Serendipity has played a prominent part in many scientific discoveries

Fortunate unplanned discoveries include penicillin, Viagra, x-rays, radioactivity and microwave ovens

Serendipity is unplanned fortunate discovery and occurs commonly in scientific discovery and product invention. It has played a prominent part in the discovery of many drugs and medical treatments, including vaccination, insulin to treat diabetes, penicillin, quinine and Viagra; in many fundamental discoveries including x-rays, radioactivity, pulsars and the cosmic microwave background radiation; and in discovering many useful products such as teflon, vulcanised rubber, microwave ovens and velcro.

The best-known chance discovery in science is the 1928 discovery of penicillin by Scottish bacteriologist Alexander Fleming (1881-1955). Fleming was studying the Staphylococcus bacterium and noticed that a blue-green mould had contaminated a petri dish, killing off all the surrounding bacteria in the culture.

Earlier, in 1922, Fleming had accidentally shed a tear into a bacterial sample and noted that the spot where the tear landed was free of the bacteria that grew all around it. After conducting tests he concluded that tears contain an enzyme, lysozyme, that can fight off minor bacterial growth.

Six years later Fleming remembered his teardrop experience and concluded that the fungus growing in the petri dish was killing the powerful Staphylococcus bacteria. He isolated and identified the fungus as belonging to the genus Penicillium and named the active bacterium-killing agent secreted by the mould as penicillin.


Two other scientists, Ernst Chain (1906-1979) and Howard Florey (1898-1968), later purified and characterised penicillin, and publicised it widely as a non-toxic antibiotic capable of killing many bacteria that cause minor and severe infections in humans and animals.

Fleming declared: “But for the previous experience I would have thrown the plates away as many bacteriologists have done before.”

The discovery of penicillin is widely regarded as the birth of modern medicine. Fleming, Florey and Chain were jointly awarded the Nobel Prize in physiology or medicine in 1945.

Blood vessels

A modern example of serendipity in drug discovery is Viagra, Pfizer’s erectile dysfunction drug. The active agent in Viagra, sildenafil, was originally developed to treat cardiovascular problems by dilating blood vessels in the heart. Sildenafil worked moderately well in animal tests and was put into human clinical trial in the early 1990s.

The drug performed poorly in this trial, but an observant nurse noted something odd when checking on the men enrolled in the study – many of the men lay on their stomachs. The men were embarrassed because they had erections.

Dilation of blood vessels is a major part of the process that causes erection, and blood vessels were dilating in penises and not in hearts. A formulation of sildenafil (called Viagra) was approved by the USDA as an erectile dysfunction drug in 1998.

German physicist Wilhelm Roentgen (1845-1923) discovered x-rays in 1895 when examining the effects of passing electric current through partially evacuated glass tubes. The residual gas in the tubes glowed when current flowed but the glow was not visible in the darkened laboratory because Roentgen covered the tubes with black cardboard. However, he noted that a nearby fluorescent screen in the laboratory glowed each time the tubes were activated. Invisible rays coming from the tubes caused the screen to glow.

Roentgen systematically studied the rays, noting they had neither charge nor mass but had great penetrating power. He tried blocking the rays but many things placed between the tube and the screen made little difference. However, when he put his hand in front of the tube an image of the bones in his hand was projected onto the screen. Replacing the screen with a photographic plate recorded the first x-ray image.

Wounded soldiers

The potential of x-rays in medicine was immediately appreciated, and before the end of the century the British army was using mobile x-ray units to locate bullets and shrapnel in wounded soldiers. Roentgen won the 1901 Nobel Prize in physics.

Serendipity often opens up new unexpected territories and plays a role in scientific research analogous to mutations in biological evolution. However, the fruits of serendipity do not fall into a scientist’s lap like winning the Lotto.

Harvesting the serendipitous observation requires the application of a keen scientific mind. As Louis Pasteur (1822-1895) observed sagely: "In the fields of observation, chance favours only the prepared mind."

An observation by movie tycoon Sam Goldwyn (1882-1974) is also pertinent: "The harder I work, the luckier I get".

William Reville is an emeritus professor of biochemistry at UCC