Modern history

Tuesday, September 5

ACE BOOKS, NEW YORK

ALL SMELL IS DISEASE

THE FIRST SOLID CAUSE FOR HOPE BEGAN TO FILTER through the neighborhood Tuesday morning. For the first time in four days, Henry Whitehead let himself believe that this terrible visitation might finally be passing. The wife of Mr. G, the tailor, had died that morning, but for every new death, Whitehead could point to another dramatic recovery. The servant woman he had been tending to since Friday had risen from what she had assumed would be her deathbed, her pallor much improved. Two adolescents—a boy and girl—had also turned the corner, much to the delight of their remaining family. All three of them attributed their recovery to one thing: they had consumed large quantities of water from the Broad Street pump since falling ill. The speed and intensity of their recovery made an impression on Whitehead that would linger in his mind through the coming weeks.

In the late-morning hours, a small, formal parade of government officials, the members of the General Board of Health, arrived in Golden Square to tour the scene of the outbreak. The most notable thing about the procession was its leader: the Board’s new president, Sir Benjamin Hall, who had replaced the pioneering but controversial Edwin Chadwick a month earlier, prompting the Morning Chronicle to observe dryly that the incoming president was coming to the job “with one great advantage to his favor—his predecessors managed to accumulate upon themselves so much unpopularity that he has little to fear from invidious contrasts.”

As the officials walked through Dufours Place and Broad Street, small bands of surviving locals appeared on the sidewalk to express their gratitude for the Board’s appearance, their spirits also cheered by the sense that the outbreak was subsiding. The Board’s secretary released an account of the visit to the major papers, most of which obligingly reprinted it, including in their copy the self-congratulatory line: “The Guardians are acting most energetically, and every credit is due to them.” But it was harder to specify what those actions were exactly, however energetic they might have been. The outbreak might have been diminishing, but it was still taking lives at a monstrous clip. More than five hundred residents of the Golden Square neighborhood had died in five days, and another seventy-six had fallen ill the day before. The Times itself was circumspect in describing what the Board was actually doing to battle the outbreak, beyond mentioning plans to form a committee to investigate it. The Board would eventually have a role to play in the Broad Street drama, but for the moment its actions were mostly theater.

The one intervention the Board of Health had made would have been immediately and viscerally evident to anyone walking through the neighborhood: the streets had been soaked with chloride of lime, and the smell of bleach was omnipresent, blocking out theusual stench of urban waste. In this one intervention, Edwin Chadwick’s influence on the Board lingered past his tenure as its head. The lime had been deployed to battle Chadwick’s lifelong nemesis, the sanitary curse he had built a career fulminating against, and the one he would go to his grave believing in: miasma.

IT IS NEARLY IMPOSSIBLE TO OVERSTATE THE IMPACT THAT Edwin Chadwick’s life had on the modern conception of government’s proper role. From 1832, when he was first appointed to the Poor Law Commission, through his landmark 1842 study of sanitation among the laboring classes, through his tenure as commissioner of the sewers in the late 1840s, to his final run at the helm of the General Board of Health, Chadwick helped solidify, if not outright invent, an ensemble of categories that we now take for granted: that the state should directly engage in protecting the health and well-being of its citizens, particularly the poorest among them; that a centralized bureaucracy of experts can solve societal problems that free markets either exacerbate or ignore; that public-health issues often require massive state investment in infrastructure or prevention. For better or worse, Chadwick’s career can be seen as the very point of origin for the whole concept of “big government” as we know it today.

Most of us today accept that the broad movements of Chadwick’s campaigns were ultimately positive ones. You have to be a committed libertarian or anarchist to think that the government shouldn’t be building sewers or funding the Centers for Disease Control or monitoring the public water supply. But if Chadwick’s long-term legacy was a progressive one, his short-term track record, as of 1854, was more complicated. No doubt he had done more than anyone alive to focus attention on the shameful condition of the industrial poor, and to mobilize forces to correct those problems. But some of the most significant programs he put in place ended up having catastrophic effects. Thousands upon thousands of cholera deaths in the 1850s can be directly attributed to decisions that Chadwick made in the decade before. This is the great irony of Chadwick’s life: in the process of inventing the whole idea of a social safety net, he unwittingly sent thousands of Londoners to an early grave.

How could such noble aspirations lead to such devastating results? In Chadwick’s case, there is a simple explanation: he insisted, to the point of obstinacy, on following his nose. The air of London was killing Londoners, he claimed, and thus the route to public health had to begin with removing noxious smells. He expressed this notion most famously—and most comically—in his 1846 testimony to a parliamentary committee investigating the problem of London’s sewage: “All smell is, if it be intense, immediate acute disease; and eventually we may say that, by depressing the system and rendering it susceptible to the action of other causes, all smell is disease.”

