But styles change, and artists move on to new explorations and techniques. Later, and elsewhere, these works would begin to look strange to a public no longer used to paintings that depicted the world this way. The look of pictures made with the camera obscura—or inspired by the insights gained from experimenting with it—began to seem unnatural in some ways. In the eighteenth century G. J. ’s Gravesande, a relative of Leeuwenhoek’s neighbor and friend Cornelis ’s Gravesande, said, of the Dutch artists’ use of the camera obscura, “The effect of the camera is striking, but false.” Perhaps this is why the baker Buyten could try to sell Monconys a Vermeer picture for six hundred guilders in 1663, but in 1813 Vermeer’s Art of Painting would be sold (as a De Hooch) for only thirty guilders.
It may be no coincidence that Vermeer was “rediscovered,” and became more widely known and wildly admired, in the mid-nineteenth century, soon after the birth of photography. In 1861 the Goncourt brothers in Paris said of Vermeer that he was “the only master who has made a living daguerreotype of the red-brick houses of that country.” Of all the Dutch painters fascinated by the new way of seeing the world in the seventeenth century, it was Vermeer who made his whole career about optical phenomena, and the way optical instruments enabled us to see the world in a thrilling new light.
PART 11
Scientific Lion
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ONE COOL SEPTEMBER morning in 1683, after taking his morning coffee, Leeuwenhoek cleaned his teeth, as he was accustomed to do every day. He rubbed his teeth and gums with salt and rinsed his mouth with water. Taking a quill pen sharpened at the end, he picked between his teeth to clean out the remains of his breakfast. He finished by vigorously wiping his teeth with a muslin cloth. At fifty-one years old, Leeuwenhoek was proud of his dental hygiene; he boasted that his teeth were so “clean and white” that “only a few people my age can compare with me.”
However, on this morning he noticed something troubling: some white matter between his teeth, looking like nothing so much as the batter his maidservant mixed up to make their Sunday cakes. He scraped some of this matter from his teeth with the quill and—as he was by now wont to do with all curious substances—reached for a flask of rainwater he had previously found to be devoid of animalcules. He mixed this with the “batter” and a little of his spittle. Putting the concoction in a little glass tube attached to one of his microscopes, he peered at it closely. “I then again and again saw,” he later reported, “to my great astonishment, that there were many very small living animalcules in the said matter, which moved very prettily.” Some had “a strong and swift motion, and shot through the water or spittle like a pike.” Others “spun around like a top.” Still other kinds “went forward so rapidly and whirled about among one another so densely” that it was like “a big swarm of gnats or flies flying about together.” Leeuwenhoek realized, with some delight, that “there are living more animals in the unclean matter on the teeth in one’s mouth than there are men in a whole Kingdom.”
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After Vermeer died, his compatriot, co-investigator into optics, and neighbor Leeuwenhoek had many milestones to come. His election as fellow of the Royal Society of London at the meeting of January 22, 1680, was one of his happiest moments. The society sent Leeuwenhoek a silver box containing a scroll announcing his appointment. Leeuwenhoek politely called it “so great but unmerited an honour and dignity.” He was proud enough that when Verkolje painted him in 1686, with the same surveying instruments portrayed in Vermeer’s The Geographer, Leeuwenhoek insisted that the certificate and silver box from the Royal Society be included as well. Once he knew he was being proposed for the fellowship, and would himself be a full-fledged fellow of the society, he stopped referring to the group as “curiuse Lieffhebbers”; now they (and he) were “geleerde Heeren Philosophen”—the learned philosophers. The great honor even caused Leeuwenhoek to adopt a new spelling of his name, leaving out the c before the k and adding a dignified “van”—becoming “Antoni van Leeuwenhoek” only in the mid-1680s. A bemused Constantijn Huygens the younger noted that the election to the Royal Society had “puffed up” Leeuwenhoek’s vanity.
The Royal Society honored Van Leeuwenhoek not only for his many discoveries but also because he exemplified the Baconian approach to science that it endorsed. Like Bacon and the fellows of the Royal Society, Van Leeuwenhoek recognized the need to make careful observations rather than leap to conclusions based on theorizing. As Leibniz would later say, after meeting Van Leeuwenhoek on a visit to Delft while traveling from Paris to Hanover in 1676, “I care more for a Leeuwenhoek, who tells me what he sees, than a Cartesian, who tells me what he thinks.” Van Leeuwenhoek pointed to his Baconian, anti-Cartesian scientific method when he told the Royal Society that it was “better served by an accurate observation than with a whole volume of Speculations, since these are nothing but brain-work.” He even exemplified the down-and-dirty aspect of Bacon’s philosophy. Bacon, England’s lord chancellor, is said to have died from pneumonia brought on by an impromptu experiment. Struck suddenly with the idea that cold might preserve meat, Bacon ordered his carriage to stop on a winter’s night so that he could jump out, buy a newly disemboweled chicken, and stuff it with snow. As John Aubrey reported, “The Snow so chilled him that he immediately fell so extremely ill, that he could not return to his Lodging … but went to the Earle of Arundel’s house at Highgate, where they put him into. . . a damp bed that had not been layn-in … which gave him such a cold that in 2 or 3 days as I remember Mr Hobbes told me, he died of Suffocation.” Whether or not it is apocryphal, the story serves to illustrate Bacon’s belief that no observation was too unimportant—or messy—to contribute to scientific knowledge. Van Leeuwenhoek followed in Bacon’s footsteps with his fearless examination of almost anything: his own blood, urine, feces, tooth plaque, pus from wounds, and the gunk between his toes after not removing his stockings for two weeks, the shavings of callouses from the feet of laborers, the wax from ladies’ ears, and lots and lots of semen. Van Leeuwenhoek’s claim that he had a weak stomach, and that strong smells and “unclean sights” made him ill, is hard to accept after reading about the smells and sights he endured for the sake of science.
