From Nancy Tomes' The Gospel of Germs: Men, Women, and the Microbe in American Life, pp. 23-47.

On a cold, damp day in February 1884, the children of Martha Bulloch Roosevelt were summoned to attend at her deathbed. A few days earlier, Martha, the widow of the prominent New York City philanthropist Theodore Roosevelt, Senior, had developed what had appeared to be a slight cold. As her condition rapidly worsened, her doctor diagnosed her illness as typhoid fever, an often fatal gastrointestinal disorder. Telegrams were sent to her daughter Corinne in Baltimore and to her son Theodore in Albany, urging them to come quickly to their mother's elegant home on West Fifty-Seventh Street. For Theodore, the summons had a second somber purpose: in the same house lay his wife, Alice, who had just given birth to their first child and was gravely ill from a kidney ailment known as Bright's disease. At three o'clock in the morning on February 14, Martha Roosevelt died, surrounded by her children. Alice Roosevelt soon followed, dying in her husband's arms less than twelve hours later. Years afterward, Corinne could recall the words that her brother Elliott spoke to her as she arrived home that night: "There is a curse on this house."

The affluent mourners who crowded the Fifth Avenue church for the double funeral of Martha and Alice Roosevelt must have pondered the "strange and terrible fate," as Theodore put it, that so prematurely took their lives. Martha was only forty-eight and Alice but twenty-two years old. Family and friends no doubt regarded Alice's demise as the more tragic, given the newborn daughter she left behind, yet in one sense it was the more understandable. The rigors of childbirth claimed many women's lives, and one who had an undiagnosed kidney disease, as Alice did, would be especially vulnerable.

Martha Bulloch Roosevelt's death was a different matter. She succumbed to what by the early 1880s had been clearly typed as a "filth disease," that is, an illness spread by fecal contamination. As such, typhoid fever was considered eminently preventable by the practice of proper domestic sanitation. We now know that Martha Roosevelt could easily have contracted typhoid outside tier home from eating contaminated seafood in a restaurant or from coming in contact with a healthy person who carried the bacillus, such as the infamous cook "Typhoid Mary" Mallon. But as of 1884, these modes of infection had yet to be discovered, and public health authorities thought that typhoid spread via defective household plumbing, which tainted air and water with the disease "poison."

At the time of Martha Roosevelt's death, the precise nature of the typhoid poison was in dispute. The majority of physicians thought the disease agent was a chemical substance produced by decaying fecal matter. In contrast, a small but growing number of public health experts believed that the chief danger came not from the fecal matter but from the living microorganisms it contained. In 1880, two German physicians had isolated a species of bacteria, subsequently referred to as "Eberth's bacillus," that they believed caused typhoid fever. The same year that Martha Bulloch Roosevelt died, the New York City Department of Health issued the Handbook of Sanitary Information for Householders, which warned that "the greatest danger ... in the breathing of sewer-air is that of inhaling with it the living particles (bacilli, etc.) contained or developed in the excreta of' diseased persons."

But although experts argued over the causal agent, no one questioned that typhoid fever's appearance in any home should prompt close scrutiny of its sanitary arrangements. Therein lay the mystery of the Roosevelts' tragedy. The mansion on West Fifty-Seventh Street, which Theodore Senior had built in the 1870s, had been designed by the leading architects of the day and equipped with the finest fixtures and appointments. Moreover, Martha Roosevelt, familiarly known as "Mittie," was excessively concerned about cleanliness, to a point that family and friends considered almost obsessive. She moved from rural Georgia to New York City after her marriage in 1853 and was never reconciled to the extraordinary filth of that rapidly growing metropolis. To combat it, Mittie developed a rigorous set of cleanliness rituals, which included bathing daily with two changes of water, putting a sheet on the floor when she knelt to pray at night, and wearing white clothing even in winter so that no speck of dirt could escape her scrutiny. With the assistance of a small army of servants, she kept her home equally pristine. A family friend recalled reading a many-paged set of housekeeping instructions prepared for her daughter-in-law Alice, outlining an exacting regimen of polishing, scrubbing, sweeping, and dusting. For example, each morning the cook was required to greet the ash man with a bucket of boiling water to scald his ash can before it entered the house.

Yet for all these heroic efforts to keep herself and her home spotlessly clean, Martha Roosevelt succumbed to what public health experts knew to be a "filth disease." Such a fastidious woman would surely have died of shame, had the typhoid fever not killed her, to discover that she had contracted a disease spread by fecal contamination. Martha Roosevelt's death from typhoid epitomized the uncertainties that beset even the most conscientiously clean households of the Gilded Age: no one, not even the most careful, seemed to be safe from the invisible agents of disease.

The heated scientific debates of the 1870s and 1880s over the identity of those invisible enemies coincided with a period of intense anxiety about rising disease rates in both the United States and Europe. The mortality statistics collected by municipal authorities confirmed what personal experiences such as the Roosevelts' had suggested-that rates of illness and death had risen alarmingly in the nineteenth century, making large cities very unhealthy places to live. Not only were inhabitants thrown into periodic crisis by recurrent epidemics of diseases like cholera and smallpox, but they were also harried by endemic diseases such as typhoid and pneumonia that killed steadily year after year. The young were particularly at risk: in Martha Roosevelt's New York City, for example, one-fifth of all infants died before the age of one, often of the dreaded "summer complaint," or infant diarrhea, and those lucky enough to survive until adulthood still faced nearly a one in four chance of dying between the ages of twenty and thirty.

As a result, late-nineteenth-century Americans of all classes had an intimate knowledge of ailments that are rarely seen today, even by specialists in infectious disease. They were familiar, for example, with the blue skin and rice-water discharges of cholera and the high fever and rash that signaled typhoid. They could recognize the characteristic skin eruptions of smallpox, and the sore throat, strawberry tongue, and sunburn-like rash of scarlet fever. They could differentiate the coughs associated with whooping cough, pneumonia, and consumption. They knew too well the chronic diarrhea and wasting that indicated the "summer complaint" and the labored respiration and blocked airways produced by diphtheria.

