John Snow was a mere teenager the first time he watched a patient’s flesh turn pale and cold from the tourniquet’s grip. Almost twenty years later, the lingering images still haunted his memory. Above all, he remembered patients in pain. He could still hear their screams as the razor-sharp blade sliced deep into the limb, shredding the protective haze of morphine. Each cut nerve brought a new wave of agony, but, as the incision revealed the bone, a new kind of anguish began. As his mentor, William Hardcastle, cut into the clusters of densely packed nerve endings that surrounded the bone, they translated the intrusion into a thousand rivers of anguish that overwhelmed the patient’s very soul. The lingering passage through the dense mineral matrix seemed more like torture than surgery. Faces crushed by pain still howled across the years for relief, but that relief never began before the thud of the limb in the catch basket.
Surgical pain was Snow’s grim tutor throughout his medical training. Since coming to London, he had spent endless hours in the operating rooms of Westminster Hospital. After finishing medical school, he had served as one of the hospital’s house surgeons (the equivalent of today’s surgery resident). He had participated in hundreds of surgical procedures and each one was a race against pain. A good surgeon was a fast surgeon. Every surgeon in Napoleon’s army had to prove he could amputate a leg in less than three minutes. Until the winter of 1846, speed was the patient’s only friend.
That year, on the morning of December 28, John Snow and two colleagues walked through the bitter cold that had gripped the city since Christmas Eve. The implications of what they had just seen consumed his thoughts. The fate of a rotten tooth had just revealed to them the future of surgery.
The tooth belonged to a female patient of Dr. James Robinson, a friend of John Snow. On that late December morning, Snow and his companions had observed as Robinson picked up his pliers, grasped the tooth, rocked it back and forth, and pulled. The astonished audience watched and listened in awe as the bloody tooth emerged. Their amazement arose not from what they saw or heard, but from what they did not. The patient had not cried out, moaned, or even flinched. Robinson’s patient had no special resistance to pain. The incredible quiet had come from a bottle of ether.
Just nine days earlier, Robinson had given the first demonstration of ether in England. Until that moment, pain and the struggle to control it had pervaded the practice of the British surgeon. By the time Snow saw Robinson in action, he had performed half a dozen procedures and was, by default, the country’s leading expert on the use of ether, a technique he had imported from America just weeks after the publication of the first paper describing its use appeared in Boston. On that late December morning, the three men stayed to question Robinson, drawing from his relatively shallow well of experience as the patient recovered.
They emerged from Robinson’s office into the oppressive air of winter. Tens of thousands of stoves and furnaces that had burned through the cold heart of the British night filled the air with smoke. The coal-fired engines of London’s factories added thick black clouds to the pall of soot that sank steadily downward on the populace. At the same time, another cloud was rising from the streets themselves. The steady hammering of hundreds of thousands of horseshoes was grinding the cobblestones into a fine powder. The result was a gritty mixture of stone dust and burned coal that accumulated in every corner of the lives and lungs of the city’s inhabitants.
After ten years Snow had learned to live with London’s abuses. As the three men parted company and Snow walked toward his home in Soho, he gave little thought to the city’s cold, gritty air. On that morning in December, his mind was fixed on the miracle of silent surgery.
Snow knew that ether would change everything. He also recognized the danger inherent in ether’s magic. Physicians would need to walk a fine line between the reemergence of pain because of too little ether and the disaster of an overdose.
The power of ether had impressed him, but Robinson’s technique had been crude and his methods imprecise. The dentist had simply allowed the patient to inhale ether from a flask until she faded from consciousness. Snow’s knowledge of chemistry told him that the evaporating ether cooled the inhaler. As it cooled, the amount of ether vapor rising from the flask and entering the patient’s lungs decreased. This meant that Robinson had no way to know precisely how much ether he was giving the patient. Furthermore he had no real way to control the amount she inhaled during the operation. At a time when no one else in London seemed to see these problems, Snow had already begun to imagine how to solve them.
In the years since he arrived in London, Snow had turned his apartment into a buzzing laboratory, an outlet for his inquisitive mind. Even as a medical student, he had pieced together enough equipment to perform a study demonstrating that the arsenic used to preserve cadavers was rising from the dissecting table and sickening his fellow medical students.