WITH FEW EXCEPTIONS, THE PROBLEMS THAT THE EARLY Victorians wrestled with are still relevant more than a century later. These are the standard social questions that you’ll encounter in any textbook account of the period: How can a society industrialize in a humane way? How can a government rein in the excesses of the free market? To what extent should working people be allowed to negotiate collectively?

But there was another debate that ran alongside those more austere themes, one that has not received as much attention in the seminar rooms or the biographies. It’s true enough that the Victorians were grappling with heady issues like utilitarianism and class consciousness. But the finest minds of the era were also devoted to an equally pressing question: What are we going to do with all of this shit?

The extent of London’s excrement problem was universally agreed upon. Chadwick’s influential 1842 study had laboriously recounted the repellent state of waste disposal in the city. Letter writers to the Times and other papers harped on the topic endlessly. A survey in 1849 examined 15,000 homes, and found that almost 3,000 had offensive smells from bad drainage, while a thousand had “privities [sic] and water-closets in a very offensive state.” One in twenty had human waste piling up in the cellar.

Many prominent reformers saw economic waste in all that fecal matter. Using human excrement as fertilizer in the greenlands around city centers was an ancient practice, but it had never been attempted with the waste of two million people. Hyperfertile soils would inevitably result if such a project were carried out, the evangelists claimed. One expert projected a fourfold increase in food production. A proposal in 1843 argued for the construction of cast-iron sewers that would transport waste all the way to Kent and Essex.

Few were as rhapsodic on the subject as Henry Mayhew, who saw in waste recycling an escape route from the Malthusian limits on population growth: “If what we excrete plants secrete—if what we exhale they inspire—if our refuse is their food—then it follows that to increase the population is to increase the quantity of manure, while to increase the manure is to augment the food of plants, and consequently the plants themselves. If the plants nourish us, we at least nourish them.”

As was typical of Mayhew, this circle-of-life philosophizing quickly gave way to a frenzy of numerical calculation:

According to the average of the returns, from 1841 to 1846, we are paying two millions every year for guano, bone-dust, and other foreign fertilizers of our soil. In 1845, we employed no fewer than 683 ships to bring home 220,000 tons of animal manure from Ichaboe alone; and yet we are every day emptying into the Thames 115,000 tons of a substance which has been proved to be possessed of even greater fertilizing powers. With 200 tons of the sewage that we are wont to regard as refuse, applied to the irrigation of one acre of meadow land, seven crops, we are told, have been produced in the year, each of them worth from 6l. [6 pounds sterling] to 7l.; so that, considering the produce to have been doubled by these means, we have an increase of upwards of 20l. per acre per annum effected by the application of that refuse to the surface of our fields. This return is at the rate of 10l. for every 100 tons of sewage; and, since the total amount of refuse discharged into the Thames from the sewers of the metropolis is, in round numbers, 40,000,000 tons per annum, it follows that, according to such estimate, we are positively wasting 4,000,000l. of money every year.

This sort of bookkeeping remained an essential subgenre in the political debate for decades to come. One scholar testified before Parliament in 1864 that the value of London’s sewage was “equal to the local taxation of England, Ireland, and Scotland.” The Victorians were literally flushing money down the toilet—or, worse, leaving it to decay in the cellar.

Edwin Chadwick, too, was a great believer in the economic bounty that lay trapped in London’s sewage. A document he helped produce in 1851 argued that fertilizing the countryside with London’s waste would cause land values to quadruple. He also entertained an aquatic version of the theory, arguing that delivering fresh feces in an expedient manner to England’s waterways would produce larger fish.

But for Chadwick and other social reformers of the period, the primary reason to deal with London’s rising tide of excrement had to do with health, not economics. Not everyone went as far as Chadwick’s conviction that all smell was disease, but most agreed that the vast quantities of waste decomposing in the cellars and the streets of the city were literally poisoning the air. If merely taking a stroll down the sidewalk could overwhelm you with the putrid stench of human waste, something clearly had to be done.

The solution was straightforward enough, at least in theory. London needed a citywide sewage system that could remove waste products from houses in a reliable and sanitary fashion. It would require a massive engineering effort, but a country that had built a national rail network in a matter of decades and spearheaded the Industrial Revolution could handle a project on that scale. The problem was one of jurisdiction, not execution. The urban infrastructure of early Victorian London was governed by a byzantine assortment of local boards that had been assembled over the centuries by more than two hundred separate acts of Parliament. Paving or lighting the streets, building drains and sewers—these were all acts overseen by local commissioners with almost no citywide coordination. One three-quarter-mile stretch of the Strand was overseen by nine separate paving boards. To take on a project as epic as building an integrated metropolitan sewer system would require more than engineering genius and backbreaking labor. It would need a revolution in the power dynamics of city life. The bottom-up, improvised recycling of the scavengers would have to give way to the master planner.