This all-too-everyday experience with disease and death left many urban Americans with a profound sense of dread. Even the "best" households seemed under siege from mysterious fevers and wasting diseases that came and went with little predictability. On the surface, the everyday life of affluent Victorians appeared comfortable and well ordered; compared to their grandparents and parents, for example, Martha Bulloch Roosevelt's generation had achieved an unprecedented degree of gentility. Yet they still fell prey to diseases of uncleanness. This sense of vulnerability created the backdrop for the growing debate over the germ theory of disease, a theory that its advocates felt explained the mystery of why the determined pursuit of cleanliness had failed to protect Martha Roosevelt and her contemporaries.

A World of Unseen Dangers

In an 1880 paper delivered to the San Francisco Medical Society, imposingly titled "On the Supposed Identity of the Poisons of Diphtheria, Scarlatina, Typhoid Fever, and Puerperal Fever," a physician named William H. Mays began emphatically, "I will state at the outset that I am an ardent germ-theorist, viewing any doctrine that conflicts with that theory much as I would an attempt to controvert Newton's law of gravitation." In catechism style, he spelled out the tenets of his faith in these terms:

I hold that every contagious disease is caused by the introduction into the system of a living organism or microzyme, capable of reproducing its kind and minute beyond all reach of sense. I hold that as all life on our planet is the result of antecedent life, so is all specific disease the result of antecedent specific disease. I hold that as no germ can originate de novo, neither can a scarlet fever come into existence spontaneously, I hold that as an oak comes from an oak, a grape from a grape, so does a typhoid fever come from a typhoid germ, a diphtheria from a diphtheria germ; and that a scarlatina could no more proceed from a typhoid germ than could a sea-gull from a pigeon's egg.

Read over a century later, when the germ theory of disease is viewed as a scientific truth on the order of Isaac Newton's law of gravitation or Charles Darwin's theory of evolution (to which Dr. Mays also subscribed), this declaration of faith sounds decidedly strange. Whatever controversies may exist today about the nature of infectious diseases, scientists no longer debate whether the streptococcus responsible for scarlet fever can generate spontaneously, much less turn into the bacillus that causes typhoid fever. But May's litany of beliefs captures precisely what it meant to believe in this new theory of disease when the majority of doctors in Europe and the United States still believed that a seagull could hatch from a pigeon's egg, so to speak.

As of 1880 the majority of Anglo-American physicians found these radical ideas about disease causation hard to accept. The medical world was firm in its allegiance to another explanation, the so-called zymotic theory of disease, which rested on a different set of convictions: that the disease agents were chemical ferments produced by decaying filth, and that they could generate spontaneously given the fight atmospheric circumstances. Moreover, they were more than satisfied with the progress of preventive medicine, or "sanitary science" as it was often called, in suggesting ways that the zymotic diseases might be brought under better control.

Given the widespread satisfaction at the time with the zymotic theory and sanitary science, it is little wonder that advocates of the germ theory expressed their new faith with such bravado. In the 1870s, believing in the germ theory was often likened to a religious conversion. Its adherents referred to themselves as "converts" to the new "doctrine" and presented the tenets of their creed in catechism form, as did William Mays. Like born-again Christians, ardent germ theorists saw the world with new eyes, as a place where air, water, and soil teemed with invisible life and their own skin and secretions swarmed with microbes. As the microscopist Lionel Beale put it, "the higher life is everywhere interpenetrated by the lower life," locked in a microscopic survival of the fittest.

The English word "germ," which derives from the Latin verb "to sprout," had long been used to refer to the intangible "seeds" of contagion. Advocates of the new theory adopted the term to signify any microscopic organism capable of causing human or animal disease. Researchers would eventually be able to distinguish among the larger and more complex organisms, such as bacteria, fungi, and parasites, and the much smaller viruses and rickettsiae. But in the 1870s, the individual agents lumped under the category of "germ" or "microbe" were not so well known, and early expositions of the germ theory employed a bewildering variety of terms to describe them, including "vibrio," "algae," "cryptograms," "microzymes," and "schizophytes."

Conversion to this way of looking at infectious disease required faith in a new mode of scientific investigation. Traditionally, physicians had based their theories about disease on observations of illness in the individual and the community, or what today we would term clinical and epidemiological evidence. In contrast, belief in the germ theory rested on evidence derived from the laboratory. Experimental methods for linking germs and disease began to develop in the 1860s and 1870s, most brilliantly in the work of the French chemist Louis Pasteur and the German physician Robert Koch. For adherents of the germ theory, the evidence that experimentalists gathered from microscopic examinations, test-tube cultures, and animal experiments provided a new kind of divination into the fundamental nature of disease.

But for most of their contemporaries, the new experimentalism seemed little reason to abandon insights derived from decades of clinical and epidemiological observation, insights that supported the validity of the zymotic theory and sanitary science. As a result, from 1865 to 1895 Western medicine underwent a virtual civil war over the truth of the germ theory. In both Europe and the United States, the profession divided into hostile camps that jousted across countless pages of medical journals and textbooks. In the end, advocates of the germ theory triumphed: by the 1890s, medical students were being educated to revere the germ theory as scientific orthodoxy and to regard Pasteur and Koch as heroes.

But in the 1870s and early 1880s, when the new view of disease was first introduced to both medical and popular audiences, it had yet to ascend to that privileged status. Instead, the germ theory was often linked to an ancient and discredited tradition in medicine referred to as the "animacular hypothesis." As its advocates knew well, the proposition that the agents of infection were living beings had a long history. In a widely read 1874 article on the germ theory, Karl Liebermeister noted that "positive indications of such an idea are to be found among the writers of antiquity." In succeeding centuries, observers periodically hypothesized that a mysterious contagium vivum might account for the spread of epidemic diseases such as the bubonic plague.