At the time Londoners often used candles made from palm oil. Manufacturers added arsenic to help them burn brighter and more evenly. Snow’s attempt to study arsenic levels released by burning candles almost ended his research career. He and a fellow medical student were hunched over their experiment, when an apparatus he had designed to collect the fumes from the candle burst into flames. Fortunately the two were quick enough to extinguish the blaze before it consumed Snow’s nascent laboratory.
In the years since, his experimental technique had improved and his laboratory had grown to a point where he was ideally prepared to investigate the use of ether. He had the instruments needed to measure the temperature and pressure of gases with a high degree of precision. He had the cages and tanks he needed to test ether on a broad range of animals and, during the month that followed, he filled them with finches, thrushes, frogs, mice, rats, and even fish. He knew and had worked with high-precision machinists capable of turning his designs for medical devices into working prototypes.
So for the next month, he brought all his skills, experience, and laboratory resources to bear as he focused on the single goal of understanding and refining the administration of ether. He devoted all his free time to the task and before two weeks were over he had the data necessary to predict the dose of ether over a broad range of conditions. Before the end of January, he had administered ether in precise doses to the menagerie of small animals in his lab and recorded their response in fine detail. At the same time, he had designed and assembled an ether inhaler intended to maintain a constant temperature and deliver a stable dose throughout a surgical procedure.
So by early February Snow had developed a detailed understanding of the effects of the drug, generated data essential for its controlled administration, and invented an inhaler far superior to any other. He arranged to present his findings at the regular evening meeting of the Westminster Medical Society.
It is no exaggeration to say that the society was the closest thing John Snow had to a family during his time in London. For much of his time there, he had no relatives in the city. There is no record of any romantic relationship during those years. His life was medicine. His friends were members of the society and he rarely missed their weekly meetings. From his first paper on the resuscitation of newborn infants to his last, he tested every new idea on his medical family.
Snow had presented his research to the meetings of the society before, but never with such overwhelming authority. Less than two months after first learning of ether’s power, he had established himself as an expert in its use. His presentation impressed his colleagues and their acclaim came as a great triumph to the young doctor.
Snow however does not appear to have been motivated by any need for praise or money. He made no effort to patent his inventions. Instead he published detailed descriptions to allow others to copy them for their own use. Initially he did not even have notions of establishing a practice in the administration of ether. That changed on a January morning in 1847 as Snow was leaving the hospital.
Years later, a friend recounted the story:
[H]e met a druggist whom he knew bustling along with a large ether apparatus under his arm. “Good morning!” said Dr. Snow. “Good morning to you, doctor!” said the friend; “but don’t detain me, I am giving ether here and there and everywhere, and am getting quite into an ether practice. Good morning, doctor!” Rather peculiar! said the doctor to himself; rather peculiar, certainly! for this man has not the remotest physiological idea. An “ether practice! If he can get an ether practice, perchance some scraps of the same thing might fall to a scientific unfortunate.
At the time, Snow was, indeed, a “scientific unfortunate.” He had tried to establish a clinical practice for more than eight years and was still struggling to make ends meet. He had contracts with several sick clubs, a system akin to a crude HMO in which doctors received a fixed fee and in return provided whatever care was required by members of the clubs. He also worked at the dispensary of Charing Cross hospital. In both cases, he was providing care to the working poor with minimal compensation.
To some extent, the cause of his financial struggle lay in the peculiar nature of the man. John Snow was an acquired taste. His voice, which a friend described as “painful” on first hearing, left a poor first impression. He also had the annoying habit of telling patients the truth rather than what they wanted to hear. In Newcastle his inclination to tell patients that Victorian medicine had little to offer them had resulted in bitter arguments with William Hardcastle and may have contributed to his decision to leave the city for further training. In London it left patients dissatisfied and cut into Snow’s ability to generate an income. Last, but not least, he lacked the breeding, elite credentials, and connections necessary to attract the members of London’s upper crust.
To make his financial matters worse, he had poured all that he could save of his meager income into research. That chance encounter with a druggist began a merger of Snow’s research and his clinical work that would redefine his professional life. On January 28, exactly one month after observing Richardson’s tooth extraction, John Snow put his first patient to sleep.
Over the next year, John Snow administered ether more than a hundred times for everything from mastectomies to dental procedures. His anesthesia practice opened a door to wealthier patients and brought a new source of income that allowed him to substantially increase his research activity. At a time before the specialty even had a name, he was on his way to becoming one of the most respected anesthesiologists in England.
But as his career developed, cholera was making its way across Europe to find him again.
