The history
4,500 years from covered drains in the Indus cities to urea made in a flask, a light inside the bladder and a salt-and-sugar drink that saves millions.
For most of history people could only look at what the body threw away: physicians held urine up to the light and guessed. Weighing, then chemistry, showed where the waste really comes from: carbon dioxide in the breath, urea from protein, water through the skin. Meanwhile engineers and campaigners learned that getting waste safely away from people matters as much as making it, from sewers and flush toilets to India's toilet mission and oral rehydration salts.
c. 2600 BCE
City-wide covered drains
Indus Valley cities
1614
Insensible water loss measured
Santorio Santorio, Italy
1750s
Carbon dioxide shown in the breath
Joseph Black, Scotland
1828
A body chemical made from non-living ones
Friedrich Wöhler (urea), Germany
1877–1879
Practical cystoscope
Maximilian Nitze and Josef Leiter
1932
First metabolic cycle discovered
Hans Krebs and Kurt Henseleit (urea cycle)
1956
Dip-and-read urine test strip
Helen and Alfred Free, USA
2600 BCE – 1640
Ancient cities built drains, and for two thousand years doctors judged health by the colour of urine in a glass flask.
2500 BCE
c. 2600–1900 BCE
Many houses in the Indus Valley cities had a bathing floor and a toilet that drained into covered brick channels along the streets. It was one of the earliest city-wide drainage systems anywhere.
Why it mattered. Carrying waste away from homes is one of the oldest public-health ideas of all.
650
7th century (dates uncertain)
The Byzantine physician Theophilus wrote De Urinis, often called the first text devoted only to urine. It taught doctors to judge illness by its colour, cloudiness and sediment.
Why it mattered. It set the pattern of medieval uroscopy for centuries.
1200
c. 1200
Gilles de Corbeil wrote a teaching poem linking about twenty kinds of urine to illnesses. The matula, a bladder-shaped glass flask, became the symbol of physicians in paintings for centuries.
Why it mattered. People already sensed that urine reports on the body, even if they read it wrongly.
1506
Pinder's Epiphanie Medicorum printed a wheel of twenty flasks of different colours, each tied to a diagnosis. Such colour charts were popular in early printed medical books.
Why it mattered. A colour chart for urine returned, this time with evidence behind it, in the 1990s.
1637
Brian's book mocked doctors who claimed to diagnose anything from a flask of urine without ever seeing the patient. Uroscopy slowly lost its standing.
Why it mattered. Medicine began asking for evidence rather than tradition.
1590 – 1900
Flush toilets, traps and sewers carried waste away, and cholera showed why it mattered.
1596
Harington built a toilet with a cistern that flushed the bowl, and described it in a joke-filled book called The Metamorphosis of Ajax. Few copied it for almost two centuries.
Why it mattered. The idea of washing waste away with water came long before the pipes did.
1775
Cumming patented a toilet with an S-shaped trap under the bowl. The water sitting in the bend blocks smells from the drain.
Why it mattered. Every flush toilet still uses a water trap.
1854
Snow mapped cholera deaths in Soho and traced them to one water pump, whose well was polluted by a nearby cesspit. When the handle was removed the outbreak was already fading, but his evidence stuck.
Why it mattered. It showed that human waste in drinking water spreads deadly disease.
1859
1859–1875
After the smelly summer of 1858, Parliament paid for a network of brick sewers that carried waste far downstream. Its main parts were finished by 1875 and are still in use.
Why it mattered. Cities learned that sanitation is infrastructure, like roads.
1610 – 1940
Scales and test tubes found the real wastes: water lost through the skin, carbon dioxide in the breath, urea and uric acid, and the cycle that makes urea.
1614
Santorio weighed himself, his food and his waste for about 30 years, often sitting on a weighing chair. Much of what he ate never left as visible waste; he called it insensible perspiration, lost through the skin and breath.
Why it mattered. It was the first measurement of the water we lose without noticing, about 0.7 litres a day.
1757
1750s
Black studied a heavy gas he called fixed air, now called carbon dioxide. Breath bubbled through lime water turned it cloudy, showing that animals breathe the gas out.
Why it mattered. It identified the biggest waste the body makes, about 1 kg a day.
1773
Rouelle evaporated urine and treated it with alcohol to get crystals of a new substance. In 1799 Fourcroy and Vauquelin named it urea.
Why it mattered. Urea turned out to be the main way people get rid of nitrogen.
1776
Scheele isolated a new acid from kidney stones. Uric acid was later found to be the main nitrogen waste of birds and reptiles.
Why it mattered. It revealed that animals get rid of nitrogen in different forms.
1783
1777–1783
Measuring the heat and carbon dioxide from a guinea pig in an ice calorimeter, they argued that breathing is a slow combustion: food burns with oxygen and leaves carbon dioxide.
Why it mattered. It explained where the carbon dioxide we breathe out comes from.
1828
Wöhler heated ammonium cyanate, a salt made from non-living chemicals, and got urea, a substance until then made only by living bodies. It surprised even him.
Why it mattered. It helped end the belief that the chemistry of life follows special rules.
1833
With an improved microscope, Purkyně described the coiled sweat glands in the skin. We now know there are about 2 to 4 million of them.
