It was said in the 19th century that no one who lived in London was ever wholly well. Some of the city's nicknames - the Oven, the Great Wen, the Stink, the Smoke, the Fever Patch - are tokens of its noisomeness. The city itself was deemed to be sick, an ague-ridden body with swollen limbs and contaminated blood. That is why, in Sick City, ooze, stench, putrefaction and decay are seen as part of the fabric of the capital. It is unnatural. It is fallen.

In this entertaining and sometimes edifying collection of essays, Richard Barnett charts the fevered history of London as a centre of disease and of cure. From his perspective the whole history of Western medicine can be seen in the crowded and unhealthy streets of the city. The original setting of the city, part marsh and part tributary, was malarial and stagnant. And the origin is important. The streets of Westminster are still subject to vapours from the river and the night. By the 16th century a dark pall from the smoke of sea-coal hovered above the capital. Fog was known to Dickens as the 19th-century “London particular”; it could rise 240ft above street level and was variously described as black, bottle-green, lurid brown and orange. This is the breath of sickness, the funereal wreath overhead.

The press of the multitude created an unnatural heat, a feverish acceleration of the pulse and an ever-aching head. The mass of the people emits many microbes; many germs are spread through close contact, and the whole citizenry of London can sometimes become a sick body. The Black Death of 1348 was only the most notorious epidemic of bubonic or pneumonic plague that descended on London every decade or so throughout the 14th century. It killed half the population. Plague was of the essence of London; it was its nature. It was an emanation of the city, seen in the shape of a miasma or mist uncurling above the rooftops.

That is why the Great Plague of 1665 has been largely understood as a London phenomenon. The sites of old plague pits are now poin-ted out with understandable pride. Richard Barnett reveals that the escalator at Camden Town Underground station passes through a vast grave for plague victims, and that a “massive plague pit” is responsible for the low ceiling of the basement of Harvey Nichols. It would be fair to say that he takes a certain, rather morbid, pleasure in compiling this Baedeker of disease and suffering. But why not? This is London's real heritage. Together with this volume are a glossary and six maps, so that the reader can make his or her way down the various roads to oblivion. If you wish to follow the course of tropical disease as it ate its way to the heart of the metropolis, you can do so; you can follow the route of the plague, or the life of an 18th-century medical student. All human life, and human death, is here.

There were four visitations of cholera in the 19th century. It was known as the “filth disease”, but Londoners have always been surrounded by filth. The smell of the city alone was enough to send shudders of anxiety among the populace. It was believed that all smell was disease, and so the scent of death was detected everywhere. It has been described as the smell of metal, or the smell of rain, or the smell of stone. It is in fact the intimate and yet cloying smell of human life and human activity. It is a primeval smell.

In the middle of the 19th century three million tonnes of horse dung were discharged each year on to the streets. In the “Great Stink” of 1858 the excrement of three million people ran directly into the Thames; the river became an open sewer and all natural life within its depths came to an end. The stink was so strong that Parliament was suspended. And there was another horror. The water supply for many Londoners was taken directly from the Thames; it was described as being a “brownish” colour.

London has always specialised in the theatre, and Barnett devotes much space to the doctor and patient as actors in an unending drama. The lunatics of Bedlam were, in the 18th century, put on display for spectators who paid a fee. The bodies of the sick were surgically treated in what were justifiably called “operating theatres”, with a semicircle of interested parties in attendance. The corpses of the dead were similarly anatomised in front of an audience. In London you always have to please the crowd.

But the city has also been driven by the twin imperatives of money and of power, and Barnett considers the practice of medicine as the expression or application of both principles. The doctors of the 18th and 19th centuries, like the quacks from whom they are not easily distinguished, healed for a fee; they muttered words of knowledge that were meant to calm or appease the sufferer; they dispensed pills or potions that were reassuringly expensive.

Yet alongside the distinguished practitioners there were also the devotees of older forms of healing. It is an odd fact of urban history that Londoners have been more susceptible to magic and superstition than even their country cousins. Every district of the city had its cunning man or wise woman. There were magical remedies for disease being propounded well into the 20th century, and may still remain. During the First World War, for example, it was customary in the East End to treat a sick child by cutting off some hair from the head, putting it into a sandwich and feeding it to the first dog that passed; it was believed that the illness would then enter the body of the unfortunate animal. The dog it was that died.

There is a chapter here on the history of madness in London, a fruitful subject of inquiry in a city where the bedlam of voices and people can cause fear and amazement in equal measure. The city itself has been seen as a gigantic asylum, with its inhabitants - or inmates - driven by one frenzy or another. Londoners were known throughout Europe, for example, for their tendency to suicide. Indeed, some foreigners made a pilgrimage to the city precisely in order to kill themselves. It was the capital of melancholy. To invert the phrase of Samuel Johnson, it was the place where you might easily grow tired of life. Melancholy and anxiety are still part of the texture of the city. Barnett reveals that “one in four residents of the modern city will receive treatment for some form of mental disorder during their lives”. That is perhaps why alcohol and other drugs have been imbibed in such enormous quantities here. They are the only ways of stilling the unceasing uproar of the city, and of fighting off the despair that life in the sick city can induce.

Sick City: 2,000 Years of Life and Death in London by Richard Barnett
Wellcome Trust/Strange Attractor, £15.99; 320pp Buy the book

Sick City will be Radio 4's book of the week for December 1-5, read by Tony Gardner

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