After 1832 cholera had retreated to India where it festered until the hot summer of 1845 when it marched on Kabul. By 1846 it had reached into the Middle East, killing twelve thousand people in Teheran and thirty thousand in Baghdad. On a single, horrible night in 1847, almost three thousand pilgrims died at Mecca. In 1848 it made its way to a district on the banks of the Thames known as Horsleydown.
Named after a pasture used to graze horses in the sixteenth century, Horsleydown no longer appears on maps of London. Tower Bridge bisected the riverfront neighborhood when it was built in the late nineteenth century, relegating Horsleydown to the history books. In the 1840s however it was very much alive. An exotic blend of immigrants had settled there and established the breweries, tanneries, and warehouses that dotted the area. Above all else, its proximity to the docks made it the rough-and-tumble home to the seamen and dockworkers who serviced the endless stream of merchant ships that flowed into the city from all over Europe.
Two events have kept Horsleydown from disappearing entirely into the mists of history. The most dramatic was a fire that started in a jute warehouse on Tooley Street in 1861, near the wharf. A neighboring building containing resin, oil, and tallow exploded in flames and spewed its burning contents across the neighborhood. The resulting fire raged through the district for weeks, consuming the low wooden buildings in a blaze that could be seen for fifty miles.
The buildings that burned had provided the setting for a less dramatic, but ultimately more significant moment thirteen years earlier in September 1848. A seaman by the name of John Harnold had just returned from the port of Hamburg aboard the merchant ship Elbe. With cholera raging in the German port city, British troops placed the ship in quarantine.
Harnold was feeling a bit out of sorts and wanted nothing more than to lie down in a proper bed and rest. He could not tolerate the foul, cramped confines of a merchant ship when the city and freedom were so close at hand. In the busy, buzzing confusion of the docks, slipping ashore was far easier than the masters of quarantine liked to pretend.
So he made land and walked through Horsleydown to a rented room on Gainsford Street, just two blocks from the docks. He lay down to rest, carrying the seeds of the epidemic in his belly.
When cholera struck at John Harnold, it did so with such force that the sturdy seaman died in just two hours. Within days the nightmare had begun to replay itself throughout the district. The second great epidemic of cholera had begun.
The disease that was once a stranger to London’s physicians had taken on a terrifying familiarity. The first epidemic, which began in Sunderland in 1831, had killed 8,500 Londoners before ending in 1833. When Mr. Russell, an apothecary, came to see the stricken man, he knew in a moment what had happened. Dr. Parkes from the Board of Health confirmed that Asiatic cholera had arrived. The news raged through the city’s medical community and quickly reached the busy anesthesiologist John Snow.
Fourteen years had passed since the young John Snow watched cholera slaughter the miners of Killingworth. In those years the puzzle of its cause had never lost its hold on him. During his years in medical school, first in Newcastle and then at the Hunterian School of Medicine on Great Windmill Street in Soho, he had learned the prevailing medical beliefs about cholera. Those theories however did not seem to fit the disease that he had come to know with a chilling intimacy.
The medical orthodoxy held that diseases were either epidemic or contagious. The epidemic diseases that had ravaged Europe since the birth of nations included the black plague, typhus, yellow fever, and malaria. Although contagious diseases had the potential to pass from person to person, according to these theories, epidemic diseases did not. Among the most terrifying features of these epidemics was their apparent ability to attack people who had no exposure to the disease. Contagious diseases moved slowly from one person to the next and could be contained by isolation. Epidemic diseases, on the other hand, could move with explosive speed. Quarantine could not contain them.
The dominant explanation for the cause of these epidemics held that they spread by a poison in the air, a miasma. Only an agent spread by the wind could move with such speed and defeat all efforts to stop it. Gaps in scientific knowledge with respect to the composition of the atmosphere allowed one to imagine the existence of an airborne poison. Malaria even took its name, which translates as “bad air,” from this misconception. More than half a century would pass before scientists understood that the plague, typhus, and malaria rode in on rats, fleas, and mosquitoes, not bad air.
Cholera, with its demonstrated ability to devastate a wide area in short order, not to mention its apparent ability to slip through the most stringent quarantine, was, by definition, an epidemic disease. Classic medical wisdom held that, as an epidemic disease, cholera could not spread through contagion. In fact in the 1830s the Lancet, England’s leading medical journal, published a series of articles that derided the foolish notion that cholera was contagious.