In this, Edwin Chadwick was perfectly cast for the role. Brusque and strong-willed to the point of rudeness, Chadwick was in many ways a Victorian rendition of Robert Moses (that is, if Moses had lost his grip on New York City’s power structure halfway through his career and spent the last thirty years of his life editorializing from the sidelines). A devout Utilitarian and friend of Jeremy Bentham, Chadwick had spent the thirties helping to create—and then, partially, clean up—the national mess that was the Poor Law Acts of 1832–1834. But by the 1840s he had grown increasingly obsessed with sanitation issues, and his crusades ultimately culminated in the passing of the Public Health Act of 1848, which established the three-member General Board of Health, Chadwick at its helm. But the bill with the most dramatic short-term impact on London’s health would be the Nuisances Removal and Contagious Diseases Prevention Act, also passed in 1848, after years of Chadwick’s campaigning. “Nuisance” in this case meant, effectively, one thing: human waste. For a few years, new buildings had been required to drain into the existing sewer system, but the “cholera bill”—as it was conventionally referred to—was the first to require sewer connections from existing structures. For the first time, the law had something to say about people opting to fill their old cellars with “great heaps of turds,” as Samuel Pepys put it in a 1660 journal entry. Though of course the law didn’t quite express it that way—choosing a more delicate, if prolix, language to describe the problem:

[Any] Dwelling House or Building in any City, Town, Borough, Parish, or Place within or over which the Jurisdiction or Authority of the Town Council, Trustees, Commissioners, Guardians, Officers of Health, or other Body to whom such Notice is given, extends, is in such a filthy and unwholesome Condition as to be a Nuisance and injurious to the Health of any Person, or that upon any Premises within such Jurisdiction of Authority there is any foul or offensive Ditch, Gutter, Drain, Privy, Cesspool, or Ashpit, or any Ditch, Gutter, Drain, Privy, Cesspool, or Ashpit kept or constructed so as to be a Nuisance to or injurious to the Health of any Person, or that upon any such Premises Swine, or any Accumulation of Dung, Manure, Offal, Filth, Refuse, or other Matter or Thing, are or is kept so as to be a Nuisance to or injurious to the Health of any Person, or that upon such Premises…

To abide by these new laws, though, you needed somewhere to put all that “manure, offal, and filth.” You needed working sewers. London actually had an ancient drainage system that had evolved around a dozen creeks and small rivers that continue to flow beneath the city to this day. (The largest waterway, the Fleet River, runs beneath Farringdon Road, emptying into the Thames under Blackfriars Bridge.) Parliamentary bills governing the construction of new sewers date back to the days of Henry VIII. Historically, however, London’s sewers had been designed to carry off the city’s surface water. Until 1815, it was illegal to discharge raw waste into the sewers. If your cesspool was overflowing, you called the night-soil men. This system resulted in some foul-smelling cellars, but it left the waters of the Thames remarkably pristine, with a bustling fisherman’s trade working the river between Greenwich and Putney Bridge. But as the city’s population exploded, and as more and more houses discharged their waste into the existing sewers, the quality of the Thames water declined at an alarming rate. What’s more, the sewers themselves began to clog, leading to the occasional underground explosion of methane gas.

Chadwick’s work in the 1840s and early fifties had the perverse effect of exacerbating this problem, both through his position as head of the Board of Health and his seat on the newly formed Metropolitan Commission of Sewers. There was much squabbling and drafting of plans for expanding the city’s sewage system, but nothing practical was done for years, until a brilliant engineer named Joseph Bazalgette took charge of the project. In the meantime, the primary focus was on eliminating cesspools. As Bazalgette would later report: “Within a period of about six years, thirty thousand cesspools were abolished, and all house and street refuse was turned into the river.” Several times a year, the Commission’s engineers would offer enthusiastic reports documenting just how much waste had been extracted from the city’s houses and deposited in the river: 29,000 cubic yards in the spring of 1848, growing quickly to 80,000 cubic yards the following winter. In the space of about thirty-five years, the Thames had been transformed from a fishing ground teeming with salmon to one of the most polluted waterways in the world—all in the name of public health. As the builder Thomas Cubbitt observed wryly: “The Thames is now made a great cesspool instead of each person having one of his own.”

