Great Scientists and their Inventions

Alexander Fleming (1881 – 1955.)

alexander fleming

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Alexander Fleming discovered penicillin, whose use has saved untold millions of lives. Less well-known is that before making this world-changing discovery, he had already made significant contributions to medical science.

Most Significant Contributions to Science

In 1914 World War 1 broke out and Fleming, aged 33, joined the army, becoming a captain in the Royal Army Medical Corps, working in field hospitals in France.

There, in a series of brilliant experiments, he established that antiseptic agents used to treat wounds and prevent infection were actually killing more soldiers than the infections were!

The antiseptics, such as carbolic acid, boric acid and hydrogen peroxide, were failing to kill bacteria deep in wounds; worse, they were in fact lowering the soldier’s natural resistance to infection because they were killing white blood cells.

Fleming demonstrated that antiseptic agents were only useful in treating superficial wounds, but were harmful when applied to deep wounds.

Almroth Wright believed that a saline solution – salt water – should be used to clean deep wounds, because this did not interfere with the body’s own defenses and in fact attracted white cells. Fleming proved this result in the field.

Wright and Fleming published their results, but most army doctors refused to change their ways, resulting in many preventable deaths.

Discovery of Lysozyme

In 1919 Fleming returned to research at St Mary’s Hospital Medical School in London. His wartime experience had firmly established his view that antibacterial agents should only be used if they worked with the body’s natural defences rather than against them; in particular, they must not harm white blood cells.

His first discovery of such an agent came in 1922, when he was 41 years old.

Fleming had taken secretions from inside the nose of a patient suffering from a head cold. He cultured the secretions to grow any bacteria that happened to be present. In the secretions, he discovered a new bacterium he called Micrococcus lysodeikticus, now called M luteus.

A few days later, Fleming was examining these bacteria. He himself was now suffering from a head cold, and a drop of mucus fell from his nose on to the bacteria. The bacteria in the area the drop had fallen were almost instantly destroyed. Always on the lookout for natural bacteria killers, this observation excited Fleming enormously.

He tested the effect of other fluids from the body, such as blood serum, saliva, and tears, on these bacteria and found that bacteria would not grow where a drop of one of these fluids had been placed.

Fleming discovered the common factor in the fluids was an enzyme.

He named his newly discovered enzyme lysozyme. The effect of lysozyme was to destroy certain types of microbe, rendering them harmless to people. The presence of lysozyme in our bodies prevents some potentially pathogenic microbes from causing us harm. It gives us natural immunity to a number of diseases.

However, lysozyme’s usefulness as a medicine is rather limited, because it has little or no effect on many other microbes that infect humans.

It did, however, mean that Fleming had discovered a natural antibiotic which did not kill white blood cells. If only he could find a more powerful antibiotic, then medicine could be transformed.

Today, lysozyme is used as a food and wine preservative. It is naturally present in especially large concentrations in egg-whites, offering protection against infection to chicks.

It is also used in medicines, particularly in Asia, where it is used in treatments for head colds, athlete’s foot and throat infections.

Discovery of Penicillin

In the month of August 1928, Fleming did something very important. He enjoyed a long vacation with his wife and young son.

On Monday, September 3, he returned to his laboratory and saw a pile of Petri dishes he had left on his bench. The dishes contained colonies ofStaphylococcus bacteria. While he was away, one of his assistants had left a window open and the dishes had become contaminated by different microbes.

Annoyed, Fleming looked through the dishes and found something remarkable had taken place in one of them.

A fungus was growing and the bacterial colonies around it had been killed. Farther from the fungus, the bacteria looked normal. Excited by his observation, he showed the dish to an assistant, who remarked on how similar this seemed to Fleming’s famous discovery of lysozyme.

Hoping he had discovered a better natural antibiotic than lysozyme, Fleming now devoted himself to growing more of the fungus. He identified that it belonged to the Penicillium genus and that it produced a bacteria-killing liquid. On March 7, 1929 he formally named the antibiotic – it would be known aspenicillin.

Fleming published his results, showing that penicillin killed a variety of bacteria which were then the scourge of humanity, including those responsible for scarlet fever, pneumonia, meningitis and diphtheria. Furthermore, penicillin was non-toxic and it did not attack white blood cells.

Unfortunately, the scientific world was largely underwhelmed, ignoring his discovery.

Award & Honour

In 1945 Alexander Fleming shared the Nobel Prize in Medicine or Physiology with Florey and Chain. The award was made:

“for the discovery of penicillin and its curative effect in various infectious diseases.”

In his Nobel Prize winning speech in 1945, Fleming warned of a danger which today is becoming ever more pressing:

Fleming was always fulsome in his praise for Florey, Chain, and their team, and he downplayed his own role in penicillin’s story. Despite his modesty, he became a worldwide hero. Millions of people owed their lives to the antibiotic he had discovered.


In 1953 Fleming married Dr. Amalia Koutsouri-Voureka, who was working in his research group at St Mary’s Hospital Medical School.

Alexander Fleming died aged 73 of a heart attack in London on March 11, 1955. His ashes were placed in St Paul’s Cathedral.


"One sometimes finds what one is not looking for." ~ Alexander Fleming

"It is the lone worker who makes the first advance in a subject; the details may be worked out by a team, but the prime idea is due to enterprise, thought, and perception of an individual." ~ Alexander Fleming