With Antoni van Leeuwenhoek's invention of a simple microscope in the late 1600s, Liebermeister continued, "some sort of an actual basis for such theories was furnished by the microscopical demonstration of very minute living organisms, invisible to the naked eye." In series of widely reported observations, the Dutch merchant detailed world of microscopic characters, many of which lived in or on the human body, who seemed likely candidates for the elusive contagium vivum. Unfortunately, eighteenth century believers got carried away with their microscopic imaginations. Despite the crudeness of their instruments, they devised elaborate identities and family trees for the different microorganisms and produced detailed drawings of creatures with "crooked bills and pointed claws," which some proposed shooting out of the sky with cannons. It was entirely understandable, Liebermeister observed, "that such fantastic ideas should bring down ridicule upon the whole theory," and the weight of medical opinion turned in favor of an atmospheric theory of infection.

The cholera epidemics of the 1830s revived interest in the contagium vivum theory, especially after the English physicians John Snow and William Budd demonstrated that the disease was spread by water polluted with the bowel evacuations of the sick. In 1840, Budd declared his belief that the cholera poison was a living organism. Still, few of his contemporaries were converted to that view, and Liebermeister noted that of this older generation, the German physician Friedrich Gustav Jacob Henle, writing in 1853, was "perhaps the last who elaborated the theory of a contagium vivum." During the middle decades of the nineteenth century, the zymotic theory of disease held virtually undisputed sway in Western medicine.

Still, many naturalists and physicians continued to study microorganisms. Their ability to do so was greatly enhanced in the late 1820s by the introduction of the achromatic compound microscope, invented by an English wine merchant named Joseph Jackson Lister; the new instrument eliminated the problems of distortion at high magnification that had long hampered microscopic observations. As better and cheaper instruments became available, microscopy became a popular pastime among physicians and lay people in both England and the United States. Their growing familiarity with the microscopic world helped set the stage for the rebirth of the old an . macular hypothesis as the new germ theory of disease.

This metamorphosis began in the late 1850s and early 1860s with the work of Louis Pasteur. At first glance, it may seem curious that a chemist rather than a physician played the pivotal role in starting a revolution in medical thinking, yet chemistry and medicine had long been intimately related. The zymotic theory of disease was associated with the German chemist Justus von Liebig, whose work had helped popularize the analogy between disease and fermentation. In taking up his research on fermentation, Pasteur knew that his studies had potential significance for theories of disease.

Trained in chemistry at the Ecole Normale Superieure in Paris, Pasteur first established his scientific reputation in the field of crystallography. In the mid-1850s, while teaching chemistry at a university in Lille, a center of the beet-sugar distilling industry, he became increasingly interested in the process of fermentation. Pasteur's microscopic researches convinced him of an observation that his countryman Cagniard de la Tour had advanced as early as 1835: that the agents of both fermentation and putrefaction were different species of living microorganisms. Working with brewers, vintners, and vinegar makers, all of whose livelihoods turned out to hinge on the successful management of these curious microscopic creatures, he became an expert on the applied science of fermentation. Using his microscope to examine cultures grown in flasks of clear broth, he learned to distinguish between microbial species that produced good beer, fine wine, and flavorful vinegar and those that produced nothing but slimy, revolting messes. He discovered that some species were aerobic, or needed air to live, whereas others were anaerobic and throve in its absence.

Pasteur immediately perceived that his research on fermentation had a significance beyond its usefulness to French industry. The leading medical authorities of the day believed that infectious diseases were caused by chemical ferments, and he had shown the agents of fermentation to be living microorganisms. The implications seemed clear: infectious diseases might be caused by these same microbes. As early as 1859, Pasteur wrote in a paper on microorganisms and fermentation that "everything indicates that contagious diseases owe their existence to similar causes." A few years later, in an 1861 treatise, he suggested that microscopic examination of airborne dust and dirt might provide valuable insight into the spread of epidemics.

Pasteur's work embroiled him in a long-standing scientific controversy over the possibility of spontaneous generation, a debate closely linked to theories about epidemic disease. For centuries, philosophers had debated whether living creatures could originate from nonliving matter. The observation of microscopic life became a central element in the debate; commentators reasoned that if these most primitive forms of being could be generated in sterile flasks of broth, life could arise spontaneously. By analogy, the same reasoning suggested that epidemics could originate de novo-without any connection with a prior outbreak of disease.

In a famous experimental duel with the naturalist Felix-Archimede Pouchet, the most prominent French advocate of spontaneous generation, Pasteur challenged the truth of this ancient doctrine. By an ingenious series of investigations, Pasteur proved that if "ordinary air" (air laden with common dust and dirt) was excluded from contact with a flask of nutritive broth, the broth remained pure and clear. But within a short period of exposure either to unpurified air or to a drop of water filled with microorganisms, the same sterile solution was soon teeming with life. Pasteur suggested that Pouchet and other exponents of spontaneous generation achieved contrary results because their experimental methods were not exacting enough to keep out the ever-present germ matter in the air.

In retrospect, the connections between Pasteur's early work and the germ theory of disease that emerged around 1870 seem obvious. But in the late 1850s and early 1860s, Pasteur was primarily interested in the general problems of fermentation and spontaneous generation, not the specific relationship between microbes and disease. Only in the mid-1860s did he begin to investigate an actual disease, an ailment of silkworms called pebyine; not until the 1870s, after the germ theory of disease had already been articulated, did he start his celebrated research on anthrax and rabies.

Although it is often credited to Pasteur, the modern germ theory disease actually emerged through a far more collaborative sharing of ideas and research. In the 1860s and early 1870s, a small group of natural scientists and physicians, following their own interests or inspired by early reports of Pasteur's work, began to investigate the relationship between microbes and disease. As reports of their work appeared in medical and scientific journals, they gradually came to be seen, and to see themselves, as proponents of a cohesive doctrine regarding the agency of microbes in causing human and animal diseases.