Herein lies the dominant irony of the state of British public health in the late 1840s. Just as Snow was concocting his theory of cholera as a waterborne agent that had to be ingested to do harm, Chadwick was building an elaborate scheme that would deliver the cholera bacteria directly to the mouths of Londoners. (A modern bioterrorist couldn’t have come up with a more ingenious and far-reaching scheme.) Sure enough, the cholera returned with a vengeance in 1848–1849, the rising death toll neatly following the Sewer Commission’s cheerful data on the growing supply of waste deposited in the river. By the end of the outbreak, nearly 15,000 Londoners would be dead. The first defining act of a modern, centralized public-health authority was to poison an entire urban population. (There is some precedent to Chadwick’s folly, however. During the plague years of 1665–1666, popular lore had it that the disease was being spread by dogs and cats. The Lord Mayor promptly called for a mass extermination of the city’s entire population of pets and strays, which was dutifully carried out by his minions. Of course, the plague turned out to be transmitted via the rats, whose numbers grew exponentially after the sudden, state-sponsored demise of their only predators.)

Why would the authorities go to such lengths to destroy the Thames? All the members of these various commissions were fully aware that the waste being flushed into the river was having disastrous effects on the quality of the water. And they were equally aware that a significant percentage of the population was drinking that water. Even without a waterborne theory of cholera’s origin, it seems like madness to celebrate the ever-increasing tonnage of human excrement being flushed into the water supply. And, indeed, it was a kind of madness, the madness that comes from being under the spell of a Theory. If all smell was disease, if London’s health crisis was entirely attributable to contaminated air, then any effort to rid the houses and streets of miasmatic vapors was worth the cost, even if it meant turning the Thames into a river of sewage.

CHADWICK MAY HAVE BEEN THE MOST INFLUENTIAL MIASmatist of his age, but he had plenty of illustrious company. The other great social crusaders of the age were equally convinced of the connection between foul air and disease. In 1849, the Morning Chroniclesent Henry Mayhew to the heart of the cholera epidemic, in the Bermondsey neighborhood south of the river. The account eventually published deserves its own distinct journalistic genre—olfactory reporting:

On entering the precincts of the pest island, the air has literally the smell of a graveyard, and a feeling of nausea and heaviness comes over any one unaccustomed to imbibe the musty atmosphere. It is not only the nose, but the stomach, that tells how heavily the air is loaded with sulphuretted hydrogen; and as soon as you cross one of the crazy and rotting bridges over the reeking ditch, you know, as surely as if you had chemically tested it, by the black colour of what was once the white-lead paint upon the door-posts and window-sills, that the air is thickly charged with this deadly gas. The heavy bubbles which now and then rise up in the water show you whence at least a portion of the mephitic compound comes, while the open doorless privies that hang over the water side on one of the banks, and the dark streaks of filth down the walls where the drains from each house discharge themselves into the ditch on the opposite side, tell you how the pollution of the ditch is supplied.

The scientific establishment was equally anchored in the miasma theory. In September 1849, the Times ran a series of articles that surveyed the existing theories about cholera: “How is the cholera generated?—how spread? what is its modus operandi on the human frame? These questions are in every mouth,” the paper observed, before taking a decidedly pessimistic stance on the question of whether they would ever be answered:

These problems are, and will probably ever remain, among the inscrutable secrets of nature. They belong to a class of questions radically inaccessible to the human intelligence. What the forces are which generate phenomena we cannot tell. We know as little of the vital force itself as of the poison-forces which have the power to disturb or suppress it.

Despite this bleak forecast, the Times went on to survey the prevailing theories: a “telluric theory that supposes the poison to be an emanation from the earth”; an “electric theory” based on atmopheric conditions; the ozonic theory that attributed outbreaks to a deficiency of ozone in the air; a theory that blamed cholera on “putrescent yeast, emanations of sewers, graveyards, etc.” The paper also mentioned a theory that maintained that the disease was spread by microscopic animalcules or fungi, though it downplayed its viability, claiming that the theory “failed to include all the observed phenomena.”

The diversity of views is striking here—ozone, sewer emanations, electricity—but just as striking is the underlying commonality: all but one of the theories assume that the cholera is somehow being transmitted through the atmosphere. (Snow’s waterborne theory, already a matter of public record, goes completely unmentioned.) The air was the key to the riddle of cholera, and indeed to most known diseases. Nowhere is the philosophy more pronounced than in the writings of the Victorian age’s most beloved and influential medical figure, Florence Nightingale. Consider this passage from the beginning of her groundbreaking 1857 work Notes on Nursing:

The very first canon of nursing, the first and the last thing upon which a nurse’s attention must be fixed, the first essential to a patient, without which all the rest you can do for him is as nothing, with which I had almost said you may leave all the rest alone, is this: TO KEEP THE AIR HE BREATHES AS PURE AS THE EXTERNAL AIR, WITHOUT CHILLING HIM. Yet what is so little attended to? Even where it is thought of at all, the most extraordinary misconceptions reign about it. Even in admitting air into the patient’s room or ward, few people ever think, where that air comes from. It may come from a corridor into which other wards are ventilated, from a hall, always unaired, always full of the fumes of gas, dinner, of various kinds of mustiness; from an underground kitchen, sink, washhouse, water-closet, or even, as I myself have had sorrowful experience, from open sewers loaded with filth; and with this the patient’s room or ward is aired, as it is called—poisoned, it should rather be said.

