s views made a successful comeback in the 1870s and 1880s as physicians began to work closely with the German Empire and demanded an aggressive colonial policy abroad. Without leaving behind the sanitary revolution of anticontagionists in earlier decades, a new generation of physicians went on the offensive against dangerous microbial intruders. As Baldwin observes, “bacteriologists and sanitationists could readily agree that unhygienic conditions promoted the spread of disease, even though the latter saw filth itself as the generator of disease, the former regarding it mediately as a condition favorable to propagating the microorganisms ultimately responsible for illness.”¹⁴ Although debates about disease etiology, which in Germany continued well into the 1890s, tended to separate the two camps, bacteriologists did not break away from the long tradition of sanitary and hygienic measures used to transform the environment. Protecting the “soil” against diseases was a metaphor used both for humans and for localities, usually generating similar disinfection responses.

In the 1860s, discussions about the microscopic world began to appear in Germany in the works of Ferdinand Julius Cohn, a Jewish botanist from the University of Breslau; Ernst Hallier, a German botanist from the University of Jena; and Karl Wilhelm von Naegeli, a Swiss botanist from the University of Munich. The main debate at the time was over whether or not bacteria could be classified into different groups with their own distinctive physiological and morphological features. Cohn was the main proponent of the taxonomic classification of microbial life. Other scientists believed that fungi, molds, and yeasts were all different stages of a limited number of fungal entities that changed according to environmental conditions.¹⁵ To ensure experimental success in the classification, bacteriology had to rely on techniques for the isolation and creation of pure cultures that helped identify the variability and pathogenic factors of microbes. The language that bacteriologists started to use reflected the politics of cultural struggle and the ethnolinguistic definition of German nationalism that began to dominate the public sphere in the 1870s and 1880s.

The rise of bacteriology and germ theory also coincided with the cultural and political establishment of the medical profession. The expansion of health care programs for poor and working-class people, along with the construction of hospitals and other public health facilities, had increasingly strengthened the position of doctors in German society. This medicalization process, in the Foucauldian sense of the word, began to happen in Germany before many other European countries.¹⁶ Since the end of the eighteenth century, different German states had become involved in the supervision of the sick and the regulation of medical practice. If during the 1830s and 1840s many members of the medical profession took an antistate stance, by the second half of the nineteenth century physicians trained in universities and state-sponsored institutions actively participated in the pursuit of the goals of the German nation and empire. Robert Koch became one of the best examples of this transformation in the German medical school.

Robert Koch and the Location of a Disease

In 1883, Robert Koch, one of the founders of the germ theory and perhaps the most influential physician in the late nineteenth century, joined the German Cholera Commission to study the disease in Egypt. An outbreak of cholera in North Africa had gained the attention of authorities throughout Europe, and a group of French and German researchers were quickly mobilized to Alexandria in search of ways to contain the threat.¹⁷ While political disturbances assailed the city and the rest of the Egyptian provinces, Koch found himself in a scientific struggle with both French and British physicians regarding the etiology of an illness that had played a significant role in the establishment of international sanitary regulations throughout the nineteenth century.¹⁸ For the first time, German authorities decided to send experts to other empires’ overseas colonies—first Egypt and then India—to examine a disease with the explicit aim of protecting people at home. For Germany, winning this battle against cholera represented yet another victory with respect to the French, and a powerful assertion of Germans’—particularly Koch’s—views in the realm of hygiene and epidemic diseases.¹⁹

The struggle was also fought at home, where the first cholera conference took place in July 1884 in Berlin, just a few months after Koch discovered 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 the 1880s were symptomatic of a major transformation in the medical field with important consequences for the German Empire. By showing that diseases were caused by pathogens, which could be studied under the microscope, and not by the climatic conditions of a determined place, Koch and other bacteriologists were giving the German state the tools to expand the empire into overseas colonies. This was crucial at a time when some thinkers in the medical and anthropological fields were still stressing the inability of Germans to survive in the tropics. One of them was Rudolf Virchow, who in 1885 delivered a lecture on acclimatization at the annual Assembly of German Naturalists and Physicians (Versammlung der deutscher Naturforscher und Ärzte) in direct reaction to Bismarck’s colonial policy and against an evolutionary theory that he called the cosmopolitanism of people (Kosmopolitismus des Menschen), which was particularly popular among Dutch anthropologists.³¹ This view proposed that all humans shared a common origin and elementary biochemical processes that made them able to adapt to any region in the world after a period of adjustment.³² Koch and a group of young researchers who favored the expansion of the German Empire appropriated this cosmopolitan principle to assert that the best elements of Europeans could be settled in the tropics without having to perish there.³³