The most numerous group of researchers, which included the French physician Casimir Davaine, the English physician John Burdon Sanderson, and the German physician Robert Koch, used experimental methods to study the process of infection. From blood or other matter extracted from a person or animal suffering from a disease, they tried to isolate the infective agent and then inject it into a healthy animal, a procedure that they hoped would produce the same ailment. By the mid-1870s, experiments of this sort suggested that tuberculosis, diphtheria, septicemia, cattle plague, and anthrax were "inoculable," meaning they could be passed from one creature to another.

The germ theory also gained legitimacy from previous research that had convincingly demonstrated that living parasites caused muscardine, a disease of silkworms, as well as localized skin diseases such as favus and scabies. In the 1850s, investigators showed that an intestinal worm, Trichinellaspiralis, was able to enter the human digestive tract via partly cooked pork, where it reproduced and sent colonies to burrow into other parts of the body. This "new revelation," as one expositor of the germ theory explained, "showed that the whole system, as well as a particular organ or tissue, might suffer from the effects of parasitic contamination." The model of parasitic behavior provided a useful way of understanding the relationship between mirobe and host.

Yet curiously, in the earliest accounts of the germ theory, investigations of actual diseases were often overshadowed by experiments that verified Pasteur's observations about the infective properties of air. Here the work of the English physicist John Tyndall was particularly important in shaping Anglo-American opinion. While conducting research on gases and radiant light, Tyndall became aware of the enormous amount of "floating matter" in the air. Upon reading of Pasteur's work, he became convinced that this matter contained disease germs. To prove it, he did a number of his own experiments and engaged in a long debate with the leading English proponent of the spontaneous generation theory, Henry Charlton Bastian. Tyndall, an accomplished popular lecturer and author, became one of the most important English-speaking advocates of the germ theory during the 1870s.

Another extremely important type of evidence adduced in favor of the fledgling germ theory came not from the laboratory but from the operating room. Like Tyndall, the surgeon Joseph Lister, son of the Lister who invented the achromatic compound microscope, read of Pasteur's speculations about the infective matter in the air and wondered if it might be the source of the postoperative infections that made surgery such a risky enterprise. To neutralize the air's infective properties, Lister began to use carbolic acid as an antiseptic spray and wound dressing; the result was a dramatic reduction in his rates of postoperative infections, Although skeptics claimed that the so-called antiseptic method worked simply because it counteracted the infective properties of the air itself, not the living germs it contained, Lister presented his surgical experience as proof of Pasteur's theory.

The phrase "germ theory of disease," which came into common u se in the English-language medical literature around 1870, was scientific shorthand for propositions associated with the work not only of Pasteur, but also of Koch, Tyndall, Lister, and other investigators. Put simply, the germ theory consisted of two related propositions: first, that animal and human diseases were caused by distinctive species of microorganisms, which were widely present in the air and water; and second, that these germs could not generate spontaneously, but rather always came from a previous case of exactly the same disease.

It should be noted that not everyone who swore allegiance to the germ theory of disease endorsed the second proposition. Many early converts accepted the causal link between microbes and disease while continuing to believe that under the right environmental conditions, disease germs might originate de novo and then spread from person to person. As the British physician Thomas J. MacLagan insisted in Lancet, "That every germ must originate from a pre-existing one may be true; but such a belief forms no essential part of the germ theory of disease." In addition, many early adherents of the germ theory assumed that disease particles required specific conditions to develop, or germinate; thus the disease germ and the mature pathogenic microorganism were not necessarily the same. This assumption was subsequently reinforced by the discovery that some species of bacteria form spores, that is, hardy reproductive cells that under the right environmental circumstances will grow into the mature organisms. Thus there remained considerable diversity of opinion on these points even among professed believers in the new theory.

Early Criticisms of the Germ Theory

As first articulated around 1870, the germ theory was truly a theory, a radical extrapolation from a limited set of experimental observations. Indeed, if one tries to read the early debates over the germ theory impartially, without favoring the side that eventually proved correct, the antigerm theorists appear armed with some formidable arguments. Despite its advocates' appeal to a higher order of experimental evidence, the early laboratory "proofs" offered in favor of the germ theory were few and unconvincing. Even its most fervent advocates freely admitted that essential aspects of the hypothesis remained unproven. Believing in the germ theory, as it was initially formulated from the experimental evidence available in the 1870s, required a considerable leap of faith that most physicians simply could not make.

Objections came not just from poorly educated or marginal physicians, but also from some of the most intelligent, systematic thinkers of the period. Many physicians committed to making medicine more scientific were deeply suspicious of overly simplistic theories of any sort, which they felt harkened back to the sterile hypothesizing of eighteenth-century medicine. Reducing the whole complex origin of an epidemic to the agency of a microbe struck them as a step backward, not forward, in medical thinking. Others objected to the premises of experimentalism itself) To their way of thinking, the behavior of test tube cultures or experimental animals bore no useful analogy to human disease; close observation of many cases of illness provided a much more authoritative body of evidence about the nature of illness. Still others objected not to the validity of laboratory evidence, but rather to its interpretation. Skeptics such as Felix Pouchet and Henry Charlton Bastian fought fire with fire by devising their own experiments to show that microbes could be generated in fluids even after boiling, a process known to kill microorganisms. Particularly in the 1870s, when experimental methods were still relatively crude, the antigerm theory camp could offer experimental results that seemed no less authoritative than those provided by the theory's supporters.

Thoughtful observers also raised a host of objections to the germ theory that could not be easily answered given the available research methods. The very ubiquity claimed for the germ made it difficult for physicians to accept its causal role in disease. Microscopists routinely found many microbial forms on the body and in the secretions of healthy people, so it seemed obvious that the presence of germs alone did not cause illness. As Massachusetts physician Edward P. Hurd remarked in an 1874 review of the evidence for the germ theory, "All the higher organisms seem to be indifferent to them," at least so long as they remained in good overall health.