With Nightingale, the problem is one of emphasis; there’s obviously nothing wrong with ensuring that hospital rooms have fresh air in them. The problem arises when supplying clean air becomes the single most important task for the doctor or nurse, when the air is assumed to be a “poison” that has caused the patient’s illness in the first place. Nightingale believed that cholera, smallpox, measles, and scarlet fever were all miasmatic in nature, and she recommended that schools, homes, and hospitals use a certain “air test,” devised by the chemist Angus Smith, that detected organic materials in the air:

If the tell-tale air test were to exhibit in the morning, both to nurses and patients, and to the superior officer going round, what the atmosphere has been during the night, I question if any greater security could be afforded against a recurrence of the misdemeanor.

And oh, the crowded national school! where so many children’s epidemics have their origin, what a tale its air-test would tell! We should have parents saying, and saying rightly, “I will not send my child to that school, the air-test stands at ‘Horrid.’” And the dormitories of our great boarding schools! Scarlet fever would be no more ascribed to contagion, but to its right cause, the air-test standing at “Foul.”

We should hear no longer of “Mysterious Dispensations,” and of “Plague and Pestilence,” being “in God’s hands,” when, so far as we know, He has put them into our own. The little air-test would both betray the cause of these “mysterious pestilences,” and call upon us to remedy it.

So often what is lacking in many of these explanations and prescriptions is some measure of humility, some sense that the theory being put forward is still unproven. It’s not just that the authorities of the day were wrong about miasma; it’s the tenacious, unquestioning way they went about being wrong. An investigator looking for holes in the theory could find them everywhere, even in the writings of the miasmatists themselves. The canary in the miasma coal mine should have been the sewer-hunters, who spent their waking hours exposed to the most noxious—sometimes even explosive—air imaginable. And yet, bizarrely, the canary seemed to be doing just fine, and Mayhew admits as much in one slightly puzzled passage in London Labour and the London Poor:

It might be supposed that the sewer-hunters (passing much of their time in the midst of the noisome vapours generated by the sewers, the odour of which, escaping upwards from the gratings in the streets, is dreaded and shunned by all as something pestilential) would exhibit in their pallid faces the unmistakable evidence of their unhealthy employment. But this is far from the fact. Strange to say, the sewer-hunters are strong, robust, and healthy men, generally florid in their complexion, while many of them know illness only by name. Some of the elder men, who head the gangs when exploring the sewers, are between 60 and 80 years of age, and have followed the employment during their whole lives.

As Snow observed many times in his writings during the period, there were countless cases of groups sharing the exact same living environment, breathing the exact same air, who seemed to have entirely opposing responses to the allegedly poisonous vapors. If the miasma was truly killing off Londoners, it seemed to choose its victims in an entirely arbitrary fashion. And despite the fact that Chadwick and his commissions had made immense progress in eliminating the city’s population of cesspools, the cholera had nonetheless come roaring back to devastate the city in 1853.

All of which begs the central question: Why was the miasma theory so persuasive? Why did so many brilliant minds cling to it, despite the mounting evidence that suggested it was false? This kind of question leads one to a kind of mirror-image version of intellectual history: not the history of breakthroughs and eureka moments, but instead the history of canards and false leads, the history of being wrong. Whenever smart people cling to an outlandishly incorrect idea despite substantial evidence to the contrary, something interesting is at work. In the case of miasma, that something involves a convergence of multiple forces, all coming together to prop up a theory that should have died out decades before. Some of those forces were ideological in nature, matters of social prejudice and convention. Some revolved around conceptual limitations, failures of imagination and analysis. Some involve the basic wiring of the human brain itself. Each on its own might not have been strong enough to persuade an entire public-health system to empty raw sewage into the Thames. But together they created a kind of perfect storm of error.

MIASMA CERTAINLY HAD THE FORCE OF TRADITION ON ITS side. The word itself is a derivation from the Greek term for pollution; the notion of disease being transmitted by poisoned air dates back to Greek medicine of the third century B.C. Hippocrates was so obsessed with air-quality issues that his medical tracts sometimes sound like instructions for a novice meteorologist. His treatise On Air, Water, and Places begins: “Whoever wishes to investigate medicine properly, should proceed thus: in the first place to consider the seasons of the year, and what effects each of them produces for they are not at all alike, but differ much from themselves in regard to their changes. Then the winds, the hot and the cold, especially such as are common to all countries, and then such as are peculiar to each locality.” (Farr would echo this philosophy centuries later: his Weekly Returns would invariably include a brief weather report, before getting to the body count.) Just about every epidemic disease on record has been, at one point or another, attributed to poisoned miasma. The word “malaria” itself derives from the Italian mal aria, or “bad air.”