John Snow had a problem with this line of thinking. As a young man in Killingworth, he had watched cholera spread from miner to miner and then on to family members. He found nothing compelling in the arguments against contagion. However he had also seen the explosion of disease in Gateshead that occurred suddenly and simultaneously over a wide area. Cholera it seemed was both contagious and epidemic.
Cholera roamed the streets of London through the fall of 1848, killing at will. During those months, Snow’s probing led him to a crack deep in the foundation of current medical thinking. As he burrowed deeper into that crack, the tired concrete of ancient beliefs began to crumble around him.
If an airborne poison spread cholera, then that toxin should behave in a manner similar to the toxic anesthetic agents that Snow had been testing with such rigor in his home laboratory. Every gas he had ever tested showed a consistent, predictable dose-response relationship. Every person or animal exposed to a given dose of anesthetic had roughly the same response. But cholera selected its victims from among families living in the same buildings with no apparent regard for the fact that they all breathed the same air. Even when cholera did strike, its severity varied. Half its victims managed to survive the attack, while some died in a matter of hours. Cholera’s cause, whatever it was, acted unlike any gas he had ever seen.
Advocates of airborne causes also pointed to the pathology of the disease to justify their case. Cholera’s victims, blue and breathless, appeared to have been asphyxiated. To many this seemed to provide clear evidence that cholera struck at the lungs. Snow looked not at how cholera ended, but how it began. In every case the disease attacked the gut first. What if cholera’s agent was not inhaled, but ingested?
Here however Snow’s thinking hit a wall. Cholera’s choice of targets seemed to have even less to do with the food and drink its victims consumed than with the air they breathed. Some shunned mutton and others avoided vegetables. Some drank only brandy and others drank well water. If an ingested poison caused the disease, that poison had no consistent hiding place.
Then, as the epidemic stretched toward the winter, John Snow happened on a radical solution. What if a tiny organism, one too small to be seen with the naked eye, caused the disease? Such an organism could hide in any manner of food or drink. More importantly, if an invisible bit of stool found its way into the mouth of a family member or visitor, the process could begin again and the outbreak could continue.
In a world of stinking privies and foul cesspools, a world where the streets were crusted with manure, rotting garbage, and human excrement, a world filled with things vile, dangerous, and obvious, Snow’s notion that something undetectable could wreak such carnage was among his most radical.
Snow was steeped in the science of his day and knew well that advances in microscopy had revealed an unseen world of strange creatures. However people seemed able to consume these mysterious “animalcules” with no effect. The medical establishment paid little attention to these insignificant, odorless curiosities. How could something so small have any consequence for humans?
Snow followed a radical line of thought to counter this objection. He proposed that most of these animalcules were indeed harmless, but some specific types of organisms or at least one type was far from benign. If that specific organism were capable of replicating in the human gut, then perhaps, when its numbers were large enough, it could cause the explosive diarrhea that characterized cholera.
But Snow’s carefully constructed explanation had a hole. Ingestion seemed to require close contact with a previous victim. This theory left unexplained the explosive outbreaks that struck suddenly over broad areas. Then, in the fall of 1848, John Snow had an idea.
Few people in London paid as much attention to drinking water as did John Snow. That relationship began with a book. As an apprentice in Newcastle, he came across a copy of Return to Nature or A Defence of the Vegetable Regimen by John Frank Newton. This strange, rambling screed warns of “the dire effects on the human frame of animal food,” drawing on everything from the writings of Cicero to the science of Justus von Liebig to justify a vegetarian diet. As a teenage apprentice, Snow must have found something compelling in the book, for he spent much of the remainder of his life as a vegetarian. This was not a casual undertaking in the unrefrigerated world of Victorian England. The long and literally fruitless winters were bland at best and threatened malnutrition at worst. Still Snow persisted at a time when this peculiar habit made him an object of curiosity.
Snow rarely did anything halfway and so he took on the book’s other essential dietary advice. Not only was he an ardent and active teetotaler but from the time he first assembled a still in his quarters in Newcastle until the day he died, he drank distilled water. Newton’s book asserted that even ordinary drinking water would undermine the benefits of a vegetarian regimen, primarily because of what he believed to be the routine presence of “animal oils” in drinking water. To Snow’s early mentors, this was the strange and annoying habit of a confused adolescent, but Snow never relented. When he arrived in London, one of his first acts was to set up a still for his drinking water.