Moreover, skeptics argued, the growth of unusual bacteria in the secretions of the sick could be the consequence rather than the cause of their illness. The zymotic theory held that when people ingested the chemical ferments of disease, their bodies began to manufacture the by-products of decay that such bacteria needed to grow. As Hurd put it, "There is no proof" that the "lower cryptograms," as he called them, "are not accompaniments, or effects, and not causes of the diseased conditions with which they are found associated." The same problem was raised concerning the animal experiments offered in favor of the germ theory. Early investigators could not easily separate the microorganisms from the blood or tissue of the diseased animal; thus critics argued that some other chemical substance in the inoculated material might have caused the symptoms. As Hurd noted, "It is quite impossible to introduce bacteria into the blood of a healthy animal without at the same time introducing with them septic or putrescent matters which might initiate disastrous changes in the blood, and become the elements of contagion."

Those assumptions about the aerial spread of disease germs common to the early work of Pasteur, Lister, and Tyndall also met with skepticism. If disease germs floated in atmospheric clouds, it was logical to assume that the air surrounding sick people would be heavily laden with distinctive germs. But when investigators sampled sickroom air or exposed microscopic slides to the breath and saliva of patients sick from highly contagious diseases, they recovered microbes that looked no different from those found in their parlors or offices. A Chicago physician who compared the air of sick rooms and ordinary habitations concluded in 1871, "We were unable to detect the slightest particle of any kind in one, which was not equally present in the other."

Moreover, opponents of the germ theory could point to numerous well-publicized cases in which early microscopical enthusiasts supposedly isolated the living agent of a deadly disease from secretions of the ill, only to have the germ in question turn out to be some innocent organism. A case in point was the American physician James H. Salisbury, who claimed in the 1860s to have found the fungal causes of measles, typhoid, malaria, and other fevers. Salisbury developed some ingenious proofs to associate the microscopic palmella plant with malaria; for example, he had volunteers sleep in rooms with boxes of palmella-infused soil on their window sills and observed that they soon fell ill of the fever. Other investigators found it easy to disprove the palmella thesis by showing that it existed in regions that had no malaria. Anticipating Max von Pettenkoffer's famous cholera cocktail of the 1890s, the Philadelphia physician Horatio C. Wood even drank a glass of water infused with the microscopic organism to show that it caused no ill effect.

Salisbury's claims about palmella and malaria represented but one example of many unconvincing attempts to link specific microorganisms with specific diseases. Liebermeister noted regretfully in 1874 that contemporary enthusiasts had done as much harm to the germ theory with their premature claims as their eighteenth-century predecessors had done with their fanciful drawings and cannon shootings. "The utter lack of critical discernment and method which have characterized some of the works in this field, and, on the other hand, the recklessness with which facts of uncertain significance have been proclaimed certain proofs, have also in our time driven away many an earnest investigator," he lamented.

Skeptics like Edward Hurd insisted, quite understandably, that "till, then, more convincing experiments shall have been performed, the poison theory of the older pathologists will hold against the living ferment theory of the newer." He concluded, "In rejecting the Germ Theory as untenable, we have either to confess our ignorance of the causes of all febrile and inflammatory contagious diseases . . . or, guided by analogy, to accept the alternative that the principle of contagion is a subtle chemical ferment, an organic poison, generated in the body of the diseased individual."

The experimental work on anthrax, also called splenic fever, proved crucial to resolving these objections to the germ theory of disease. Anthrax was the first disease that experimenters could convincingly link to a specific microorganism. Primarily a disease of cattle, sheep, and horses that occasionally spread to humans, it caused painful boils, fever, and congested lungs. In 1876, while still a country doctor, Robert Koch identified the Bacillus anthracis, a large and relatively easy to grow rod-shaped bacillus. Using microorganisms cultured in a special medium, in this case the aqueous humor of cattle eyes, Koch showed by repeated experiments that the anthrax bacillus did not exist in the blood of healthy animals but when injected into them consistently produced the disease's distinctive symptoms.

In addition, Koch discovered that the anthrax bacillus had two forms. The mature bacillus, a slender filament, did not survive long after the death of its host, but it produced spores-small, black, seed-like capsules-that were capable of surviving extreme cold or heat. Koch's findings helped to explain why anthrax was confined to certain localities and appeared and disappeared so mysteriously: the anthrax spores remained in the soil and only ripened into maturity under a precise set of environmental conditions. This discovery helped to explain why competent experimentalists could get fermentation in boiled solutions; the heat killed the bacteria but not the hardier spores.

As it turned out, this cycle of bacillus and soilborne spore proved unusual among pathogenic microorganisms; besides anthrax, it was found only in the family of organisms responsible for tetanus, gas gangrene, and botulism. The microbes that caused the vast majority. Of common communicable diseases, including typhoid and tuberculosis, formed no such resilient spores. Yet in the late 1870s and early 1880s, the anthrax model was widely invoked to explain the origin and spread of germ diseases in general. By chance, the first disease causing bacteria clearly identified by experimentalists confirmed the perception that the microbial "seeds" of disease were widely dispersed in the air and soil and required only the right conditions to germinate. The soilborne anthrax spore powerfully reinforced the association of dirt and disease germs. These assumptions, that pathogrnic microorganisms were extremely hardy and widely broadcast in the environment, strongly colored the first generation of preventive strategies advocated in the name of germ theory.

Going Public

Although increasingly sophisticated experimental methods gradually filled in the gaps of what researchers could prove about the germ theory, its advocates did not wait for incontrovertible laboratory evidence before trying to convert others to their views. From the outset of the debate, critics and champions of the germ theory alike actively sought out public forums for rehearsing their arguments. In so doing, they followed a long tradition of "public science" in which even the most elite scientists courted legitimacy by giving public demonstrations of their ideas and experiments. The terminology and style used in these public discourses were far less formal and abstruse than they would become even a few years later. Early commentaries on the germ theory of disease were often delivered in simple language and embellished with colorful imagery that an educated lay person as well as a physician could understand. In the pages of medical journals, in public lectures reprinted for wide distribution, and in magazines such as the Popular Science Monthly, early converts to the germ theory explained the new lessons of the laboratory using everyday experiences of baking and brewing, spoiled food, and dust motes dancing in a sunbeam.

