Antonie van Leeuwenhoek is the somewhat improbable father of microbiology. A moderately educated owner of a textile business, he learned how to make his own unique microscopes which offered unparallelled magnification. Using these microscopes he made a number of crucially important scientific discoveries, including single-celled animals and plants, bacteria, and spermatozoa.
His microscopy methods were so finely tuned that after he discovered bacteria, this type of organism would not be observed again by any other scientist for over 100 years.
Antonie van Leeuwenhoek was born on October 24, 1632, in the small city of Delft in the Dutch Republic. His father was Philips Antonisz van Leeuwenhoek, a basket maker. His mother was Margaretha Bel van den Berch, whose prosperous family were beer brewers.
Antonie’s early life was rather rocky: his father died when he was just five years old. His mother remarried, and Antonie spent some time living with an uncle. His uncle was a lawyer and helped Antonie with basic literacy and numeracy, reinforcing the education he had received in local schools. By the time Antonie was 16, his step-father had also died.
Antonie learned no languages other than Dutch, which suggests he was never expected to go to university: he would have needed to learn at least Latin for this.
In 1648, at the age of 16, Leeuwenhoek moved to the famous Dutch trading city of Amsterdam to begin work in a textile shop. He learned his trade well and was promoted to the trusted position of cashier and book-keeper.
In 1654, aged 21, he returned to Delft, where he would spend the rest of his long life. This was a significant year for Leeuwenhoek. Not only did he return to his hometown, but he got married, and, putting his business experience in Amsterdam into practice, he opened his own textile shop in Delft. In addition to cloth he sold buttons, ribbons, and other accessories.
Over the next few years Leeuwenhoek became an influential figure in Delft. In 1660, aged 28, he was appointed to manage the operations of Delft’s council meeting hall. In return for only a small amount of work – the actual physical work of the job was delegated to other people – he received a generous salary.
A man of many talents, Leeuwenhoek was also appointed to supervise Delft’s wine trade and levy the appropriate taxes on imported wine.
While running his shop and working for the city of Delft, Leeuwenhoek became a qualified land surveyor at about 40 years of age, just before he started his scientific work.
Antonie van Leeuwenhoek’s Science
The Discovery of the Leeuwenhoek Lens
Leeuwenhoek’s biological discoveries were completely dependent on his ability to make lenses of extraordinarily high quality.
He never told anyone how he made his lenses. The secret went with him to the grave. In fact, to throw competitors off the scent, he used to talk about how he had to grind glass for a very long time to make his lenses. This was almost certainly not true.
People in the textiles trade had, for hundreds of years, used glass pearls – small spheres of glass – as lenses to examine cloth in fine detail. Leeuwenhoek used glass pearls frequently in his day-to-day business to examine the density of threads and the quality of cloth.
In 1665 the great English scientist Robert Hooke released Micrographia, showcasing drawings he had made of the natural world seen through the lens of his microscope.
Leeuwenhoek visited England in 1668 and most likely saw a copy of Micrographia: it had become the first scientific bestseller. Importantly for Leeuwenhoek, it contained drawings Hooke had made of his microscopic examinations of cloth.
Micrographia contains a description of how a powerful microscope could be made using a single spherical lens – similar to the glass pearls Leeuwenhoek was already familiar with:
…if you take a very clear piece of a broken Venice Glass, and in a lamp draw it out into very small hairs or threads, then holding the ends of these threads in the flame, till they melt and run into a small round globule, or drop, which will hang at the end of the thread; and if further you stick several of these upon the end of a stick with a little sealing wax, so as that the threads stand upwards, and then… grind off a good part of them, and afterward on a smooth metal plate, with a little tripoly, rub them till they come to be very smooth; if one of these be fixed with a little soft wax against a small needle hole, pricked through a thin plate of brass, lead, pewter, or any other metal, and an object, placed very near, be looked at through it, it will both magnify and make some objects more distinct then any of the great microscopes.
(In Hooke’s day people sometimes wrote VERY long sentences indeed!)
We cannot tell whether Leeuwenhoek was aware of Hooke’s words – he could not read English. However, it is now believed that he used Hooke’s technique to make his lenses.
Hooke himself did not use lenses made by this method because they were inconvenient: the distance between the lens and the viewed object had to be very short and the observer’s eye had to be pushed very close to the lens, causing Hooke’s eyes to quickly become strained.
Hooke used a compound microscope (one with two lenses) which more closely resembles the microscopes we use today.
Leeuwenhoek, however, was more than happy to use small, spherical lenses to make single-lens microscopes. He kept the details of how he manufactured his lenses secret, but today we can be reasonably sure that he did the following:
- used a hot flame to heat the middle part of a glass rod until molten
- pulled the ends of the rod in opposite directions, forming a long, thin thread of molten glass
- continued pulling the ends while the molten thread in the middle grew thinner and thinner, finally breaking
- placed one of the thread ends back into the flame, resulting in the end of the thread forming a small glass sphere
This sphere was a lens, which may have required some polishing. The smaller the sphere, the greater the magnification.
When he started making lenses, Leeuwenhoek may have hoped to use them to examine textiles more closely than anyone had ever done before.
Soon, however, he felt the same compulsion as Hooke to examine natural objects in never-before-seen detail.
Microscopes made from Leeuwenhoek’s tiny spherical lenses – the smallest lenses measured just 1 mm across – were easily capable of magnifying objects by a factor of about 200 – 300, while Hooke’s compound microscope magnified only by a factor of about 40 – 50.