Snow’s use of purified water may have saved his life as he found himself again and again at the epicenter of the cholera epidemic in England. It also offered a rare perspective on the water consumption of his countrymen. Perhaps it was during one of his distillation runs that the idea occurred to him. What if a drinking water supply were contaminated with fecal matter from a cholera victim? The deadly water could spread through a network of pipes and reach the water pitchers of unsuspecting victims over a broad area in a single moment.
His long string of cognitive leaps had landed on a solution. He did not have to decide if cholera was a contagious or an epidemic disease. It could be both. The dichotomy was a false one and now he had the mechanism to explain it.
John Snow’s indictment of London’s drinking water was not radical in and of itself. The medical community recognized that dirty water could make you sick. Snow, however, parted ways with his colleagues when it came to how water could make you sick. They held that fermenting organic matter in drinking water could release the same foul-smelling miasmatic poisons that caused epidemics and that these poisons could kill. Certainly, they conceded, drinking straight from the reeking water of the Thames could cause disease and might even spread cholera. Snow’s theory required no such miasma. If his ideas were correct, water with no smell or visible contamination could kill.
John Snow had enough experience in the arena of ideas to know that a theory resting on so many untested suppositions would not carry much weight among his medical peers. He needed data. In the study of anesthesia, he had been able to conduct experiments to test his hypotheses. In his investigations of the cause of cholera, his superb skills in the laboratory could not give him the data he needed.
Animal experiments were not an option. Efforts to find the cause of cholera during the first epidemic had included feeding the excretions of cholera victims to a variety of animals. None of them had developed cholera. This was taken as proof that the cause of cholera was not ingested. Snow did not believe this, but had to find a way to disprove it.
Conducting human experiments was ethically impossible. To do so would have involved assembling two similar groups of people and exposing one group to contaminated water and one to pure water. If his theory was right, many of the subjects would have died in his quest for the truth. Snow could not conduct the trial, but he did have an alternative. He could wait for cholera to conduct the trial for him.
So Snow had to watch and wait. Cholera’s experiment required a neighborhood with two water supplies. If it contaminated one and not the other, the resulting outbreak would point an accusatory finger at the contaminated drinking water. For Snow to begin to prove his theory, cholera needed to conduct the experiment. Unfortunately the deadly disease was not in the habit of publishing the results of its grim research. Instead, amidst the chaos of the epidemic, Snow would need to find the data.
Month after month, John Snow sat on his revolutionary idea. He broke his silence only once, when he tested the theory on two trusted colleagues. They listened with interest, but remained unconvinced by Snow’s argument. Their skepticism did not discourage Snow, but it did convince him to wait until he could gather more data before presenting his theory to a wider audience.
For almost a year Snow’s notion stayed within this small circle. During that year he developed a network of informants to help him track the disease’s every move. As it struck one neighborhood after another, he visited the site of each cluster, talking to the doctors involved and to the survivors. Through the winter and spring, his investigations came up empty. Then in the summer of 1849 cholera showed its hand.
Cobbled together from pieces of London’s history, the systems that carried water and waste had emerged from the city’s agrarian past, evolving according to the expediency of the moment. There was no master plan and the architects of disaster rushed in to fill the void.
London’s first residents had relied on the Thames and its tributaries for their water. As the city grew, many residents of London and the farms around it dug wells to find drinking water. Others built cisterns to capture rainwater. With further growth, water companies began to supply piped water, much of it drawn from the Thames. With the help of their friends in Parliament, the water companies carved up the city into districts over which they maintained exclusive control. By 1849 a Londoner might rely on wells, cisterns, piped water, or even buckets of river water. The choice depended on location, income, and personal preference. That choice would come to mean the difference between living and dying.
London’s system for disposing of wastewater depended on the separation of waste. Feces and urine accumulated in the privies, which were placed at some distance from any residence. No amount of perfume or lime could make a trip to one of these Victorian outhouses palatable. One routinely emerged gasping for breath and praying for constipation. A nighttime trip was to be avoided at all costs, so a portion of the city’s urine was stored under its beds in chamber pots during the night and flung out the window in the morning accompanied by a cry of “Gardez loo!,” a bastardazation of the French “Gardez l’eau,” or “watch out for the water.” Wastewater from bathing, laundry, dishwashing, and household cleaning accumulated in the cesspools where water would seep into the ground and solids would slowly accumulate.
The guild of night soil rakers not only cleaned the privies or ash pits (euphemistically called because of the practice of spreading fireplace ash on them in an attempt to control odor), but also paid for the privilege as they could resell the valuable fertilizer to farmers on the outskirts of the city. Periodically they also cleaned the waste that accumulated in the bottom of London’s cesspools. The rakers could never come often enough.