These imaginative modes of describing the microscopic world were particular useful for introducing the germ theory of disease to a wider audience. Well in advance of winning the divisive medical battle over the issue, advocates of the germ theory sought out audiences of mostly middle-class, city-dwelling men and women who took an avid interest in matters of health. In the popular health literature, favorable notices of the germ theory began to appear in the 1870s, when many physicians were still either hostile to or unacquainted with it. Thus the scientific arguments and "proofs" initially offered on the germ theory's behalf were quickly incorporated into popular writings on health and disease.

Explaining the significance of the experiment was an important feature of these early accounts of the germ theory. Although the germ theory's advocates used all sorts of reasoning and evidence to make their case, they presented the laboratory as the source of a new and special kind of knowledge. At the same time, there were relatively few experiments presented on the germ theory's behalf in the 1870s that a serious amateur could not replicate. Early accounts of laboratory life in the writings of such popularists as John Tyndall were a curious mix of the familiar and the awesome. The experimental materials and methods described in them had a homely cast; investigators lovingly recounted how they constructed the air chambers for their test tubes from household materials; prepared culture media from turnips, herring, or beef tea; and warmed their microbial broths over a kitchen stove. (Tyndall once reported that he took a set of test tubes to a Turkish bath in order to incubate them.)

Yet such ordinary, everyday materials as a basin of turnip slices or the juice from a mutton chop produced dramatic results. Commentators used vivid language to describe the bacteria's transformative effects on liquid or solid media: meat or soup initially described as "sweet," "pure," or "limpid" became "slimy," "putrid," or "turbid." One physician experimenter wrote, "My wonder never ceases when I take up one of the flasks and bulbs which have remained barren in my chamber for three or four years, though supplied with air (filtered through cotton-wool) and suitable heat." It was equally amazing, he added, to withdraw the cotton plug and allow the germ-laden dust or water access to the broth: "In a few hours the stillness of years gives place to life and activity."

Experimental accounts also emphasized how one seemingly inconsequential mistake-not rinsing a pipette with sterile water, or failing to sterilize a flask before filling it with the culture medium - could introduce the fertile hordes into a barren environment. By stressing the importance of having an exacting technique, advocates of the germ theory had an all-purpose explanation for why their critics seemed unable to replicate their results: they simply were not careful enough .

Laboratory proofs of the germ theory depended on a willingness to see what happened in the test tube or the experimental animal as a model for what happened in a disease epidemic. The comparisons made were often quite simple. Tyndall pointed out, for example, that the interval of time between introducing the airborne germs to the culture medium and their multiplication into abundant life neatly corresponded to the latency period physicians had long observed between an individual's exposure to contagion and subsequent development of sickness. Likewise, he noted that different broths nourished the germs to different degrees, just as individual constitutions provided more or less resistance to disease. Watching how a hundred test tubes filled with varied infusions of herring and turnip became turbid at different rates, Tyndall observed how "the whole process bore a striking resemblance to the propagation of a plague among a population, the attacks being successive and of different degrees of virulence."

Advocates of the germ theory continually appealed to their audiences to see the parallels between laboratory experiment and everyday observation. As Pasteur's work on fermentation so well exemplified, the insights of the germ theory had much in common with familiar domestic processes such as bread making and beer brewing. In a Glasgow address reprinted in the Popular Science Monthly, Tyndall urged his audience to "observe how these discoveries tally with the common practices of life" and offered examples from his own household, such as his housekeeper's use of brief applications of heat to keep pheasants and milk "sweet." To illustrate the prevalence of germs in the air, he asked his listeners to think about the molds that grew on wet boots or a piece of fruit left exposed to the air and about the dust that appeared in a beam of sunshine after the housemaid cleaned a room. Using his neighbor's efforts to make alcohol from sour cherries as an analogy for the disease process, he explained, "We began with the cherry-cask and beer-vat; we end with the body of man."

Expositors of the new germ theory often struggled to find the right words to describe the "milky way of lower organisms," as the botanist Christian Ehrenberg once called it, that the microscope revealed. First there was problem of terminology; as mentioned before, observers used an exotic array of terms to describe these organisms, such as "monad," "cryptogram," and "infusoria." Individual species had their own strange names such as the "micrococcus" and the Bacillus subtilis. Then there was the challenge of describing their various shapes and movements. Commentators resorted to all sorts of analogies to convey the vagaries of microbial forms: this species resembled a eel, that one a "string of beads," another a "twirling wheel"; their movements across the microscope's field of vision were described as "leaping," "darting," and "springing."

In the Popular Science Monthly, the botanist Ferdinand Cohn, whose scheme for classifying bacteria according to their shape (spherical, oblong, rodlike, and spiral) gradually became the accepted standard, commented on the organisms' antics: "When they swarm in a drop of water, they present an attractive spectacle, similar to that of a swarm of gnats, or an ant-hill." Their patterns of movement were endlessly fascinating. "At one time they advance with the rapidity of an arrow, at another they turn upon themselves like a top; sometimes they remain motionless for a long time, and then dart off like a flash," he observed.

Those who had seen these microscopic marvels continually marveled at how small and fertile they were. In an 1878 lecture delivered to the Philadelphia Social Science Association, the microscopist Joseph Richardson invented some dramatic numbers to convey their minuteness. Disease "spores" were "so small," he wrote, "that 20,000 of them placed end to end, would measure less than one inch in length, and a mass the diameter of one of the periods (.) upon this printed page might contain 50,000,000." Each of these 50 million seeds, he added, was "capable, under favorable circumstances, of reproducing its own kind with almost inconceivable rapidity."

Commentators sought to fit these minute beings into the classifications that naturalists had already developed to describe animals higher up on the evolutionary scale. In their great biological chain of being, microbes occupied the lowest niche as the most "primitive" form of life. They were so primitive, writers often noted, that they reproduced not by the mating of male and female, but by budding, dividing, or producing spores. Their physical structures were remarkably simple-a cell wall enclosing a largely undifferentiated mass of protoplasm-and when not moving, they often could not be distinguished from crystals or other inanimate forms of matter.