Miasma theories were eminently compatible with religious tradition as well. As one might expect from a man of the cloth, Henry Whitehead believed that the Golden Square outbreak was God’s will, but he supplemented his theological explanation with a miasmatic one; he believed that “the atmosphere, all over the world, is at this time favourable to the production of a most formidable plague.” To reconcile this hideous reality with the idea of a beneficent Creator, Whitehead had settled on what might later have been termed an ingeniously Darwinian explanation: that plagues were God’s way of adapting the human body to global changes in the atmosphere, killing off thousands or millions, but in the process creating generations that could thrive in the new environment.

But tradition alone can’t account for the predominance of the miasma theory. The Victorians who clung to it were in almost every other respect true revolutionaries, living in revolutionary times: Chadwick was inventing a whole new model for shaping public health; Farr transforming the use of statistics; Nightingale challenging countless received ideas about the role of women in professional life, as well as the practice of nursing. Dickens, Engels, Mayhew—these were not people naturally inclined to accept the status quo. In fact, they were all, in their separate ways, spoiling for a fight. So it’s not sufficient to blame their adherence to the miasma theory purely on its long pedigree.

The perseverance of miasma theory into the nineteenth century was as much a matter of instinct as it was intellectual tradition. Again and again in the literature of miasma, the argument is inextricably linked to the author’s visceral disgust at the smells of the city. The sense of smell is often described as the most primitive of the senses, provoking powerful feelings of lust or repulsion, triggering mémoires involontaires. (Proust’s original madeleine-inspired reverie was triggered largely by taste, but the power of smell alone is a recurring theme of In Search of Lost Time, and of course smell is an essential component of taste.) Modern brain-imaging technology has revealed the intimate physiological connection between the olfactory system and the brain’s emotional centers. In fact, the seat of many of those emotional centers—the limbic system—was once called the “rhinen-cephalon,” literally “nose-brain” or “smell-brain.” A 2003 study found that strong smells triggered activity in both the amygdala and the ventral insula. The amygdala is an evolutionarily ancient part of the brain, much older than the mammalian higher functions of the neo-cortex; raw instinctual responses to threats and emotionally charged stimuli emanate from the amygdala. The ventral insula appears to play an important role in biological urges, like hunger, thirst, and nausea, as well as in certain phobias. Both regions can be thought of as alarm centers of the brain; in humans, they possess the capacity to override the neocortical systems where language-based reasoning occurs. The brain scans in the 2003 study found that sharply unpleasant smells triggered disproportionately strong responses in both the amygdala and the ventral insula.

In lay terms, the human brain appears to have evolved an alert system whereby a certain class of extreme smells triggers an involuntary disgust response that effectively short-circuits one’s ability to think clearly—and produces a powerful desire to avoid objects associated with the smell. It is easy to imagine the evolutionary pressures that would bring this trait into being. Once again microbes are at the center of the story. Eating meat or vegetation that has already begun the decomposition process poses a significant health risk, as does eating foods that have been contaminated with fecal matter—precisely because of the microbial life-forms that are doing the decomposing. Putrefying foods release several organic compounds into the air; they have names like putrescine and cadaverine. Bacteria recycling energy stored in fecal matter releases hydrogen sulfide into the air. Disgust at the scent of any of these compounds is as close to a universal human trait as we know. You can think of it as a form of evolutionary pattern recognition: over millions of years of evolution, natural selection hit upon the insight that the presence of hydrogen sulfide molecules in the air was a reasonably good predictor that microbial life-forms that could be dangerous if swallowed were nearby. And so the brain evolved a system for setting off an alarm whenever those molecules were detected. Nausea itself was a survival mechanism: it was better to void the contents of your stomach than run the risk that the smell was coming from the antelope you’d just finished eating.

But those telltale molecules—hydrogen sulfide, cadaverine—were clues pointing to a threat. They were not the threat itself. If you press your nose up against a decomposing banana or antelope, you might well make yourself vomit, but you won’t contract a disease from the experience, however repulsive. Breathing in pure methane gas or hydrogen sulfide could kill you, of course, but bacterial decomposition doesn’t release anywhere near enough of these gases to saturate the environment. In other words, methane and putrescine and cadaverine are the smoke. Microbes are the fire.

Basing the alarm system around smell made perfect sense for the environmental conditions of the hunter-gatherer lifestyle. The smell of decay and fecal waste was relatively rare in a world where humans lived in small roving bands; there were no sewers or dustheaps on the savannahs of Africa, precisely because the hunter-gatherers had such low population densities and such mobile lifestyles. You could just leave your waste behind and move on to a new spot; odds were, the bacteria would have recycled it all by the time another human returned. The alarm system of disgust likely evolved both because the threat posed by eating decaying organic matter was a serious one, and because the smell that signaled the presence of decaying matter was unusual. If the smell had been ubiquitous—if, say, some common African flower had begun emitting hydrogen sulfide from its blooms—then the human brain might have evolved another way of anticipating the presence of decaying food.