Why it mattered. It showed the skin as an organ that moves water and salt out of the body.
1932
Working with thin slices of liver, Krebs and his student Henseleit showed that ornithine is used and then given back as ammonia is turned into urea. It was the first metabolic cycle ever found.
Why it mattered. It explained how the liver makes toxic ammonia safe.
1870 – 1995
Doctors learned to see inside the bladder, drain it safely, test urine with a strip of paper and find the brain's bladder switch.
1877
1877–1879
Nitze showed his first cystoscope in Dresden in 1877, lit by a glowing platinum wire cooled with water. With the Viennese instrument maker Leiter he made a practical version, first shown on a patient in 1879.
Why it mattered. Doctors could finally look inside the bladder instead of guessing.
1925
Barrington found a small area in the brainstem of cats that, when damaged, stopped normal emptying of the bladder. It is now called Barrington's nucleus, or the pontine micturition centre.
Why it mattered. It located the “go” switch that your cortex learns to hold.
1937
1930s (published 1937)
Foley designed a soft tube with a small balloon near its tip that is filled inside the bladder to hold it in place. C. R. Bard made it and named it after him.
Why it mattered. It is still the standard way to drain a bladder in hospital.
1953
1953–1954
Du Vigneaud worked out and built oxytocin and then vasopressin, the antidiuretic hormone that tells the kidneys to keep water. He won the 1955 Nobel Prize in Chemistry.
Why it mattered. It put a structure to the body's water-saving signal.
1956
The Frees and their team made Clinistix, a paper strip that changes colour when dipped in urine containing glucose. Strips for many other tests followed.
Why it mattered. Urine testing became quick, cheap and possible at home.
1994
Armstrong's team showed that an 8-shade chart of urine colour tracks how concentrated it is, well enough to guide how much athletes drink. Looking at urine came back, this time with evidence.
Why it mattered. It gave everyone a simple check on hydration.
1965 – today
A cheap drink stopped dehydration from killing so many children, and India built toilets on a scale never seen before.
1968
1967–1968
Trials showed that even people with severe cholera can absorb a drink of glucose, salt and water, because sugar carries sodium, and water follows, into the gut wall. It cut the need for drips by about 80%.
Why it mattered. It turned rehydration from a hospital job into something a parent can do.
1970
Pathak founded the Sulabh movement and spread a cheap two-pit pour-flush toilet that needs no sewer: one pit fills while the other turns safely into manure. Sulabh went on to build over a million household toilets.
Why it mattered. It helped end manual scavenging and showed that clean toilets can be affordable.
1971
During the Bangladesh war, drips ran out in camps where cholera spread. Mahalanabis's team gave oral rehydration solution to more than 3,000 patients; deaths fell to about 3.6%, against about 30% with drips alone.
Why it mattered. It proved ORS works in the hardest conditions, and the world took notice.
1978
A Lancet editorial called the discovery that glucose speeds the absorption of salt and water potentially the most important medical advance of the century. WHO and UNICEF were spreading ORS packets worldwide.
Why it mattered. A cheap packet became one of the great life-savers of the 20th century.
2002
After trials, WHO recommended a new ORS with less salt and sugar (245 instead of 311 mOsm/L). It cuts stool output in children by about a quarter.
Why it mattered. The same idea, fine-tuned, works better for children.
2014
2 October 2014
India launched a five-year mission to end open defecation. By 2 October 2019 all states had declared themselves open-defecation free, after more than 100 million household toilets were built in villages.
Why it mattered. It was the largest toilet-building programme in history.
By the numbers
WHO/UNICEF Joint Monitoring Programme estimates (via Our World in Data) of the share of India's population practising open defecation. It fell fastest during the Swachh Bharat years.
Did you know?
You breathe out about 1 kg of carbon dioxide a day. Most of the fat you lose when you slim down leaves this way, as carbon in your breath.
Urea was the first chemical from a living body to be made from non-living ones, in 1828.
Fish can get rid of plain ammonia because they live in water; birds make a nearly dry paste of uric acid instead, saving water and weight.
Brown stool and yellow urine both get their colour from the breakdown of old red blood cells.
Oral rehydration salts are on the WHO list of essential medicines, and a packet costs very little.
The people
1561 – 1636 · Physician · Venetian Republic (today Italy and Slovenia)
Weighed everything that went into and came out of his body for decades, and found the water we lose without noticing.
1800 – 1882 · Chemist · Germany
Made urea from non-living chemicals in 1828.
1900 – 1981 · Biochemist · Germany, later England
Found the urea cycle in 1932 and the citric acid cycle in 1937; Nobel Prize 1953.
1848 – 1906 · Urologist · Germany
Built the first practical cystoscope, a telescope with its own light for looking inside the bladder.
1923 – 2021 · Chemist · USA
Co-developed the dip-and-read urine test strips that made testing quick and cheap.
1934 – 2022 · Paediatrician · India
Proved oral rehydration works in a cholera epidemic in the 1971 refugee camps; awarded the Padma Vibhushan after his death.
1943 – 2023 · Sociologist and sanitation reformer · India
Founded Sulabh International and spread the cheap two-pit pour-flush toilet.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
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