Antony van Leeuwenhoek1,2 (1632–1723), is famous as the discoverer of the single-celled microorganisms we now call protozoa and bacteria. He called them ‘animalcules’.3 He also was the first to accurately measure red and white blood cells, spermatozoa, nerve and muscle fibres, and much, much more. He believed that the perfection he observed in such tiny organisms was due to their being created by God.
Encyclopaedia Britannica acknowledges: “His researches on lower animals refuted the doctrine of spontaneous generation, and his observations helped lay the foundations for the sciences of bacteriology and protozoology.”4 He never attended a university, wrote a book, or gave a lecture, but described his discoveries in letters to the Royal Society of London, which published them in its journal, Philosophical Transactions of the Royal Society.
Antony was born in Delft, then the third-largest city in the Dutch Republic,5 and is now in South Holland, the largest and most populated province of the Netherlands. His schooling did not involve any language other than the local Nether-Dutch, spoken in South Holland, so he did not learn Latin, the scientific language of that day. Everything that he wrote was in Dutch, which meant that recipients such as the Royal Society had to translate his letters into English (or occasionally into Latin) for publication, and someone translated their replies into Dutch for him.
In 1648, at the age of 16, he was sent to Amsterdam to learn the drapery trade. He worked there for Scottish textile merchant William Davidson, becoming his cashier and accountant. In 1654, he returned to Delft, where he set up a drapery and haberdashery business and married Barbara de Mey, the daughter of a local textile merchant. They produced five children, although sadly only their second daughter, Maria, survived early infancy.6
He then lived in Delft for almost 70 years and was appointed to several municipal positions. One of these was Trustee for the estate of fellow-Delft artist Johannes Vermeer, who was born in the same year as Leeuwenhoek, but died in 1675 leaving a widow, 11 children, huge debts, and some of the world’s best paintings.
In or about 1668, he holidayed in London.7 Here, he undoubtedly saw English scientist Robert Hooke’s newly published and ‘best-selling’ book, Micrographia,8 which documented Hooke’s microscopic observations of many familiar objects. These included some high magnifications of woven silk fabric, which would have intrigued draper Leeuwenhoek; it also contained “the first published illustration of a microfungus”.9
Hooke’s book may well have stimulated Leeuwenhoek’s interest in lenses into the consuming passion it became. This involved his making his own high-magnification lenses, mounting them to form simple microscopes (see box), and then examining and measuring10 a host of miniscule objects in response to his growing insatiable curiosity regarding things imperceptible to the naked eye.
One of Leeuwenhoek’s friends in Delft was a physician, Dr Regnerus de Graaf. On April 28, 1673, de Graaf wrote to Henry Oldenburg, the first Secretary of the Royal Society in London and founding editor of its Philosophical Transactions: “I am writing to tell you that a certain most ingenious person resident here, named Leeuwenhoeck [sic], has devised microscopes which far surpass those we have hitherto seen. …”11 He enclosed a letter from Leeuwenhoek describing the latter’s observations on the structure and growth of mould; on the sting, limbs, and eye of a bee; and on the head, feelers, and legs of a louse, which Oldenburg published (English’d) in the Philosophical Transactions.12 Intrigued, readers wanted to see what was described, so on August 15, 1673, Leeuwenhoek sent the relevant illustrations,13 with a note to say that because he couldn’t draw well, he had employed a draughtsman who had observed each object through a different lens.
Thus began a correspondence of some 200 letters from Leeuwenhoek to the Royal Society that continued for fifty years “on matters zoological, botanical, chemical, physical, physiological, medical, and miscellaneous (unclassifiable) … all written by himself in his own old-fashioned Dutch, though they were often translated by others into other languages, published in many different ways, and collected in various volumes at divers dates by different editors.”14 Henry Oldenberg, in fact, learned Dutch in order to translate Leeuwenhoek’s letters for himself.
Leeuwenhoek was particularly interested in blood. To observe and measure blood cells (discovered by Italian scientist Marcello Malpighi in 1665), he pricked his thumb and smeared the blood on a small glass tube. In his letter of 1 June 1674, he wrote: “The red globules of the blood I reckon to be 25,000 times smaller than a fine grain of sand.”15 This equates to about 8.5 microns, which is close to the modern measurement of ~7–8 microns.
