Antoni van Leeuwenhoek

Dutch inventor and scientist

• Born: October 24, 1632
• Birthplace: Delft, Holland, United Provinces (now in the Netherlands)
• Died: August 26, 1723
• Place of death: Delft, Holland, United Provinces (now in the Netherlands)

Leeuwenhoek discovered a new world of living organisms never before seen by human eyes after he made the undeveloped microscope a significant tool for scientific research. Considered the founder of modern microscopy, his microscope was used for more than two centuries because of its accuracy.

Early Life

Antoni van Leeuwenhoek (ahn-TOHN-ee vahn LAY-vehn-hewk) was the son of a basket maker, Philips Antonyszoon van Leeuwenhoek, and Margaretha. Antoni’s father died when the boy was about seven, and about two years later his mother remarried. About that time, young Leeuwenhoek was sent to school at Warmond, just north of Leiden. Subsequently, he lived with an uncle, who was a lawyer serving as town clerk of Benthuizen.

Leeuwenhoek’s early education must have provided a good foundation in geometry, trigonometry, and natural science, but his later writings show that he had received no instruction in Latin or modern foreign languages, and thus he had never been intended for the university.

At the age of sixteen, Leeuwenhoek was sent to Amsterdam to learn the cloth trade. After some six years, he returned to Delft as a draper, residing there for the rest of his life. In 1660, he was named chamberlain of the city hall. It was a well-paying sinecure, leaving him with a fair income, even after hiring the personnel and supplies necessary to clean, heat, and light the building.

Testifying to his mathematical ability, he was made municipal surveyor in 1677, and in 1679, he was named inspector of weights and measures. Eventually, as a result of his microscopy, he would become an “institution” in Delft, and the city would award him a special pension. As time went on, Leeuwenhoek spent fewer hours selling cloth out of the ground-floor shop in his house and more time in what today would be called his laboratory.

Leeuwenhoek was married twice, the first time to Barbara de Mey, a draper’s daughter, in 1654. They had five children, but only one, Maria, survived. She kept house for her father in later years. Daughter Barbara died in 1666, and Leeuwenhoek married a clergyman’s daughter, Cornelia van der Swalm, in 1671. Cornelia may have borne a child who failed to survive, but in 1694, she too died, leaving Leeuwenhoek with no new children.

Numerous writers have agreed that Leeuwenhoek grew interested in lenses because drapers used magnifying glasses to check the weave and to count the number of threads per inch in cloth. Yet a later researcher, Brian J. Ford, credits Leeuwenhoek’s acquaintance with Micrographia (1665), by the English scientist Robert Hooke as the inspiration for Leeuwenhoek’s move into microscopy. Leeuwenhoek apparently studied the illustrations and had sections of the book translated for him by friends.

The ingenious and meticulous Leeuwenhoek was self-taught. He seems to have done virtually everything on his own and owed little except his mathematical and drapery training to anyone else. Even his Dutch, his only language, was colloquial and nonliterary. The learned world would have paid no attention to such a man, unless his work was undeniably brilliant.

Life’s Work

Leeuwenhoek was a proper, middle-class Dutch burgher. He wore respectable clothing and a wig, had the delicate hands of a craftsperson, and possessed the keen eyesight and patience needed for detailed observation through the microscope. He was a man of presence, with a broad face and a large nose, and must have possessed an excellent constitution, for he lived to be almost ninety-one years of age.

It was apparently a Delft research physician and friend who enabled Leeuwenhoek to make connection with the Royal Society , a newly formed scientific organization in England. Leeuwenhoek had begun experimenting with microscopes in the late 1660’s, and by 1673 he had made enough startling observations that it was time for him to be discovered. He wrote his findings in lengthy, rambling letters that for the remaining fifty years of his life were regularly published in Philosophical Transactions of the Royal Society. The first selection of extracts from these letters were published by the society as A Specimen of Some Observations Made by a Microscope (1673).

Thus, the scientific world became aware of the work of the amazing Dutchman. He had not invented the microscope—indeed, microscopes had been used for at least half a century—but Leeuwenhoek’s skill at lens grinding, along with his patient and insightful mind, made him the father of modern microscopy.

In his first letter to the Royal Society, Leeuwenhoek anonymously criticized famous scientist and society member Hooke for accepting the idea of spontaneous generation of life. Leeuwenhoek had already seen that life comes from life and that maggots in meat, for example, do not simply appear but are produced from eggs laid by adult flies. He later extended his research debunking spontaneous generation by work on fleas, weevils, shellfish, and eels.

