"I resolved to spare no exertion which might be necessary to ascertain the exact effect of the water supply on the progress of the epidemic."

JOHN SNOW, M.D., On the mode of communication of cholera, 1855

THE main burden of the tight against cholera in the British Isles had been borne by the humble, and usually underpaid, general practitioner. It was appropriate that the great discovery of how cholera was spread should have been made not by a high-powered official committee, or some flamboyant master of medicine, but by a shy, unfashionable doctor, who never achieved real eminence in his profession. Dr. John Snow had been born at York, the son of a farmer, in 1813, and at fourteen had been apprenticed to a surgeon in Newcastle. He had learned his trade in a tough school, as assistant to a succession of village surgeons, which involved "many rough rides and a fair share of night work."

In 1831 he had gained his first experience of cholera when he fought an epidemic at Kellingworth colliery single-handed. Five years later, like a nineteenth-century Dick Whittington, Snow set out for London on foot to make his fortune. For months he "walked the wards" at the Westminster Hospital, and in 1838, having qualified as a Member of the Royal College of Surgeons and of the Apothecaries Company, "nailed up his colors" as a general practitioner at his lodgings at 54 Frith Street, Soho.

Snow at this time was a very serious-minded young man, very different to the traditional medical student. His recreations were swimming, walking and collecting geological specimens and his idea of a merry Easter Monday was to challenge a fellow student to a fifty mile walking match. At the age of seventeen he had become both a teetotaller and a rigid vegetarian, though in later life he took an occasional glass of wine on social occasions, and he eventually abandoned his vegetarianism also. A fellow student described Snow in his early twenties: "Not particularly quick of apprehension, or ready in invention, he yet always kept in the foreground by his indomitable perseverance and determination.... The object of this steady pursuit with him was always truth."

Snow was by temperament quiet and reserved and many of his contemporaries considered him "peculiar." In his first years in London his practice did not prosper, largely, according to a friend, because he had "no personal introduction to the bedsides of dowagers" and there was "not the least element of quackery in all his composition." Snow supported himself from his fees as medical officer to four sick clubs, work involving many night calls and little pay, and filled in his time with research and study, ultimately adding both B.M. (Bachelor of Medicine) and M.D. (Doctor of Medicine) to his qualifications. The turning point in his career came in 1846, when ether began to be used in Britain as an anesthetic. This discovery, which was, in his own words, both "practical" and "humane," made an immense appeal to Snow, and soon he became recognized as an authority on it and its successor, chloroform. Before long his income had risen to 1,000 pounds a year and his name was finally made in 1853, when he was summoned to give chloroform to Queen Victoria at the birth of Prince Leopold — an occasion which convinced the doubters that it was not contrary to God’s will to reduce the pains of child-birth.

In 1848 Snow had turned his attention to cholera, for as an authority on respiration he had begun to doubt that it was conveyed by the air. He soon came to suspect that water was the responsible agent and the result was the first edition of On the mode of communication of cholera, which appeared in 1849. During the next six years "Dr. Snow’s theory" was frequently referred to but not generally accepted, partly no doubt because the miasmatists were so well entrenched, but also perhaps because Snow was not the man to command attention by force of personality. He was of no more than average height and slim build; his voice was husky and often hard to follow; and in the daily affairs of life he was punctilious to the point of fussiness, rising and retiring early and being exceedingly tidy in his habits. Snow lacked altogether the colourful touches that attract attention. He read nothing for pleasure except scientific works and was notoriously shy, the reason perhaps that he never married. His recreations in middle age were playing with his friends’ children, listening to his friend and biographer Dr. Richardson read aloud from Thackeray and Dickens, and occasionally going to the opera. In a profession whose leading members were often forthright to the point of rudeness, Snow was consistently reserved. He lacked altogether the ruthless determination that carries many men to the top. Often, says Richardson, he would make the long journey from Soho to Mortlake to see one of his friend’s poor patients, to the humblest of whom he was unfailingly courteous and kind. He was too compassionate, unlike many of his contemporaries, to carry out any experiment on an animal out of mere curiosity and, in an age of vigorous if not brutal controversy, too gentle ever to review a book critically: if he disapproved of it he refused to review it at all. All these features of his character help to explain why, when Dr. John Snow had at last found the truth about cholera, it took a generation for his ideas to be accepted.