In 1674, Leeuwenhoek examined some water from a freshwater lake called Berkelse Mere near Delft. In this, he saw some organisms that were manifestly protozoans, as described by him briefly in his letter to Henry Oldenburg:
“And the motion of most of these animalcules in the water was so swift, and so various, upwards, downwards, and round about, that ’twas wonderful to see: and I judge that some of these little creatures were above a thousand times smaller than the smallest ones I have ever yet seen, upon the rind of cheese, in wheaten flour, mould, and the like.”16
Then in 1676, Leeuwenhoek wrote the now-famous 17½-page letter in which he described sighting bacteria, part of which Oldenburg published in the Philosophical Transactions 12(133):821–831, 1677. In it, he related what he saw on 24 April 1676, in water in which he had soaked pepper for about three weeks and to which he had twice added snow-water (the purest water available) to replace that which had evaporated away. He described three types of what we now call protozoa and then wrote:
“The fourth sort of little animals, which drifted among the three sorts aforesaid, were incredibly small; nay, so small in my sight, that I judged that even if 100 of these wee animals lay stretched out one against another, they could not reach the length of a grain of coarse sand; and if this be true, then ten hundred thousand [i.e. 100 × 100 × 100 = 1 million] of these living creatures could scarce equal the bulk of a coarse sand-grain.”17
Biologist Prof. D. Bardell commented: “An organism that is incredibly small compared with a protozoan is the reason for belief that van Leeuwenhoek discovered bacteria on 24 April 1676.”18
And Dutch microbiologist Prof. Albert Kluyver said: “The measures given leave no doubt that he observed bacteria here; consequently this is the first unmistakable description of representatives of this group of organisms, and there is every reason to consider the 24th April, 1676, as the birthday of Bacteriology.”19
In a further experiment with pepper-water, Leeuwenhoek described seeing “some very long and very thin particles … [that] moved with bendings, as an eel swims in the water; only with this difference, that whereas an eel always swims with its head in front, and never tail first, yet these animalcules swam as well backwards as forwards, though their motion was very slow.”20 Protozoologist Clifford Dobell commented: “A remarkably shrewd observation, which proves conclusively that L. was here dealing with bacteria. The organisms were evidently the long flexible thread-bacteria (Pseudospira C.D.) so common in infusions.”21
Later, Leeuwenhoek was astonished to find in scrapings from his teeth, “many very little living animalcules, very prettily a-moving”. Thus he discovered that we too are carriers of animalcules, which he also noted died when he drank hot coffee.22 So he was the first to observe that microbes are killed by heat. Because he discovered bacteria in the mouths of healthy people, including himself, it is understandable that he did not associate bacteria with disease, as we often do today. But most bacteria are harmless, just as he thought, and many are even beneficial, e.g. probiotics, and thus protected by our appendix. It wasn’t until 1860–64 that Louis Pasteur proved the germ theory of disease, and then devised pasteurization to destroy harmful bacteria, and further developed vaccination to train our immune system to combat them.
The Fellows of the Royal Society were hugely skeptical, and understandably so, as Leeuwenhoek, a layman, was describing phenomena that not one of these scientific intelligentsia had ever seen, much less looked for, or even imagined existed. Challenged, Leeuwenhoek assembled eight Delft gentlemen of repute, including a Lutheran minister, a notary, and a barrister, who peered through his microscopes, saw the animalcules, and wrote affidavits, which he then sent to the Royal Society by letter dated 5 October 1677.
Meanwhile, the Fellows had asked Hooke, who was their Curator of Experiments, to verify the observations. For several months he tried unsuccessfully, until finally, in November 1677, he was able to demonstrate the animalcules, and wrote: “ … much to wonder I discovered vast multitudes of those exceeding small creatures, which Mr Leeuwenhoek had described … and some of these so exceeding small, that millions of millions might be contained in one drop of water”.23 Hooke wrote a courtesy letter to Leeuwenhoek, dated 1 December 1677, in which he said “all the members present were satisfied”, and he contrasted the size of the tiny protozoa with that of the much smaller bacteria as “gygantick monsters in comparison of a lesser sort”.24
Confirmation! And reward! In 1680, Leeuwenhoek won recognition as a true scientist by being elected a Fellow of the Royal Society. His membership certificate was worded for his benefit in Dutch instead of the usual Latin.25
Membership of the Royal Society and publication of his letters in the Philosophical Transactions made Leeuwenhoek and his work famous all over the world. Not only scientists, but crowned heads too came to Delft to see him and peer through his microscopes. These included Tsar Peter the Great of Russia, King Frederick I of Prussia, the future King James II of England, and his daughter, the future Queen Mary II of England, to whom he presented two of his silver microscopes.