Virchow did not believe in the quick acclimatization of any racial group migrating from one natural environment to another. In the annual assembly, he argued that northern Europeans could never adapt to African climates and defended the Lamarckian view, which stated that acquired characteristics could pass from one generation to another.³⁴ His ideas were directed against Germany’s acquisition of overseas colonies and intended to respond to a lecture delivered earlier at the convention by August Weismann on his new theory of the continuity of the germplasm.³⁵ Weismann’s theory proposed that reproductive cells, which he called “germ cells,” transmitted hereditary information without the influence of any somatic cells and independently from anything the body learned in the environment. According to the germplasm theory, acquired anomalies could not be transmitted to descendants when a pathological process had produced them. In Weismann’s words, “An organism cannot acquire anything unless it already possesses the predisposition to acquire it: acquired characters are therefore no more than local or sometimes general variations which arise under the stimulus provided by certain external influences.”³⁶ However, these variations could not be transmitted from one generation to another. According to Weismann, only the predisposition could be passed down to the progeny.³⁷ In light of this theory, diseases were not considered an intrinsic part of the human physiological development, but were viewed as “accidents” in human nature. Therefore, pathology was not considered a proper science but a study of all accidental causes acting upon human beings that changed their normal conditions in a lifetime. The only way diseases could be inherited was when they were congenital—not microbial—and directly affected the germ cells.

Virchow criticized Weismann’s position because it proposed a division between the fields of pathology and physiology when a clear line separating the functions of the two could not be established. He was skeptical of the germ theory for the same reason, and, in his opinion, “Diseases have no independent or isolated existence; they are not autonomous organisms, not beings invading a body, nor parasites growing on it; they are only the manifestations of life processes under altered conditions.”³⁸ A disease occurred when “chemical or mechanical changes” took place in an individual’s cells. The role of pathology was to understand this structural modification of body tissues. Therefore, given this interdependency between physiology and pathology, he considered that all variations within a species, even racial ones, were pathological or a manifestation of the altered condition.³⁹ He claimed that variations at first looked accidental, but they became the norm through inheritance. Virchow dismissed any explanation concerning people’s descent, like the one Weismann was proposing, as highly speculative and lacking empirical evidence. He opposed Darwinism and considered human beings deeply connected to their cultural and physical environments. For him, the white race was composed of different members, the “Aryans” and “Semites” being the two most striking poles.

Contrary to what colonial propagandists were proposing about the superiority of northern Europeans in the tropics, Virchow believed that the best colonizers were Jews, who he thought could undergo acclimatization more easily than the so-called Aryans, given their long history of migration and colonization. According to him, the Phoenicians were the first colonizers they knew of and were Semites who had colonized a great part of southern Europe.⁴⁰ Among the Aryans, he identified those living in southern Europe as having greater potential to adapt to warm countries, not necessarily because of their proximity to the tropics, but because of their racial mixture with Semitic elements. When comparing the colonizing projects and the settlement of Europeans in the Antilles, Virchow established that the Spaniards had been more successful than their French and British counterparts in the region. This success was to be correlated with the level of racial assimilation these people had with Jews, since experience had shown that Jews were best suited to migrate to foreign lands and form permanent colonies.⁴¹ In the realm of German overseas expansion, Virchow believed that racially pure Aryans were weak and vulnerable for the tropics, and there were only few temperate zones in the world where they could be settled at the end of the nineteenth century. The tropics and subtropics were useful for Germans mainly as research stations where the study of many dangerous diseases could be undertaken.⁴² Virchow considered that, before sending people to die abroad, the conditions and options for acclimatization needed to be further investigated.