In 1680, the then secretary of the Royal Society, Hooke, proposed Leeuwenhoek for actual society membership, and he was unanimously elected. Cognizant of the honor, Leeuwenhoek remained devoted to the English organization and to no other for the rest of his life.

Leeuwenhoek’s countryman Christiaan Huygens, the greatest educated scientist whom the Netherlands produced in the seventeenth century, spent many years in France and translated many of Leeuwenhoek’s early letters into French for publication.

Hooke’s microscopic work dealt primarily with insects and plant and animal tissue, and he is mainly famous for using his low-power microscope to discern and name the cells in cork. Later, under Leeuwenhoek’s influence, he built a microscope of Leeuwenhoek’s description and did additional work. No “regular” scientist of that century—including Hooke, Huygens, and Leeuwenhoek—was both able and willing to grind the lenses and stare through them for the uncounted hours necessary to discern what was really happening in the microscopic world.

Leeuwenhoek was very accurate at estimating the relative and absolute sizes of the things he observed. The great Italian microscopist Marcello Malpighi had demonstrated in 1660 the existence of blood capillaries, but he could not see red blood cells clearly. It would be Dutch naturalist Jan Swammerdam who most likely was the first to clearly observe red blood cells through a microscope (between 1658 and 1665, although the precise date is unknown). Leeuwenhoek, however, not only gave the world’s first accurate description of red corpuscles but also correctly calculated the diameter of the red blood cell at one three-thousandth of an inch—amazingly close to the modern value. He described his findings in a 1688 letter to the society (reprinted as On the Circulation of the Blood , 1962).

The instrument Leeuwenhoek employed was the simple microscope, one with a single, beadlike lens mounted in a hole between two small metal plates riveted together. An arrangement of three screws moved the object to the proper position in front of the lens, and the entire apparatus, no bigger than the palm of one’s hand, was held to the eye for viewing. There were no tubes and no compound lenses. Hooke, with a compound lens, could achieve only a magnification of around fifty diameters, but Leeuwenhoek’s instruments have been calculated to have attained some 266 power. It has been estimated that some of his microscopes no longer in existence must have attained about 500 power magnification in order for him to have discerned the detail that he described.

Leeuwenhoek’s microscopes were so simple that he made more than five hundred of them, of which there are about nine known to be extant. Rather than disturb an interesting specimen that was properly mounted, he would often construct another microscope. His lenses were ground, never blown, and were convex on both sides. Leeuwenhoek kept his best observation technique secret, but it has been surmised from an obscure comment in one letter that he used dark field illumination for contrast. He did not employ any staining method.

Leeuwenhoek devoted much time to scrutinizing plant and animal tissue, but his best efforts were made observing microbes. He watched the movements of every kind of “animalcule,” as he termed the tiny creatures that danced, darted, floated, and vibrated under his lens. He saw protozoa, smaller organisms called bacteria, and human spermatozoa, and he studied algae, yeasts, and molds. He found these organisms everywhere—in his rain barrel, in his mouth, in nearby ponds and canals, and in the soil. He was better at verbal than at artistic description, and so he retained the services of draftsmen to produce pictures of what he saw. In this effort, it is possible that his early work was assisted by his friend and neighbor Jan Vermeer , one of the best and most precise artists of all time.

The homegrown scientist not only studied how animalcules and insects reproduced but also experimented with what would kill them. He found that pepper water would kill many microbes, that nutmeg would kill mites, and that sulfur dioxide would kill moths. He never seems to have suspected, however, that some of these tiny animals would be able to kill him. Leeuwenhoek was even visited by Herman Boerhaave of nearby Leiden University, and the august personage gravely peered through the microscopes. Professor of medicine, botany, and chemistry, and a cofellow of the Royal Society with Leeuwenhoek, Boerhaave had turned Leiden into Europe’s best-known medical center of the time. Thus, as he drew no medical conclusions from observing the animalcules, Leeuwenhoek can certainly be forgiven for not doing so. That microbes were the source of many human diseases remained virtually unknown for another two centuries.

Asking himself how microbes came to inhabit a previously sterile medium, Leeuwenhoek concluded that they were borne on the very dust motes of the air. In fact, there were few questions that Leeuwenhoek did not ask, but as a solitary and untutored investigator ahead of his time, the miracle is that Leeuwenhoek did what he did in the first place.

Significance

Leeuwenhoek is recognized as having founded the disciplines of bacteriology and protozoology. Strangely, however, he established no school of followers. He had no disciples, and he refused to train younger men to succeed him. Even though Leeuwenhoek did not train others and establish a tradition of excellent microscopy, posterity does know what he did in his half-century of research, as he wrote some two hundred lengthy and illustrated letters to the Royal Society, letters that were published in English translation. The Royal Society also received twenty-six microscopes bequeathed in Leeuwenhoek’s will—the only instruments he ever relinquished so far as is known. The society treasured them for years but eventually lost them. Luckily, the original letters were preserved.