In compiling their microscopic bestiaries, early chroniclers divided the microbial world into friends and foes. Much as Victorian naturalists characterized the lion as a noble beast and condemned the wolf as a savage predator, late-nineteenth-century commentators sorted the various species of microorganism into good and bad microbes.

The good species enriched human society, making it possible for people to enjoy bread, wine, and beer, and they played an essential role in breaking down dead matter into elements that could be used by new forms of life. As the American physician George Sternberg wrote dramatically, "But for the power of these little giants to pull to pieces dead animal matter, we should have dead bodies piled up on all sides of us in as perfect a state of preservation as canned lobster or pickled tongue."

Only a few species of "bad" microbes preyed upon humans and animals, yet their potential for creating havoc was impressive. Converts to the germ theory often painted a chilling picture of an environment saturated with these invisible enemies. Bacterial clouds floated about in the atmosphere, carried along by shifting air currents and dropping into the water supply, until eventually they found a receptive media, the human equivalent of the turnip infusion or the beef tea. As Ferdinand Papillon wrote in the Popular Science Monthly, "Our atmosphere ... is the receptacle for myriads of germs of microscopic beings, which play an important part in the organized world." These "penetrating agents of decay, baneful toilers for disease," he observed, "lie ever in wait for the chance to pierce the internal machinery of animals and plants, and create slight or grave disturbances within it."

To describe how germs found a suitable host, germ theorists frequently resorted to comparisons between germs and seeds. Since antiquity, physicians had used the "seed and soil" metaphor, drawn from the New Testament parable of the s describe how the interplay between one's individual constitution and an external disease agent determined one's susceptibility to disease. Exponents of the germ theory found that image particularly well suited for their purposes: the germ or "seed" required suitable "soil"-that is, a weakened constitution - for its full development. The seed and soil metaphor also worked well to underline the specificity of disease agents. Just as a farmer expected to get wheat when he sowed wheat and corn when he sowed corn, the scarlet fever germ only gave rise to scarlet fever and the smallpox germ to smallpox. Nor did the farmer anticipate a crop of wheat or corn to grow where he had sowed no seed at all, as advocates of spontaneous generation had asserted.

Commentators also likened microbes to insects and worms, using the examples of the tiny insect responsible for scabies, or the trichinae worms carried in uncooked pork, to explain the parasitical nature of germs. In a lecture on "the origin and propagation of disease" delivered at the New York Academy of Medicine in 1873, the physician John Dalton developed these examples at some length to help his audience comprehend the unfamiliar world of bacteria and disease. The great potential of the germ theory, he argued, lay in its ability to harmonize with natural science as a whole, "for it will show how large a part of human pathology is connected with the general physiology of vegetative life."

Other expositions of the germ theory used a more feral imagery to describe the microbial parasite. William Mays told his audience that germs "hunt in packs/ and another physician referred to them as "atmospheric vultures.' Microbes were often described in martial terms as attacking, invading, and conquering their human hosts) Joseph Richardson combined both the botanic and feral images in his 1878 speech to the Social Science Association when he explained that contagious diseases were caused by "the transplanting of microscopically visible spores, or seeds, which have a separate vitality of their own, each after its kind, and which are to be escaped, just as we would escape hordes of animal[s], or swarms of insect pests, by shutting them out or killing them before they can succeed in fastening upon our bodies."

The Microbial Survival of the Fittest

Early accounts of the germ theory, with their frequent use of the terms "higher" and "lower" organisms and their references to microscopic predators and parasites, purposefully conjured up images of a microbial survival of the fittest. To a generation of medical and lay readers familiar with evolutionary theory-Charles Darwin's Origin Of Species had been published in 1859, and Herbert Spencer's Principles of Biology had introduced the term "survival of the fittest" in 1861-these were potent analogies. The strong overlap in language between Darwinian theory and germ theory was not accidental. Many of the leading figures in the English debate were committed supporters of Charles Darwin. John Scott Burdon Sanderson was a good friend and frequent correspondent of Darwin. John Tyndall first gained national renown for his defense of evolutionary theory; his rival, Henry Charlton Bastian, also was a Darwinist.

As Bastian's case suggests, professed Darwinians could be found on both sides of the germ theory debate. The implications of evolutionary theory for microbial behavior and vice versa were by no means clear-cut, especially in regard to the vexed subject of spontaneous generation. Still, although advocates of the germ theory had no exclusive claim on evolutionary theory, its growing popularity probably did more for their cause than for their opponents' because the image of a "microbial survival of the fittest" proved to be such a powerful model for the relationship between microbe and host.

At the simplest level, many commentators likened the species of microbes to the distinctive species evident among more complex plant and animal life forms. The popularity in early accounts of the germ theory of adages about seagulls not hatching from pigeons' eggs or horses not foaling donkeys invoked a broader conception of natural law that limited miraculous or unexpected transformations. For physicians intent on making medicine more scientific, this evolutionary perspective on disease had enormous appeal. As Henry Gradle, a professor of physiology at Chicago Medical College, noted, "It eliminates the factor 'accident' from the consideration of disease, and assigns disease a place in the Darwinian programme of nature."

Gradle made explicit the "survival of the fittest" themes that ran through many early accounts of the germ theory. "In the light of the germ theory," he wrote in 1883 in Bacteria and the Germ Theory of Disease, "Diseases are to be considered as a struggle between the organism and the parasites invading it." The contest between microbes and higher life forms was similar to parasitical relations throughout nature in which a smaller species preyed upon the body of a larger creature. He concluded, "We are again ignorant as to the weapons of the contending armies, we do not know yet how the warfare is carried on between the hostile vegetable and animal cells, but that the struggle exists is evident, and it must terminate in the victory of one or the other side."

Although Darwin himself resolutely avoided seeking moral meanings in the workings of evolution, many of his contemporaries observed no such restraint and implied a conscious malevolence to disease germs. Using highly charged adjectives such as "foreign," "base," "murderous," and "cunning," they endowed microbes with a frightening will to destroy their biologically superior competitors. The recognition that "these lowest of created things" worked out their destiny by wreaking disease and death on the human race was both humbling and terrifying.