Considering this gloomy picture that Virchow and other medical anthropologists were painting for ethnic Germans, and given the population growth the empire was experiencing at the time, it is not difficult to understand why the state decided to embrace instead the work that came from experimental biology and bacteriology. These disciplines provided the solution for the settlement of Germans and the expansion of the German nation in warm climates. While Virchow believed that racial miscegenation was the only solution for the survival of northern Europeans in tropical colonies, Weismann gave the answer that people could survive in the tropics without transforming their racial constitution. Around the same time that evolutionary theorists were arguing that the environment did not determine people’s race and that Aryans had the power to overtake nature, Koch and other physicians were proposing that infectious diseases were caused by microorganisms that could travel anywhere according to epidemiological evidence. This biological proximity between the “cosmopolitanism” of human beings and bacteria and the tensions between race and space redefined in important ways the cultural and political relations among Germans, nonethnic Germans, and subjects in the tropical world. The main question at stake in discussions about diseases and acclimatization was, of course, racial degeneration. In Virchow’s work, the environment, by way of diseases, had the potential to degenerate an imagined “pure” German race, and only racially mixed people could resist such degeneration in the colonies. In Weismann’s theory, it was precisely miscegenation that produced racial degeneration. Yet, even Virchow’s idea of miscegenation could be viewed as racist because his anticolonial stance was based on the premise that northern Europeans should not be settled in overseas colonies due to racial degeneration.

Both the germ theory of disease and the germplasm theory of inheritance helped eliminate two significant fears people had about overseas expansion. One was the belief that diseases in the tropics were undefeatable and the other was the notion that Germans could “go native” in overseas colonies. With appropriate measures to control both miscegenation and infectious diseases, Germans could be settled in overseas colonies without having to give up their Germanness. In addition, the theories brought important transformations in the practice of colonialism, in the way physicians interacted with patients, and in the mode in which individuals related to the state. For colonialism, the introduction and institutionalization of these two theories meant that the colonial state began to rely more on experimental science and medical expertise, replacing the local knowledge provided by indigenous populations, on which earlier forms of European colonial expansion depended so much.⁴³ Relations between doctors and patients in Germany were also affected in the sense that the knowledge obtained in the laboratory took priority over patients’ own descriptions of the condition. The theories also gave power to states to introduce regulations that controlled individuals’ personal choices and behaviors in the name of the greater well-being of the nation-state.

Carl Flügge, head of the Department of Hygiene at the University of Breslau, gave a good description of the significant role that experimental science began to have in German medicine in his study of the spread of diphtheria in Breslau from 1886 to 1890. In this work, the author celebrates the fact that experimental approaches to diseases, contrary to previous medical observation and statistical methods, had led to more effective and accurate knowledge of the sources of contagion.⁴⁴ The discovery in 1884 of the diphtheria bacillus by two German bacteriologists, Edwin Klebs and Friedrich Löffler, had enabled people to artificially recreate the conditions of the illness in the laboratory and uncover the peculiarities of the pathogen and its mode of communication. In 1890, these studies culminated in the creation of a serum therapy developed by Emil von Behring, Erich Wernicke, and a Japanese bacteriologist, Kitasato Shibasaburō, who was trained by Koch in Germany. According to Flügge, only experimental science could lead to a successful understanding of the disease. Previous methods used in its study were inefficient mainly because “it was difficult to obtain reliable statistical material either about diphtheria or the cases of death produced by it in larger areas and groups so that the natural variations in the ways in which the illness was spread could be associated with different possible factors.”⁴⁵ One of the main goals was to find specific causes, and it was rather challenging to establish the origins of infection just by looking at diseases from a statistical point of view. Flügge was proposing to move away from epidemic studies whose explanations of the disease were too strongly attached to climatic conditions and place of incidence. He believed that whenever people moved to a new locale, they brought with them their “lifestyle habits and peculiarities” and the same risks and dangers of the illness.⁴⁶

Even though the new ways of defining disease and laws of inheritance introduced at the end of the nineteenth century could be interpreted as more liberalizing and less deterministic from a theoretical point of view, they turned out to be even more restrictive, since they gave additional power to doctors and authorities to interfere with individual and communal living styles. The notion that diseases were not determined by climatic and geographic conditions but by “cosmopolitan” bacteria did not translate into an equal treatment of populations regardless of the place, ethnicity, and racial group they belonged to. As many scholars have pointed out, microorganisms, carried by vector hosts, became identified with different groups in society and came to be seen as political and national threats.⁴⁷ John Farley argues that in the colonial realm the germ theory helped create policies of racial segregation in which the natives themselves replaced the tropical climate as the major threat and were seen as the source of life-threatening germs.⁴⁸ Moreover, people began to believe that an individual, even when not suffering from an illness, might carry the predisposition to acquire the disease from previous generations.