His discovery and examination of the animalcules in tooth plaque embodied his Baconian approach. Van Leeuwenhoek did not rest after finding the little animals in his own mouth. He next called for two women, most likely his wife Cornelia and daughter Maria, “who, I am convinced, daily cleaned their mouths,” examining their spittle.*1 He then mixed their saliva with a little of the matter he scraped from between their teeth and discovered as many “living animalcules” as he had seen in his own plaque. And still he did not stop. He extended his examination to persons of different ages and sex whom he suspected of not cleaning their mouths as well as he and his family did.
This examination was always on his mind, so much so that when speaking with an old man, his eyes fell on his teeth which, Van Leeuwenhoek noticed, were “all coated over” with the white matter. He asked the man when he had last cleaned his teeth. The answer was that the man “had never washed his mouth in all his life.” Less dedicated natural philosophers would have ended the discussion at this point, but Van Leeuwenhoek forged ahead, asking to take a scraping of the man’s teeth. He mixed this matter with clean water. Looking at the mixture with his microscope, Van Leeuwenhoek reported, “I observed an incredible number of living animalcules, swimming more nimbly than I had ever seen up to that time.” He was not surprised to learn that the old man had several rotting teeth.
In one final experiment, Van Leeuwenhoek checked the white stuff scraped from his own teeth after drinking coffee “so hot that it put me in a sweat.” He found many fewer moving animalcules and concluded that, “being unable to bear the heat of the Coffee, [the animalcules] are killed by it.” He found that adding vinegar to the water solution containing animalcules also caused them to stop moving.
By this careful, empirical method, Van Leeuwenhoek had
discovered tiny living creatures in the mouth. He inferred that they caused what was called “stenching [stinking] breath.” He suggested, but did not definitively conclude, that these animalcules could lead to tooth decay, as in the mouth of the old man who never cleaned his teeth. Van Leeuwenhoek found that they could be killed by hot liquids or by frequent rubbing of the teeth with salt and vinegar. Presumably he mentioned these conclusions to his friends in Delft. If so, they might have been spared an epidemic that was ravaging the teeth of many citizens in the Dutch Republic: a craving for sweets, fueled by the new availability of sugar from Brazil.
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As Van Leeuwenhoek’s fame grew, he was visited by more and more people passing through Delft—so many that sometimes he had to instruct his daughter to tell callers he was not at home. He could not receive everyone, or else (as he put it) he “would have no freedom, and would be like a slave.” By this point, Van Leeuwenhoek required that his visitors bring letters of introduction from someone he knew. Even so, in the space of four days in 1711, he received twenty-six people, all of whom had the requisite letters, except for a duke, a count, and their tutor (whom he let in anyway). In 1680 Constantijn Huygens the younger wrote to his brother Christiaan, “Tout le monde court encore chez Leeuwenhoek comme le grande homme du siècle!” (The whole world still comes to pay homage to Leeuwenhoek as the great man of the century!)
Though he grumbled about the interruptions, Van Leeuwenhoek could not resist showing his observations to others, especially when scientific luminaries—and members of royal families—came knocking on his door. He prepared special microscopes with specimens already attached to them, so that he was ready to show them to visitors. He proudly announced that he had revealed to James, the Duke of York (the future James II of England), the sperm of a dog in October 1679. Van Leeuwenhoek reported, “His Highness admitted that he not only saw that they lived, but that he even could clearly distinguish their tails.” Years later, he would recall also showing the future king the leg of a louse. The duke had been forced by his brother, King Charles II, to go into exile after an “Exclusion Bill” was put forward in Parliament to keep James from inheriting the throne because of his conversion to Roman Catholicism. In 1679 James had been living at The Hague with his daughter and son-in-law, the stadtholder Prince William of Orange; he left for Brussels soon after seeing Van Leeuwenhoek, and returned to England in 1680. On the death of his brother, in 1685, the Duke of York did inherit the throne, becoming James II, but he was soon deposed in the “Glorious Revolution”—by none other than his son-in-law, who, becoming William III, ruled with James’s daughter Mary.