Sewers were intended to drain the streets. As the streets were far from clean, the sewers carried far more than rainwater. Grant’s report on the outbreak at Albion Terrace concluded that the source of the problem was simply the miasma escaping from the rotting organic matter in the sewers.
The Vibrio cholerae bacterium is a creature that thrives in the warmth and moisture of a human intestine. Once out in the world, it struggles to survive long enough to find another victim. The warm waters of India suited the microscopic killer, helping it to find refuge between pandemics. For most of the year, the cold water of southern England was far less hospitable. Then as the summer sun warmed the Thames, London came to look, from the perspective of cholera, more and more like Calcutta.
The Surrey buildings, a cluster of small apartments in the dockside district of Horsleydown, drew their water from a well. During heavy rains, the well had a tendency to overflow. When it did the water would wash up onto the street before draining back down into the well. Whatever illness this caused before the summer of 1849 had drawn no notice. In late July of that year however, cholera was so widespread in this poor district on the Thames that two of the buildings’ residents had the disease. Their family members had dumped the wash water from the sheets into the gutter. As the rain fell, it scoured the gutters and Vibrio cholerae poured into the well.
Eleven people in the Surrey buildings would die from cholera over the two weeks that followed. When Snow investigated and learned of the contamination of the well, he saw it as evidence of waterborne disease. But the residents of the Surrey building were poor; they were expected to die of cholera. The disease was easily found in the surrounding neighborhoods. Even though the rate of disease was far higher in the Surrey buildings, Snow suspected this evidence alone would not prove compelling.
At almost the same time however, cholera had infiltrated Albion Terrace, a far different neighborhood about a mile upstream and far removed from the squalor of the river’s edge. When John Snow learned that cholera had killed twenty people from a row of seventeen upper-class homes in a matter of days, he rushed to the neighborhood to investigate. Albion Terrace was an island of devastation surrounded by a cholera-free sea.
During the ten days of the Albion Terrace outbreak, 1,231 people had died of cholera in London, but this outbreak among the affluent had already attracted the attention of the General Board of Health. When Snow arrived, their emissary, an engineer by the name of Thomas Grant, had already begun his investigation.
The residents had learned to live with flooded basements after each heavy rain. Mr. Grant’s excavations had revealed how cesspools, swollen with rainwater, had overflowed and contaminated the row of interconnected cisterns that served the buildings. He pointed the finger of blame at the resulting stench together with the emanations from an open sewer some four hundred feet away. A miasma, Grant concluded, had caused the disaster.
When John Snow examined samples that Grant had provided him from two of the cisterns, he reached a far different conclusion. Even before he reached his laboratory, Snow sensed that he had the evidence he needed. As he picked through the foul sludge that Grant had scooped from a thick layer on the bottom of the tanks, he found the peel of a grape.
Something more than mere wash water had found its way into the drinking water. Unless someone in the building was in the habit of peeling grapes, the empty peel that Snow found had first passed through a human digestive tract. This meant that a bit of privy soil had found its way into the cistern and with it the seeds of cholera.
Snow rushed to put his theory to paper. Night after long night, he assembled his case. As he wrote, the undigested bits of food in the specimens from Albion Terrace that sat in his office fermented with such ferocity that the corks would pop out of their bottles on the shelves above him.
Less than a month after the outbreak, he walked into the office of John Churchill and Sons with a manuscript under his arm. By early September the Soho publisher had provided Snow with a stack of the thirty-one page monograph still smelling of fresh ink. Having conducted the research and paid for its publication, he set to work distributing copies of On the Mode of Communication of Cholera to colleagues and medical journals.
If Snow had hoped for a quick acceptance of his theory, the response to his monograph was disappointing. Even though the notion that cholera was contagious had grown far more acceptable since 1831, London’s two leading medical journals seemed unimpressed by Snow’s efforts. The review in the Lancet was only two paragraphs long, one of which was simply a quote from the monograph. In this cursory treatment, the editors asserted that Snow’s arguments against an airborne cause were “not by any means decisive.” Recognizing that the review was too short to fully present and rebut Snow’s work, they suggested that their readers refer to the essay, but cautioned that it “must of course be received with great limitation.”