The trouble is that survival strategies optimized for a hunter-gatherer lifestyle play out differently in a modern city of two million people. Civilization had produced many transformations in the experience of human life: farms, wheels, books, railroads. But civilized life had another distinguishing feature: it was a lot smellier. Densely packed populations of people without modern waste-management systems produced powerfully repellent odors. When Mayhew describes his repulsion at the smell of hydrogen sulfide on the streets of Bermondsey, you can see in the passage a clash between three distinct epochs somehow struggling to share the same space: an industrial-era city with an Elizabethan-era waste-removal system as perceived by a Pleistocene-era brain.

The miasmatists had plenty of science and statistics and anecdotal evidence to demonstrate that the smells of London weren’t killing people. But their gut instincts—or, more like it, their amygdalas—kept telling them otherwise. All of John Snow’s detailed, rigorous analysis of the water companies and the transmission routes of the Horsleydown outbreak couldn’t compete with a single whiff of the air in Bermondsey. The miasmatists were unable to override the alarm system that had evolved so many aeons before. They mistook the smoke for the fire.

MIASMA’S HEGEMONY HAD ONE OTHER BIOLOGICAL BASIS. Our noses are far more adept than our eyes at perceiving the very small. It takes only a few molecules of cadaverine attaching to the olfactory receptors in your upper nasal passages for you to become aware of the smell of decay. But your eyes are useless at the scale of molecules. In many respects, human visual perception is unrivaled among earth’s life-forms—the legacy of a nocturnal mammal who needed to forage and hunt in the dark. But molecules remain several orders of magnitude below the threshold of human visual perception. We can’t see most ordinary cells that those molecules build, even whole populations of cells. A hundred million V. cholerae floating in a glass of water would be invisible to the naked eye. Microscopes had been in use for more than two centuries, and while a few isolated researchers had caught a glimpse of microbes in their labs, the existence of a bacterial microcosmos was still the stuff of fantasy and conjecture for the mid-Victorian mind. But the stench of decomposition was all too real. Smelling was believing.

The miasma theory drew on other sources for its power as well. It was as much a crisis of imagination as it was pure optics. To build a case for waterborne cholera, the mind had to travel across scales of human experience, from the impossibly small—the invisible kingdom of microbes—to the anatomy of the digestive tract, to the routine daily patterns of drinking wells or paying the water-company bills, all the way up to the grand cycles of life and death recorded in the Weekly Returns. If you looked at cholera on any one of those levels, it retreated back into the haze of mystery, where it could be readily rolled back to the miasma theory, given the pedigree and influence of miasma’s supporters. Miasma was so much less complicated. You didn’t need to build a consilient chain of argument to make the case for miasma. You just needed to point to the air and say: Do you smell that?

And of course there were more than a few instances where the statistical evidence did in fact seem to stack the odds in miasma’s favor. Neighborhoods with unsanitary water supplies generally suffered from poor air quality as well; many of them lay at the lower elevations that Farr relentlessly documented in his Weekly Returns. For every sewer-hunter living happily into his sixties, there were a hundred false positives dying in the low elevations of Bermondsey.

Raw social prejudice also played a role. Like the other great scientific embarrassment of the period—phrenology—the miasma theory was regularly invoked to justify all sorts of groundless class and ethnic biases. The air was poisoned, to be sure, but the matter of who fell ill, and what disease they suffered from, was determined by the constitution of each individual breathing in the air. So went Thomas Sydenham’s internal-constitution theory of the epidemic, an eccentric hybrid of weather forecasting and medieval humorology. Certain atmospheric conditions were likely to spawn epidemic disease, but the nature of the diseases that emerged depended partly on a kind of preexisting condition, a constitutional susceptibility to smallpox, or influenza, or cholera. The distinction was often defined as one between exciting and predisposing causes. The exciting cause was the atmospheric condition that encouraged a certain kind of disease: a specific weather pattern that might lead to yellow fever, or cholera. The predisposing cause lay in the bodies of the sufferers themselves. That constitutional failing was invariably linked to moral or social failing: poverty, alcohol abuse, unsanitary living. One alleged expert argued in 1850: “The probability of an outburst or increase during [calm, mild] weather, I believed to be heightened on holidays, Saturdays, Sundays, and any other occasions where opportunities were afforded the lower classes for dissipation and debauchery.”