People of Leeuwenhoek’s day who disregarded Genesis believed in the Aristotelian theory of spontaneous generation,26 e.g. that decaying meat produced maggots, dust produced fleas, wheat kept in a dark corner turned into mice, etc. As a Bible-believing Christian, Leeuwenhoek rejected spontaneous generation and repeatedly stated that the perfections he saw in his tiny organisms were created by God and were not the product of corruption. Some examples:
“We cannot in any better manner, glorify the Lord and Creator of the Universe, than that, in all things, however small soever they appear to our naked eyes, but which yet have received the gift of life, and power of increase, we contemplate the display of his Omniscience and Perfections with the utmost admiration.”27
“… as it is impossible for an elephant to be brought forth from dust or dirt, it is equally impossible for a Mite to be bred out of meal or any corrupted substance, or in any other manner than the regular way of generation I have described.”28
“From all these observations, most plainly we discern the incomprehensible perfection, the exact order, and the inscrutable providential care with which the most wise Creator and Lord of the Universe has formed the bodies of these Animalcules, which are so minute as to escape our sight, to the end that the different species of them may be preserved in existence. And this … must surely convince all of the absurdity of those old opinions, that living creatures can be produced from corruption or putrefaction.”29
Also his observation of the life cycles of insects (from eggs to larvae, to pupae, to adults which then laid eggs or produced live young), showed that they came from parents like themselves,30 and not from manure. And he saw this as a “confirmation of the principle that all living creatures derive their origin from those which were formed at the Beginning.”31
Today, spontaneous generation (the belief that a living thing can arise from non-living matter) is euphemistically called chemical evolution or abiogenesis,32 and is once again the dominant belief system of atheistic scientists. It is a natural and crucial predecessor of Darwinism; if all life evolved ‘naturally’ from a single-celled common ancestor, they reason, that itself must have also arisen from dead matter unaided.33 Proponents search the earth, the solar system, and the universe relentlessly, striving to find evidence of it so as to deny the creation account in Genesis.
Leuwenhoek enjoyed excellent health for most of his life. He died on 26 August 1723, aged 90. He had sent the Royal Society such a detailed, first-ever description of the medical condition that caused his death that it is now called van Leeuwenhoek’s Disease! This very rare condition involves episodes of rapid involuntary contractions of the diaphragm, or diaphragmatic flutter, causing shortness of breath, rapid breathing and abdominal pulsations, so it is also known as Belly Dancer Syndrome.34
Although only a layman, Leeuwenhoek was one of the most outstanding researchers of all time, with an insatiable curiosity to discover the hidden secrets of nature. A major scientific concern was to refute the theory of spontaneous generation. His self-confessed purpose: “… in order to draw the World away from its Old-Heathenish superstition, to go over to the Truth, and to cleave to it.”35
“In his faith Leeuwenhoek was solidly Dutch Reformed. He often referred with reverence to the wonders God designed in making creatures small and great. His virtues were perseverance, simplicity, and stubbornness. He loved truth above any theory, even his own. He asked of his challengers only that they prove their points as he proved his.”36
Leeuwenhoek’s microscopes consisted of single lenses, which he made himself—over 500 of them—quite possibly one for each specimen that he examined over 50 years.
He was very secretive about how he made them—whether by grinding and polishing a piece of glass with increasingly fine grit, or by blowing a tube of hot glass to form a blob, or by drawing out a hot glass thread in a flame until it broke and then heating the end of one thread till it melted and formed a tiny globule.37 Or he could have used a combination of these techniques, as “all his lenses were biconvex or planoconvex”.38 All were of remarkable clarity.
He mounted each lens in a tiny hole between two thin metal plates riveted together that he made out of brass, silver or very occasionally gold,39 with the specimen in front of the lens on a sharp point that could be focused by two screws.40 The largest surviving plate measures 28 × 47 mm. The smaller the lens, the greater the magnification, but also the smaller the field of view, so the reverse side needed to be held very close to one eye for viewing because of the very short focus, and this required great patience on the part of the user.
His light source was a candle or the daylight, but not the sun, as he explained to his Royal Society readers: “I contemplate in a clear day, and sometimes by Candlelight, and to have still more light, I use sometimes a metal Concave Looking glass, but above all things you must have a care, not to make your view in the Sunshine, for if you do so, the Circumference of each Animal, will have almost as many Colours, as we see in the Rainbow.”41
Encylopaedia Britannica adds: “In order to observe phenomena as small as bacteria, he must have employed some form of oblique illumination, or other technique, for enhancing the effectiveness of the lens, but this method he would not reveal.”42
After his death, his daughter, Maria, sent to the Royal Society a small cabinet containing 26 silver microscopes, with specimens still attached, which Leeuwenhoek had prepared for this purpose. Magnifications of these varied from 50× to 200×.43 In 1747, after Maria’s death, 517 instruments were put up for public auction.44 Of all the above, only 12 are reckoned to still exist.45 In 2009, Christie’s in London auctioned one; it sold for £260,000. The best is in the Utrecht University Museum. Its plate measures 24 mm × 46 mm, and it has a linear magnifying power of 266× and a measured resolution of 1.35µ.46 However, from Leeuwenhoek’s recorded observations, it is generally reckoned that he must have made some lenses that magnified 500×, with a resolution of 1.0µ.
In 1981, researcher Brian Ford discovered in the Royal Society archives nine packets of original samples sent by Leeuwenhoek in 1674, 1686, and 1687. Unopened for 300 years, “they were as well prepared as many modern specimens.”47