The London Medical Gazette, London’s other leading medical publication, published a far more extensive, but no less dismissive, review. The review discarded Snow’s analysis of the Albion Terrace outbreak, stating:
There is, in our view, an entire failure of proof that the occurrence of any one case could be clearly and unambiguously assigned to the use of the water…. Foul effluvia from the state of the drains [i.e., an airborne miasma from the sewers] afford a more satisfactory explanation of the diffusion of the disease.
It went on to close with a wisp of faint praise:
Notwithstanding our opinion that Dr. Snow has failed in proving that cholera is communicated in the mode in which he supposes it to be, he deserves the thanks of the profession for endeavouring to solve the mystery.
Snow pored over the reviews, looking not for affirmation, but for a hint as to what it would take to convince his audience. The London Medical Gazette spelled it out:
The experimentum crucis would be, that the local water conveyed to a distant locality, where cholera had been hitherto unknown, produced the disease in all who used it, while those who did not use it escaped.
Even as he shot back at the London Medical Gazette with a letter correcting the errors in their review, John Snow had begun to search for a place where cholera and chance had performed an experimentum crucis.
Snow pored over any and every publication that described the impact of cholera on communities throughout the kingdom. He read through the voluminous reports of the registrar general that tabulated the deaths from cholera throughout the epidemic, searching for areas where cholera had either taken an extreme toll or hardly visited. In each case he paid particular attention to the water supply, searching for cholera’s path. Where the reports lacked detail, he sent letters to local physicians seeking their help.
Example after example poured into Snow’s small apartment on Firth Street in Soho. One report came from his hometown of York where a terrible outbreak had struck the narrow lanes along the River Ouse where he had spent his childhood. He could still remember watching neighbors draw their water from the river. The deaths from cholera in York, he learned, came to an abrupt halt when local health officials brought in water from far upstream and began anew when the importation of water stopped.
Snow made note of other towns where a change in water supply had accompanied a change in the death toll. Exeter, which had seen 345 cholera deaths in 1832 during the first epidemic, saw only 20 in 1849. Between the two outbreaks the town, which had been using a polluted millstream, built a new waterworks in cleaner waters far upstream. Hull, on the other hand, had seen a sixfold increase in cases after moving the water supply from small streams in the hills to the river flowing through the center of town.
As new reports came in, Snow assembled them into a paper that would give far more evidence to support his theory. Less than a month after the Lancet and the London Medical Gazette had printed dismissive reviews of his original monograph, he had presented his new findings to the Westminster Medical Society. At the time medical journals often carried the proceedings of medical society meetings. Two weeks later the London Medical Gazette published the first half of a two-part report by John Snow, “On the Propagation and Mode of Communication of Cholera.”
By the time the second half of the report appeared a month later, on November 23, cholera had lost its grip on the city. After a high of more than 1,532 deaths during the week of August 7, cholera mortality declined steadily through the fall. During the last week of November, only one Londoner died of cholera. It was to be the final death of the epidemic.
Even after its disappearance, John Snow continued his work on cholera, but at a less frenzied pace. Cholera had disappeared for fifteen years after the last epidemic. To all parties it seemed there would be plenty of time for a full examination of the evidence and a reasoned debate on the prevailing theories.
Everyone had something to say on the subject. In just one issue, the London Medical Gazette carried reviews of seventeen different monographs on the causes and treatment of cholera, together with the first half of Snow’s article, and four other articles on the disease. Only Snow pointed the finger at drinking water.
Snow hoped that the many official reports on the epidemic, all written with far greater resources than he could muster, would unearth additional evidence to help prove his theory. But he underestimated the ability of those threatened by the truth to weave armor from twisted facts and distorted logic.
Snow understood that he was laying siege to the entrenched beliefs of the medical establishment, but their opposition paled in comparison to the financial and political forces marshaled against him. If Snow were proven correct about the ability of drinking water to transmit disease, the anticompetitive cartel that allowed London’s water companies to enrich their stockholders with little attention to water quality might crumble. If his belief that cholera was contagious were true, quarantines would have their ultimate justification, a conclusion that put him squarely at odds with the vast economic interests that relied on international trade. Ironically the greatest source of opposition to Snow’s ideas came from politicians bent on protecting the public health. Snow’s ideas put him on a collision course with a group that came to be known as the sanitarians. At their head was a great bull of a man whom John Stuart Mill called the most effective politician of his time. His name was Edwin Chadwick, and his perspective before, during, and after England’s second cholera epidemic in 1848–1849 was far different from Dr. Snow’s.