The idea of one’s internal constitution shaping the manifestation of disease was not just useful for affirming social prejudices about the moral depravity of the lower classes. It also helped paper over a massive hole in the theory itself. If the miasma seemed unusually capricious in its choice of victims for poison allegedly circulating in the atmosphere—if it killed off two housemates but left the remaining two unscathed despite the fact that they were all breathing the same air—the miasmatists could simply point to the differences in constitution between the victims and the survivors to explain the disparity. Although the poisonous vapors were distributed equally through the environment, each inner constitution possessed its own distinct vulnerability.

Like much of the reasoning that lay behind the miasma theory, the idea of an inner constitution was not entirely wrong; immune systems do vary from person to person, and some people may indeed be resistant to epidemic diseases like cholera or smallpox or plague. The scaffolding that kept miasma propped up for so long was largely made up of comparable half-truths, correlations mistaken for causes. Methane and hydrogen sulfide were in fact poisons, after all; they just weren’t concentrated enough in the city air to cause real damage. People were more likely to die of cholera at lower elevations, but not for the reasons Farr imagined. And the poor did have higher rates of contagion than the well-to-do, but not because they were morally debauched.

Yet miasma had just as much to offer the liberals as it did the conservatives. Chadwick and Nightingale and Dickens were hardly bigots where the working classes were concerned. Miasma, for them, was not a public sign of the underclasses’ moral failing; it was a sign of the deplorable conditions in which the underclasses had been forced to live. It seemed only logical that subjecting such an immense number of people to such deplorable living environments would have a detrimental effect on their health, and of course, the liberal miasmatists were entirely right in those basic assumptions. Where they went wrong was in assuming that the primary culprit lay in the air.

And so, on August 29, when the Morning Chronicle welcomed Benjamin Hall to his new job as president of the Board of Health, the editors included more than a few cutting remarks at the expense of Edwin Chadwick; yet they embraced the theory of miasma with both arms and urged the new president to continue the work of enforcing the Nuisances Removal and Contagious Diseases Prevention Act. There may be no clearer example of miasma’s dark irony: on the very day that the outbreak in Golden Square was beginning, one of London’s most prestigious papers was urging the Board of Health to accelerate its work poisoning the water supply.

MIASMA TURNS OUT TO BE A CLASSIC CASE OF WHAT FREUD, in another context, called “overdetermination.” It was theory that drew its persuasive power not from any single fact but rather from its location at the intersection of so many separate but compatible elements, like a network of isolated streams that suddenly converges to form a river. The weight of tradition, the evolutionary history of disgust, technological limitations in microscopy, social prejudice—all these factors colluded to make it almost impossible for the Victorians to see miasma for the red herring that it was, however much they prided themselves on their Gradgrindian rationality. Every research paradigm, valuable or not, in the history of ideas has been buttressed by a comparable mix of forces, and in this sense the deconstructionists and the cultural relativists—so often the subject of mockery lately—have it right to a certain extent, though they tend to place undue stress on purely ideological forces. (Miasma was as much a creature of biology as of politics.) The river of intellectual progress is not defined purely by the steady flow of good ideas begetting better ones; it follows the topography that has been carved out for it by external factors. Sometimes that topography throws up so many barricades that the river backs up for a while. Such was the case with miasma in the mid–nineteenth century.

But most of these dams eventually burst. Yes, the path of science works within regimes of agreement and convention, and history is littered with past regimes that were overthrown. But some regimes are better than others, and the general tendency in science is for explanatory models to be overthrown in the name of better models. Oftentimes because their success sows the seeds of their destruction. Miasma became so powerful that it inspired a massive, state-sponsored intervention in the daily lives of millions of people, clearing the air by draining the cesspools. That intervention, miscalculated as it was, had the paradoxical effect of making the patterns of the epidemic more visible, at least to eyes that were capable of seeing them. And seeing the patterns more clearly means progress, in the long run at least.

JOHN SNOW SPENT MOST OF TUESDAY SEARCHING FOR patterns. In the morning he was knocking on doors, interrogating strangers in the street, asking anyone he encountered for anecdotal evidence about the outbreak and its victims. The clues he found were tantalizing, but too many doors went unanswered, and the dead couldn’t report on their recent drinking habits. Personal testimony would not take him far in an evacuation zone. And so at midday he paid a visit to the Registrar-General’s Office, where Farr gave him an early look at the numbers being calculated for the week. Eighty-three deaths had been reported in Soho between Thursday and Saturday. Snow asked for a complete list, including addresses, and returned to Broad Street to continue his sleuthing. He stood at the base of the pump, and ran through the addresses on the list. From time to time, he gazed out at the empty streets around him, imagining the paths the residents might take to find their way to water.

It was going to take more than body counts to prove that the pump was the culprit behind the Broad Street epidemic. Snow was going to need footprints, too.

ACE BOOKS, NEW YORK

“BLUE STAGE OF THE SPASMODIC CHOLERA”

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