The 1855 edition of On the mode of communication of cholera, in which Snow modestly offered his great discovery to the world, is virtually a different book from the previous essay with the same title and its 160 pages are a model of lucid exposition and convincing argument. Snow began by deducing certain basic facts about the disease. It had, he declared, nothing to do with the lungs, being in fact an "affection of the alimentary canal." It was the violent purging and vomiting which this produced which were the real clue to the disease for they led to the loss of fluid which caused all the other symptoms: the thick tarry blood, which made circulation difficult and thus caused the patient to feel cold, the weakened pulse and impaired breathing, the cramps, and even the dreaded collapse itself. From this introduction Snow went on to the root of the matter, the way in which cholera spread. "The morbid material producing cholera," he concluded, "must.., be swallowed accidentally, for persons would not take it intentionally." "Swallowed," that was the key word, and once it was accepted all else became plain. Cholera spread fastest among the poor, not because their homes were unventilated but because they were crowded and badly lighted. Under these conditions the other members of a patient’s family constantly came in contact, unknown to themselves, with the odorless and colorless "ejections and dejections" containing the cholera poison, and, since the poor rarely had facilities for washing, transferred it to their mouths when next they ate. At once the facts which had puzzled the world for twenty years were explained: the near immunity enjoyed by doctors, who washed before meals, and did not eat in their patients' homes; the liability to cholera of nurses and those who laid out the dead, who ate on the premises, and the infection of those who visited the sickroom or attended the funeral, occasions usually accompanied by food or drink. The cholera explosion in the child farm at Tooting in the 1848-9 epidemic was easily explained: the victims had been huddled together two or three in a bed, and like all children had constantly put their fingers in their mouths. The reason why the miners of Merthyr had suffered so badly was also clear. "The pitmen," wrote one of Snow’s informants, a relative connected with a Yorkshire colliery, "all take down with them a supply of food.... The pit is one huge privy and of course the men always take their victuals with unwashed hands."

All this was useful enough, but it was in the next section of his book that Dr. Snow made his vital contribution to medical knowledge. "If the cholera had no other means of communication he wrote, "it would confine itself chiefly to the crowded dwellings of the poor.... But there is often a way open for it to extend itself more widely and to reach the well-to-do classes of the community; I allude to the mixture of the cholera evacuations with the water used for drinking and culinary purposes, either by permeating the ground, and getting into wells, or by running along channels and sewers into the rivers from which entire towns are sometimes supplied with water." In these few lines the veil of mystery was at last ripped away from the disease which had bewildered governments and defeated doctors for a generation. Cholera was spread not by the air but by the water supply. The terrified mobs of St. Petersburg and Paris, who had raised riots and murdered strangers in the street, the fear-crazed peasants of Hungary who had stormed the castles of the nobility, all had alleged that they were being poisoned — and all had been right. But those responsible were not the sinister agents of some international conspiracy but themselves.

In support of his theory, Snow mustered an impressive array of evidence. There was, he pointed out, the significant case of the battalion of Native Infantry in India who had been stricken with cholera while on the march. "It was the belief of the natives..." reported a British doctor, "that the epidemic was the immediate consequence of the wrath of heaven, outraged and insulted by the pollution of certain sacred tanks... in which sepoys of low caste and camp followers had indiscriminately bathed" — the same tanks from which the troops had drawn their drinking water. There was the savage outbreak at the village of Newburn near Newcastle, the worst, in relation to population, of the whole 1831 epidemic. Snow, through correspondence with a friend in Newcastle and the vicar and surgeon at Newburn, succeeded, twenty years later and 300 miles away, in establishing its cause — a brook which, having been contaminated by the refuse of a village and a steel works, had half a mile further on infected a well. The outbreak in the Black Sea fleet was also full of clues for those with eyes to see them, a doctor on the spot having noted that the infected ships had drawn their drinking water three days before from a stream in which "soldiers, wearied by marching from a focus of cholera infection, were seen... washing their persons and clothing." 

The heart of Dr. Snow’s book lay in the seventeen pages in which he recorded his investigation into the affair of the Broad Street pump. Snow prepared a large-scale map of the area, with houses which had suffered cholera deaths indicated by black lines. The most casual glance showed at once the tremendous concentration of deaths in the immediate vicinity of the suspect pump, which enjoyed a high local reputation for taste and purity, and the virtual absence of deaths near the other eleven pumps in the district. "The result of the inquiry..." wrote Snow, "was, that there had been no particular outbreak or increase of cholera, in this part of London, except among the persons who were in the habit of drinking the water of the above-mentioned pump-well.... The deaths either very much diminished, or ceased altogether, at every point where it becomes decidedly nearer to send to another pump than to the one in Broad Street."  

Continue to Victory in Sight -- Part 2

Source: Longmate, Normal. Victory in Sight, Chapter 19, 201-211 in Longmate N. King Cholera  -- The Biography of a Disease, London,1966.

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