Major Medical Discoveries That Happened By Mistake

Over 900 Ranker voters have come together to rank this list of Major Medical Discoveries That Happened By Mistake
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Vote up the most surprising accidental medical discoveries.

Every year, millions of hours and billions of dollars are poured into medical innovation, with new methods of improving, sustaining, and extending human life discovered on a near daily basis - yet without some significant accidental medical discoveries thrown into the mix, many of us would not be here today.

Unintended scientific discoveries often prove more fascinating than those made on purpose. Perhaps it’s the lure of serendipity, or the enticing possibility of changing the world for the better through nothing more than sheer happenstance. Either way, people everywhere are grateful that some enterprising individuals were fortunate enough to stumble into important medical breakthroughs - and had awareness enough to understand the implications of their discoveries. 

  • The Coronary Angiogram Came About When A Catheter Slipped While A Cardiologist Was Treating A Patient
    Photo: Bleigass / Wikimedia Commons / CC BY-SA 3.0
    357 VOTES

    The Coronary Angiogram Came About When A Catheter Slipped While A Cardiologist Was Treating A Patient

    When F. Mason Sones Jr. accidentally invented the coronary angiogram (an X-ray to examine blood vessels), he didn’t just think he’d made a mistake - he thought he’d made a fatal error. At the time, the common belief was that contrast dye could be inserted into the larger vessels of the heart, like valves and chambers, but that putting it through the coronary arteries themselves would cause a lethal blockage.

    In 1958, Sones Jr. was overseeing the injection of dye into a patient’s aorta when the tube slipped into the right coronary artery, filling the vessel with contrast. Sones reportedly prepared for life-saving open-heart surgery, but the patient’s heartbeat - after a few ominous skips - kept chugging along. 

    Through further experimentation, scientists discovered that fears of blockages were overblown, and most patients could indeed manage a large amount of dye pushed through their arteries, leading directly to the invention of the coronary angiogram. 

    357 votes
  • The Implantable Pacemaker Was Invented When An Engineer Used The Wrong Resistor
    Photo: Professor Marko Turina / Wikimedia Commons / CC BY 3.0
    396 VOTES

    The Implantable Pacemaker Was Invented When An Engineer Used The Wrong Resistor

    Implantable pacemakers have greatly extended the lives of millions of individuals, but they might not have been invented if not for an idle-minded mistake. While working as a medical researcher in the 1950s, Wilson Greatbatch was putting together an oscillator when he reached into his toolbox and pulled out the wrong kind of resistor. He installed it into the oscillator without realizing, only to discover that it made the machine give off a rhythmic electrical pulse, giving Greatbatch the idea of a lifetime.

    Before his invention, pacemakers were enormous and unpleasant, capable of saving lives but not doing much to improve their quality. Greatbatch created a much smaller version of the device and tried inserting them into dogs. When that proved effective, he moved onto humans. It didn’t take long for their use to become mainstream, and they’ve remained so ever since.

    396 votes
  • 3
    348 VOTES

    Vaseline Was Once A Nuisance For Oil Rig Workers, But It Made Their Cuts Heal Nicely

    In 1859, out-of-work chemist Robert Chesebrough was visiting an oil field when he heard complaints about something called “rod wax” - a residue that built up in pumps and had to be periodically removed to prevent jamming. He also learned that rig workers had taken to collecting the jelly-like substance and applying it to their cuts and burns, reporting a soothing sensation, and that inspired Chesebrough to start experimenting.

    Over the next decade, he worked on extracting and purifying this petroleum jelly until he was left with a product suitable for the open market. Vaseline was the result, and Chesebrough spent the rest of his life extolling its medical virtues - reportedly going as far as to eat a spoonful of it a day himself. 

    348 votes
  • 4
    312 VOTES

    X-Rays Were Discovered During A Study Of Cathode Ray Tubes

    In 1895, Wilhelm Roentgen was performing a mundane experiment in Wurzburg, Bavaria - but the results he achieved were anything but. Roentgen was attempting to find out if cathode rays could pass through glass, so he covered a cathode tube with heavy black paper and waited to see what would happen.

    From within, an unnatural green light emerged through the paper and projected onto a nearby fluorescent screen, and that surprising result gave Roentgen an idea. He discovered that some of the rays he produced could pass through just about anything, but they also left shadows of solid objects on the screens they were projected onto. Because he didn’t know what these specific rays were, he labeled them “X-rays” - and the rest is history.

    312 votes
  • 5
    557 VOTES

    Penicillin Was Discovered When A Scientist Decided Not To Throw Out A Moldy Petri Dish

    The discovery of penicillin has made an enormous impact on the world, and is perhaps the most famous tale of accidental medical innovation in history - even if the commonly told version of the tale is a touch apocryphal. Alexander Fleming did not, as is commonly reported, leave a sandwich or some other item sitting in his lab while on vacation, only to return and find it molded over with a life-saving substance, but the truth is not far off.

    Fleming did go on vacation in 1928, and he did leave some items out in the lab, but they were Petri dishes filled with colonies of Staphylococcus. When he returned, he started examining them, including one that had grown moldy in his absence - and that’s when he made the discovery of a lifetime. The area of the dish affected by the mold, which Fleming later identified as Penicillium notatum, was free of the Staphylococcus, as if something in the mold itself was inhibiting the growth and spread of the bacteria. Soon enough, Fleming proved that that was exactly what was happening, and as a result penicillin is now the most widely used antibiotic in the world. 

    557 votes
  • The Pap Smear As A Way To Test For Cancer Was Discovered During A Study Of Changes During The Course of Sexual Development
    Photo: Dr. Roshan Nasimudeen / Wikimedia Commons / CC BY-SA 3.0
    439 VOTES

    The Pap Smear As A Way To Test For Cancer Was Discovered During A Study Of Changes During The Course of Sexual Development

    The Pap smear is one of the simplest procedures in modern medicine, yet one of the most vital for maintaining female health. It all stems from one doctor, George Papanicolaou, and his desire to understand the menstrual cycle. 

    At first, Papanicolaou only intended to swab his test subjects’ vaginas to determine how their vaginal cells changed at different stages of sexual development. But when he noticed cancer cells in one such swab, the focus of his research shifted - and he soon discovered that this simple, inexpensive procedure provided the earliest possible indications of cervical cancer in patients. In doing so, Papanicolaou undoubtedly saved countless lives, and today the method still bears his mercifully shortened name. 

    439 votes