its origins and how it changed medicine forever

Bubonic plague, smallpox, rabies or syphilis are some of the diseases for which no cure would be found without the microscope. In some cases directly, as when the German Robert Koch (1843-1910) was able to identify for the first time Mycobacterium tuberculosis, which is behind most cases of tuberculosis in the world. The Swiss Alexandre Yersin (1863-1943) did the same with Yersinia pestiswhich causes bubonic plague.

On the other hand, it is true that Louis Pasteur (1822-1895) did not need to see any of the viruses Rhabdoviridae to find a vaccine against rabies. However, in an indirect way, the microscope was there, the key to the formulation of the germ theory of disease. That is, in the discovery that microorganisms (viruses, bacteria, fungi…) are the cause of a wide range of conditions. If in the 16th century the Italian physician Girolamo Fracastoro (1478-1553) already suspected that some “living agents” were behind the diseases, Pasteur could see it with his own eyes.

I wouldn’t do it with the naked eye. According to the Institut Pasteur, a human being can at most perceive an object measuring one millimeter at a distance of three meters. While not bad at all, it’s not enough to see bacteria that range in size between 0.5 and 5 micrometers in length. Very small, considering that a micrometer is one-thousandth of a millimeter. And what about viruses, about 100 times smaller (there are smaller ones), for which optical microscopes are not enough.

So someone could see Rhabdoviridae Pasteur had to wait until 1962 and the invention of the electron microscope. But what’s fascinating about this story isn’t the heart-stopping numbers that today’s computers log in millions of increments. The real Rubicon was crossed when scientists discovered the world of what micro: close but so far unseen.

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Bernard Mendoza

This does not mean that the optical properties of lenses and even water were not already known in classical Greece. In fact, by the thirteenth century, spectacles, magnifying glasses, and glasses of all kinds were already tools in common use.

Otherwise, the Dutch mathematician Willebrord Snell van Rooyen (1580-1626) could not have confirmed in 1621 that light rays do not travel at the same speed in air as they do through water or glass. To notice this phenomenon, it is enough to observe the shape that a pencil appears to take when immersed in a glass of water. This is the principle of refraction, the same one that was first used in the 17th century to deform light rays through lenses to enlarge the image of an object.

It was the first microscope. In its simplest form, it was a lens (optics) that was placed as close as possible to the object of study in order to lose as little clarity as possible. Said light passed through the interior of a cylinder, at the end of which was an eyepiece through which the observer saw the magnified image.

But who invented it? The truth is that historians are still lost in multiple candidates, including Galileo Galilei (1564-1642). But it is not his name that recurs most often, but that of Zacharias Jansen (c. 1583-c. 1638). A traveling salesman by trade, more than an inventor, this Dutchman should be considered a survivor. In 1618 he had to flee from Middelburg after being caught forging coins, and he did not last long in his new residence, from which he had to flee again for the same crime a few years later.

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Amongst so much running, he also seems to have had time to assemble a nine-magnification microscope, that is, one that magnifies the size of any object nine times. At least that’s what his son told Willem Boreel (1591-1668), a Dutch diplomat who led an investigation to discover the device’s rightful creator in 1655. In turn, Jansen Jr. took advantage of the visit to expose that Hans Lipperschey (c. 1570-1619) stole the idea from his father.

Another one? Indeed. And for Boreel, another part of an investigation that had gotten off to a bad start. And this is that as early as 1619, during a visit to London, an engineer named Cornelius Drebbel (1572-1633) showed him a microscope of his own manufacture.

With this device, the only thing that can be clarified is who named it. This was Giovanni Faber (1574-1629), a member of the Italian National Academy of Painting. From Greek microphones (small) and with scope (look), came to him after seeing one in the possession of another fellow lynx, Galileo.

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Xavier Villatella Ortiz

Bayer Aspirin

Nothing more. In this case, however, perhaps the identity of the inventor does not matter much. Those who really made the microscope a landmark were the British, Italian and Dutch naturalists who, from the 1660s, began using it to observe nature up close.

The Englishman Robert Hooke (1635-1703) did it with almost anything he could. Insects, animal tissues, plants, fossils or mold pass through its stage. He then gathered his research Photomicrograph (1665), the first publication to contain detailed illustrations of microscopic observations.

Among other things, he described for the first time the structure of snow, ice or crystals present in urine. Although the most famous of this book is the use of the term cell, the first. He came up with it after observing the dead cells on a cork leaf. From Latin cellulaethat is, cells, he gave them that name because they reminded him of those of a beehive.

Although more spectacular is what was achieved by the Dutchman Anton van Leeuwenhoek (1632-1723). After making a 200x microscope with his own hands, this self-taught man found himself observing almost everything. He was the first to describe protozoa, bacteria, sperm or red blood cells.

As innovative as it was, his descriptions raised quite a few concerns at the Royal Society of London, especially coming from a man without a university education. Perhaps this is the key, as he was not affected by the prejudices of his fellow doctors, brought up on certain premises that later proved to be false.

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Xavier Villatella Ortiz

Photo of Frida Kahlo included in correspondence sent to Josep Bartoli

Above all, the ancient belief that pathogens arose spontaneously from organic and inorganic matter (spontaneous generation hypothesis) or that evils came from fetid emanations from the soil (miasmatic theory of disease). Older than these is the theory of humors, which since ancient Greece dictates that disease comes from an imbalance between the humors of the body (sputum, blood, black bile and yellow bile).

Although these theories dominated medicine until the 19th century, the discovery of viruses, bacteria and fungi rendered them obsolete.

Micrograph taken with a scanning electron microscope of the bacterium

Micrograph taken with a scanning electron microscope of the bacterium “Streptococcus pneumoniae”


Van Leeuwenhoek called them “animalcules,” but he meant bacteria. The same ones that Pasteur observed a century later and which allowed him to discover the first pathogenic agents. Shortly thereafter, in 1876, Robert Koch was able to show that one of them, Bacillus anthraciswas the cause of anthrax.

And so was born the germ theory of disease that changed the history of medicine. But the contribution of the microscope does not end there. In 1931, the Germans Max Knoll (1897-1969) and Ernst Ruska (1906-1988) expanded its capabilities by using an electron beam instead of light to focus the sample. With the electron microscope, they could magnify up to 100,000 times what they were observing. It seems like a lot, but today there is already equipment that allows you to see atoms!

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