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The Man with a Map

Medicine isn’t the oldest profession, but it goes back thousands of years. Being a doctor was a respectable profession in which you could earn a lot of money and gain entry to the highest levels of society. And yet for most of that time, being a doctor was pretty much useless. In fact, doctors were often dangerous to their patients.

They didn’t understand the human body and the drugs they used were often poisonous. If you were rich and could afford the best treatment, you were often worse off than someone poor who stayed in bed, receiving help from an uneducated relative or friend.

When George IV went mad, his doctors had no real idea how to cure him. But they spent a lot of money on treatments. And look at medical techniques like bleeding. It was once common for a doctor to open the vein of a sick person and run off a quantity of blood, to “re-balance” fluids in the body. If the patient died, then obviously the illness or injury was too severe for even a doctor to treat successfully. If the patient lived, then the doctor got the credit, even though, in reality, he had harmed rather than helped the patient.

Medicine didn’t stop being a menace until doctors began to understand the human body and disease better. One of the biggest steps was the realization that infections were caused by living things that were too small to see. That once seemed a crazy idea. How could something too small to see kill a healthy human being? Doctors preferred to think that bad air or diet had thrown the natural harmony of the body off balance. They were wrong, because the world has often proved much stranger than we think. Diseases like cholera were indeed caused by tiny living things, rather than by bad air interfering with the body’s workings.

This mistaken idea led medical science astray for a very long time. It wasn’t until the middle of the nineteenth century that a clever and far-sighted doctor called John Snow made a great stride towards the truth. And all he used was a map. In 1854, cholera broke out in a poor district of London. Doctors thought the cause was obvious: the air in the district was bad, contaminated by rotting rubbish and a faulty sewage system. No wonder people fell sick when they had to breathe such disgusting stinks!

Dr Snow didn’t agree. He thought the cause was more direct: it was something in the water people were drinking that made them fall ill, not in the air that they breathed. He began to record cases of cholera on a map and measure how far they were from sources of water. In the end, he narrowed down a pump on Broad Street as highly suspicious. Those who drank its water were much more likely to catch cholera. But workers at a local brewery weren’t falling ill, even though they lived very near the pump. Why not? Dr Snow investigated further and discovered that the brewery gave its workers free beer, so they didn’t use the pump.

The evidence he gathered was very strong. He argued that cholera was transmitted in contaminated water, not by foul air. That made good sense: cholera caused vomiting and diarrhoea, which then entered the sewers. If the sewers leaked into wells and contaminated the water there, drinking the water would infect more people with cholera. Dr Snow took his evidence to the authorities and the handle on the Broad Street pump was quickly removed, helping to end the outbreak of cholera.

It was one of the biggest advances in medical history and Snow had done it with nothing more than a map and some clear thinking. He still didn’t know that cholera was caused by bacteria, but he had pointed the way for future research. Later in the century, the great French scientist Louis Pasteur would advance the “germ theory” of disease, proposing that tiny living creatures could invade and infect the human body. His idea was soon widely accepted, overturning many centuries of ignorance and helping medicine become a proper science. As they understood more about disease and the human body, doctors could begin to help their patients rather than harm them.