Some of Leeuwenhoek’s best work was done when he was in his seventies and early eighties, mainly dealing with nonparasitical protozoa living in water. By that time, Leeuwenhoek was an international institution, a phenomenon to whom all paid tribute. The University of Louvain sent Leeuwenhoek a silver medal in 1716 to honor him for his work, and he was visited by numerous potentates and crowned heads of state.

Several editions of Leeuwenhoek’s collected letters appeared in Dutch and in Latin while he was still alive. He was not a man who was forgotten until he had been long dead. He had looked deeper and longer into the microscopic universe than had any other person of his time, and his world honored him. He was largely overlooked by the next several generations, until he was rediscovered in the nineteenth century, an enigmatic precursor of a science regarded as absolutely fundamental to an understanding of nature.

Bibliography

Bender, George A., and Robert A. Thom. Great Moments in Medicine: A History of Medicine in Pictures. Detroit, Mich.: Northwood Institute Press, 1966. Contains an excellent chapter on Leeuwenhoek, recounting his life and work. There is an excellent illustration of the microscopist and his workshop based on the four life portraits that were actually made of Leeuwenhoek and on other surviving artifacts and information.

De Kruif, Paul. Microbe Hunters. London: Jonathan Cape, 1926. Reprint. New York: Pocket Books, 1950. This well-written work provides a long chapter on Leeuwenhoek, whom de Kruif justifiably labels “first of the microbe hunters.” De Kruif conveys the excitement Leeuwenhoek must have felt at making humankind’s first forays into the subvisible world.

Dobell, Clifford. Antoni van Leeuwenhoek and His “Little Animals”: Being Some Account of the Father of Protozoology and Bacteriology and His Multifarious Discoveries in These Disciplines. 1932. Reprint. New York: Russell & Russell, 1958. The standard biography of Leeuwenhoek in English. Dobell, himself a microscopist and also an excellent linguist and scholar, researched old Dutch records to uncover everything that could be found on Leeuwenhoek. He quotes and comments on Leeuwenhoek’s letters and provides ample footnotes to explain sources and methods.

Ford, Brian J. Single Lens: The Story of the Simple Microscope. New York: Harper & Row, 1985. This book gives the history of the development and use of the simple microscope from the period before Leeuwenhoek’s discoveries through the nineteenth century. More than half of the book is devoted to Leeuwenhoek. The author, also a microscopist, performed research that provided him information not available in earlier publications.

Fournier, Marian. The Fabric of Life: Microscopy in the Seventeenth Century. Baltimore, Md.: Johns Hopkins University Press, 1996. Examines the work of Leeuwenhoek and four other scientists to explain the reasons for the microscope’s appearance and eventual eclipse in the seventeenth century.

Huerta, Robert D. Giants of Delft: Johannes Vermeer and the Natural Philosophers: The Parallel Search for Knowledge During the Age of Discovery. Lewisburg, Pa.: Bucknell University Press, 2003. Although this book focuses on Vermeer’s perception of the world, it describes how that perception was influenced by the microscope and other discoveries in the science of optics. Several chapters describe how Leeuwenhoek, Galileo, and other scientists created a “more optical” way of viewing the world.

Palm, L. C., and H. A. M. Snelders, eds. Antoni van Leeuwenhoek, 1632-1723: Studies on the Life and Work of the Delft Scientist Commemorating the 350th Anniversary of His Birthday. Amsterdam: Rodopi, 1982. A collection of articles exploring Leeuwenhoek’s enduring legacy and topics such as his education, his microscopes, his mechanistic worldview, and intellectual opposition to his work. Bibliography, index.

Ruestow, Edward G. The Microscope in the Dutch Republic: The Shaping of Discovery. New York: Cambridge University Press, 1996. Describes the work of Leeuwenhoek and Jan Swammerdam, discussing how their uneasiness with their social circumstances spurred their discoveries. Ruestow describes how their discoveries were both aided and impeded by some aspects of contemporary Dutch culture.

Schierbeek, Abraham. Measuring the Invisible World: The Life and Works of Antoni van Leeuwenhoek. London: Abelard-Schuman, 1959. An abridged translation of a two-volume biography written in Dutch, containing a biographical chapter written by Maria Rooseboom. Provides a good overview of Leeuwenhoek’s life and work.