[William] Farr had been hired to track the most elemental of demographic trends: the number of births, deaths, and marriages in England and Wales. Over time, though, he had refined the statistics to track more subtle patterns in the population. “Bills of Mortality” dated back to the plague years of the 1600s, when clerks first began recording the names and parishes of the dead. But Farr recognized that these surveys could be far more valuable to science if they included additional variables. He waged a long campaign to persuade physicians and surgeons to report a cause of death wherever possible, drawing upon a list of twenty-seven fatal diseases. By the mid-1840s, his reports tallied deaths not only by disease, but also by parish, age, and occupation. For the first time, doctors and scientists and health authorities had a reliable vantage point from which to survey the broad patterns of disease in British society. [John Snow is investigating the possibility that the cause of a cholera outbreak in London is in the water, not as the most popular theory of the day claims bad air, a.k.a. miasma.] Without Farr's Weekly Returns, Snow would have been stuck in the street-level view of anecdote, hearsay, and direct observation. He might still have been able to build a theory of cholera on his own, but it would have been almost impossible to persuade anyone else of its validity.
Farr was a man of science, and shared Snow's belief in the power of statistics to shed light on medical riddles. But he also shared many assumptions with the miasma camp, and he used the number-crunching of the Weekly Returns to reinforce those beliefs, Farr thought that the single most reliable predictor of environmental contamination was elevation: the population living in the putrid fog that hung along the riverbanks were more likely to be seized by the cholera than those living in the rarefied air of, say, Hampstead. And so, after the 1849 outbreak, Farr began tabulating cholera deaths by elevation, and indeed the numbers seemed to show that higher ground was safer ground. This would prove to be a classic case of correlation being mistaken for causation: the communities at the higher elevations tended to be less densely settled than the crowded streets around the Thames, and their distance from the river made them less likely to drink its contaminated water. Higher elevations were safer, but not because they were free of miasma. They were safer because they tended to have cleaner water.
Farr was not entirely opposed to Snow's theory. He seems to have entertained the idea that the cholera was somehow originating in the murky waters of the Thames, and then rising into the smoggy air above the river as some kind of poisonous vapor. He had clearly followed Snow's publications and presentations closely over the years, and engaged the theory on occasion in the editorials that would sometimes accompany the Weekly Returns. But he remained unconvinced by the purely waterborne theory. He also suspected that Snow would have a difficult time proving his theory. "To measure the effects of good or bad water supply," Farr editorialized in November of 1853, “it is requisite to find two classes of inhabitants living at the same level, moving in equal space, enjoying an equal share of the means of subsistence, engaged in the same pursuits, but differing in this respect,—that one drinks water from Battersea, the other from Kew.... But of such experimenta crucis the circumstances of London do not admit.”
Snow must have taken that last line as a slap in the face, having heard the exact same Latinate phrase used against him after the publication of his original cholera monograph four years before. Yet despite his skepticism, Farr had been intrigued enough by Snow's waterborne theory to add a new category to his Weekly Returns. In addition to tracking the age and sex and elevation of the cholera victims, Farr would now track one additional variable: where they got their water. [pp. 101-102]
Miasma’s hegemony had one other biological basis [the first was the olfactory alarm system of disgust that is triggered by our detection of certain molecules, like hydrogen sulfide or cadaverine]. 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 [a poor person who roved about in the sewers for any items or substances of value that could be sold] 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. …
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. [Thomas Gradgrind is the notorious school board Superintendent in Dickens's 1854 novel Hard Times who is dedicated to the pursuit of profitable enterprise. His name is used generically to refer to someone who is hard and only concerned with cold facts and numbers. Wikipedia] 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. [pp. 131-135]