Remarkably, Leeuwenhoek could use his lenses to resolve details as small as 1.35 μm. (This meant that, for example, he could easily see red blood cells, which are typically 6 – 8 μm in diameter.)
What is still uncertain even today is how Leeuwenhoek lit the objects he was studying. This was a vitally important part of his unique art of microscopy. Another was his unrivaled skill in setting up for viewing:
- drops of liquid, such as blood or pond-water, or
- solid samples, such as plant material or animal muscles, cleanly cut with a razor blade into very thin sections, transparent enough for light to travel through so their details could be seen and drawn.
Leeuwenhoek made over 500 tiny microscopes during his lifetime. They were awkward to use and inconvenient, which is why today we use compound microscopes. Despite their drawbacks, in Leeuwenhoek’s expert hands, they revealed an entirely new biological world.
The Microscopic World Discovered by Leeuwenhoek
Leeuwenhoek was a tradesman who had no formal training in science and had never been to college.
Nevertheless, the quality of his observations was so high and his discoveries so compelling that his research became well-known through letters he sent to the Royal Society in London. These were translated into English and published in the Society’s journal, Philosophical Transactions.
Interestingly, many of Leeuwenhoek’s letters were read first by Robert Hooke, who was the Curator of Experiments and then Secretary of the Society. Hooke actually learned Dutch so he could read Leeuwenhoek’s letters for himself.
Leeuwenhoek’s first communication was in 1673, replicating some of the work Hooke had covered in Micrographia, including Leeuwenhoek’s detailed drawings of bee stings, a fungus, and a human louse.
The following year Leeuwenhoek began to describe outstanding new discoveries he had made.
In 1674, aged 41, Leeuwenhoek made the first of his great discoveries: single-celled life forms. Nowadays these organisms are grouped with the protists – these are mainly single-celled plants and animals. Echoing the initial disbelief Hooke’s Micrographia had met, many members of the Royal Society refused to believe in the existence of Leeuwenhoek’s microscopic creatures. It took until 1677 before their existence was fully accepted. This happened after Robert Hooke returned to his microscopes, which he had given up because of eye strain, and verified Leeuwenhoek’s observations.
The Shape and Size of Red Blood Cells
In 1674 Leeuwenhoek examined red blood cells, which had been discovered six years earlier by his fellow Dutchman, Jan Swammerdam. With his superior lens, Leeuwenhoek was able to give a clearer description of the cells than ever before and was the first person to determine their size accurately.
In 1676 Leeuwenhoek discovered bacteria in water. The bacteria were at the limit of observation of his microscope – he estimated that it would take more than 10,000 of them to fill the volume of a small grain of sand. Such was the brilliance of his work that nobody else observed bacteria until another century had passed.
In 1677 Leeuwenhoek discovered spermatozoa, later concluding that eggs are fertilized when entered by sperm.
In 1683 Leeuwenhoek discovered the lymphatic capillaries, which contained “a white fluid, like milk.”
By observing the life-cycles of maggots and fleas Leeuwenhoek proved that such creatures are not spontaneously generated, as many people believed at the time. He showed these creatures go through a process of reproduction from eggs to maggots to pupae to adults.
By dissecting aphids he discovered parthenogenesis. He found parent aphids containing the embryos of new aphids although eggs had not been fertilized.
By observing the flow of blood in tiny capillaries, Leeuwenhoek confirmed William Harvey’s work on blood circulation.
The Birth of a New Science
Leeuwenhoek’s discoveries, combined with Hooke’s earlier discovery of microscopic fungi, signaled the creation of a new science: microbiology.
Some Personal Details and The End
Leeuwenhoek married Barbara de Mey in 1654, when he was 21 years old. They had five children, but only one – their daughter Maria – survived beyond infancy.
Barbara died in 1666, after twelve years of marriage. Five years later Leeuwenhoek married Cornelia Swalmius, with whom he had no children. It was during his second marriage that Leeuwenhoek’s interest in science seems to have developed.
In February 1680 Leeuwenhoek was elected to The Royal Society in London. He took great pride in this; it meant that he had won recognition as a true scientist. He never visited the Royal Society. He was happy to continue his work in Delft.
Leeuwenhoek’s second wife, Cornelia, died in 1694, when Leeuwenhoek was 61 years old.
Antonie van Leeuwenhoek died aged 90 on August 26, 1723. He was buried in the Old Church in Delft.
Although he had not been born into a scientific family nor had he received an education in science, his death was that of a true scientist. He communicated to the Royal Society such a careful, detailed description of the medical condition that was affecting him, eventually causing his death, that it is now called Van Leeuwenhoek’s disease. This is a rare condition which causes involuntary twitching of muscles.
Leeuwenhoek was survived by his daughter Maria, who had not married. She looked after her aging father and helped him to run the family’s textile business. Leeuwenhoek had become a wealthy man and Maria inherited this wealth.
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The Select Works of Antony van Leeuwenhoek
The Philanthropic Society, London, 1807
Antony van Leeuwenhoek and his “Little animals”
Harcourt, Brace and Company, New York, 1932
Review of the Leeuwenhoek Legacy
The Quarterly Review of Biology, Vol 69, (1) March 1994
The Discovery of Microorganisms by Robert Hooke and Antoni van Leeuwenhoek, Fellows of the Royal Society
Notes Rec. R. Soc. Lond. 58 (2), 2004
Robert Hooke’s Micrographia of 1665 and 1667
J R Coll Physicians Edinb (40) 2010
Creative Commons licensed images
Image of Antonie van Leeuwenhoek at Microscope from the Wellcome Trust, Creative Commons Attribution 4.0 International.