Yet on the whole, the tone of these early accounts of the germ theory was overwhelming optimistic. Converts portrayed the new discipline of the laboratory as a royal road to safety: by identifying the true agents of disease, their modes of travel, and their sure methods of destruction, the insights of the germ theory would make it easier to outwit the invisible agents of disease. A Philadelphia medical student writing in 1885 captured that sense of optimism, asserting that "after centuries of silent resignation, mankind enlightened by science at last begins to recognize its relentless and hitherto mysterious enemies." He asked rhetorically, "Shall we then continue indefinitely yielding tip the inumerable [sic] victims that yearly succumb to the attacks of foes whose only force lies in their minuteness?" and answered dramatically, "No! Man is no more made to become their prey than that of the wild beasts among whom he had to fight his way in the infancy of the race and whom he has conquered or destroyed by his industry, intelligence, and work."

Paths to Conquest

The most glamorous of these vistas of progress was the potential for discovering new vaccines and drugs. Inspired by the known value of the smallpox vaccination, converts to the germ theory dreamed of devising concoctions of tamed germs that would confer similar protection against other deadly diseases. In the 1870s and 1880s, Louis Pasteur devoted himself to developing vaccines against anthrax, chicken cholera, and rabies. In the 1890s, Robert Koch touted his "tuberculin" as a cure for tuberculosis. Many lesser-known researchers and clinicians experimented with "internal antiseptics," or chemical substances that when ingested would kill microbial invaders.

But from the 1870s to the early 1900s, such hopes were repeatedly dashed. With a few exceptions, such as the rabies vaccine and the diphtheria antitoxin, none of the measures developed in the first flush of enthusiasm for the germ theory stood the test of time. Laboratory scientists continued searching for the fabled "magic bullet," which did eventually materialize-first in the discovery in 1909 of Salvarsan, which cured syphilis, and several decades later in the discovery of sulfa drugs and penicillin.(Yet prior to 1900, the therapeutic promise of the germ theory remained elusive. )

Far more immediate and useful were the insights about hygiene and sanitation derived from the germ theory. Here the apostles of the germ did not have to break such hard, new ground as they did in searching for magic bullets. Early understandings of the germ, which emphasized its ubiquitous presence in air and water and its hardiness outside the body, neatly harmonized with already accepted modes of protection against zymotic disease. As a result, the first version of the gospel of germs represented a surprisingly successful marriage between the old sanitary science and the new germ theory.

That such a happy union could come about was not immediately apparent to the older generation of public health reformers. Such eminent figures as Benjamin Richardson, Florence Nightingale, and Elizabeth Blackwell expressed fears that acceptance of the germ theory would undercut the achievements of sanitary science. They were profoundly uncomfortable with the moral randomness they perceived in the germ theory; if contact with a microbe was the sole cause of disease, then living a virtuous, clean life did not necessarily protect one from its ravages.

In response, early advocates of the germ theory sought to reassure the older sanitarians that the new disease faith only verified the great "truths" of sanitary science. Indeed, for all the controversy that the germ theory engendered in medical circles, its implications for preventive action initially seemed to be consistent with existing tenets of private and public hygiene. In 1873, after reviewing the debates over the germ theory, the president of Columbia University, F. A. P. Barnard, concluded gratefully that when it came to preventive medicine, "The champions of conflicting theories, however freely they may splinter lances in the arena of controversy," could be found "in the face of the common enemy, marching harmoniously side by side."

Certainly when it came to the practice of personal and domestic cleanliness, the new experimental evidence about germs countenanced no slackening off in the zeal required by traditional sanitary science. The reconceptualization of disease ferments as minute living creatures able to replicate in the millions from a single speck only heigh~t3ned the importance of exacting precautions against their spread. Likewise, the anthrax model of bacterial spores capable of surviving high heat and normal disinfectant processes pointed up the need for increasingly rigorous forms of cleanliness.

Pasteur's own reputation for meticulous cleanliness exemplified how acceptance of the germ theory went hand in hand with vigilance to hygienic detail. Having lost two daughters to typhoid fever, he knew intimately the havoc that so-called filth diseases could wreak on a household. Perhaps for this reason, he carried over into his personal life the rituals of cleanliness that he practiced in the laboratory. His son-in-law and biographer Rene Vallery-Radot wrote that whether dining at home or out "he never used a plate or a glass without examining them minutely and wiping them carefully; no microscopic speck of dust escaped his short-sighted eyes." He was "more than difficult to please in that respect," causing him to be a terror to his hostesses. It was Pasteur's long acquaintance with the microbial world that caused him to bring "such minute care into daily life," concluded Vallery - Radot. If a speck of dust could generate a veritable horde of bacteria in a flask of beef broth, what could it do in a soup tureen?

The lore of the laboratory reinforced the point that seemingly inconsequential actions, such as failing to sterilize a flask or a pipette, could bring about rampant germ life. Carried over into everyday life, that mentality pointed toward an even more exacting practice of domestic cleanliness. The practical lessons that advocates of the germ theory derived from the laboratory only underlined the urgency of the sanitarians' warnings that utmost care needed to be taken to evade the domestic sources of disease. Here at last was an explanation for tragedies such as the death of Martha Bulloch Roosevelt. Her rituals of cleanliness had simply riot been precise enough to counteract the depredations of the wily typhoid germ.

The new lessons of the laboratory thus contributed to a widening effort by public health reformers to "pathologize" the home because they invested ordinary behaviors and objects with the capacity to cause or prevent deadly illnesses. Acceptance of the germ theory fed into a revolution in personal and domestic behavior already under way by the 1870s. Commandeering the established truths of sanitary science, apostles of the germ synthesized old and new beliefs about contagion into a new code of protection for the American home. When it came to domestic rituals of purification, the dramatic insights of the germ theory turned out to be so much new wine in old bottles.