Mary herself had come to visit, soon before leaving The Hague for England. She had arrived unannounced, and Van Leeuwenhoek was not in Delft, to his everlasting regret. But he was home when Peter the Great, czar of Russia, arrived in 1698. The czar had the eccentric habit of talking to sailors who would dock in St. Petersburg, and by doing so he had learned enough Dutch that when he visited England, Gilbert Burnet, the bishop of Salisbury, was deputed to use his knowledge of Dutch to communicate to him “such information of our religion and constitution as he was willing to receive.” The czar, who displayed a keen interest in science, could also converse with Van Leeuwenhoek in his own language. One of Van Leeuwenhoek’s friends later reported that when the czar left The Hague in a canal yacht, and passed by Delft, he sent two men to ask Van Leeuwenhoek to come meet him on his boat. The czar wanted especially to see Van Leeuwenhoek’s “incomparable magnifying-glasses.” Van Leeuwenhoek spent two hours on the boat, showing the czar many of his remarkable discoveries. The czar was most struck by “the marvelous circulation in the tail of an eel.” He delightedly watched this sight again and again. At the end of their time together, the czar “shook Leeuwenhoek by the hand, and assured him of his special gratitude for letting him see such extreme small objects.” (On a later visit to the Dutch Republic, in 1717, the czar toured the hortus botanicus with Boerhaave in Leiden and purchased Ruysch’s celebrated and creepy cabinet for thirty thousand guilders, or over $2 million today—a cabinet that included Ruysch’s preserved “little children … whom he has carefully preserved … so that they seem to be sleeping.”)
Van Leeuwenhoek was particularly excited about showing visitors what he considered the most exciting spectacle of his entire career, the circulation of blood in the capillaries of tadpoles. By setting up a special tube behind the lens, in which he could place and hold the tail of a living tadpole, Van Leeuwenhoek observed the propulsion of the blood globules through the capillaries—some of which were so narrow that only one corpuscle at a time could pass through—and determined that this circulation was synchronized to the heartbeat of the animal. This led him to realize that the capillaries constituted the final link between arteries and veins in the circulatory system. He began inviting various gentlemen to come and see this new spectacle for themselves. It was such a “beautiful sight,” he believed, it should be shared with others. He was moved to publish two different designs of the special “aquatic microscope” he had designed for these observations, showing the frame that held a small tube into which the tail of the tadpole or a baby eel could be placed (he still neglected, however, to give any specifications for the lens used). But such viewings were also a way to remove doubt about what he saw, to allow others to confirm his observations without reproducing the experiments for themselves. Inviting observers, Van Leeuwenhoek admitted, was the best way to ensure that he “might suffer less contradiction.”
Van Leeuwenhoek continued his observations, using the methods of investigation he had developed decades earlier. After first seeing sperm in 1677, he returned again and again to the sperm of different animals, still looking for the little creature inside. He discovered the banded pattern of muscle fibers in 1682. In the 1680s and 1690s he engaged in a series of microdissections of insects, studying the mouth and sting of bees and discovering that aphids reproduce by parthenogenesis, asexual reproduction: female aphids are born containing babies within. In 1684 Van Leeuwenheok discovered the needle-shaped microscopic crystals of sodium urate that form in the tissue of gout patients, correctly inferring that the sharp, needlelike structure of the crystals is what causes the pain of the disease. He was the first to observe the microorganisms Vorticella and Stentor, as well as diatoms and sessile rotifers.
And he remained obsessed with vision. In 1713, when Van Leeuwenhoek was eighty-one, he persuaded the captain of a Greenland whaling ship to bring him back an enormous eye of a whale, which had been preserved in brandy. (He also requested, and received, the whale’s penis, similarly preserved.) Van Leeuwenhoek cut sections of the cornea, trying to determine the number of layers in it. He thought it was made up of sixteen to eighteen thin layers, but found the sclerotic layer of the eye—the hard fibrous membrane that makes up the topmost layer of the eye, of which the cornea is the outermost part—very tough, and almost impossible to section, although he was using a very sharp knife.
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Even today we must marvel at the discoveries made by Van Leeuwenhoek, and wonder how he could be so successful at observing microscopic organisms and structures with his single-lens instruments. He was constructing microscopes with excellent lenses, to be sure, but by the time his career was well under way microscopes equaling the magnification and resolution of his average instruments were readily available, for sale in England by the firm of Edward Culpepper and in the Netherlands by the Van Musschenbroek family. So there was more to Van Leeuwenhoek’s success than just the quality of the microscopes he made. Could it have been the method of observing that he used?
Since Van Leeuwenhoek never revealed the exact methods he employed, we must speculate about them, just as we must speculate about the methods Rembrandt used to make his etchings so special and the optical experiments made by Vermeer. But we do have enough information to make some reasonable inferences.
In some of his early letters Van Leeuwenhoek revealed that he had been observing in his da
rk study. There were four windows in the room, which could be closed by two wooden shutters, one on each side. Sometimes he left a small opening in one shutter so that he could aim his microscope into the beam of light, like looking at the sky with a telescope, as he described it. But at times he used a different method. He would close the shutters completely, opening a little casement window above them if his lit candle began to bother him with its soot. Even then, he was careful to draw a curtain over the opened window. He explained that he shut up his window shutters to keep out the air so that any animalcules floating in it could not contaminate his water sample. But this setup may also have proved decisive for his discoveries.
Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing Page 33