First microscope
First reaction
Old microscopes
Category History of Science. Microbiology & Cellbiology. Copyright © 2003 Warnar Moll.
[Down Spanish]


All science begins with astonishment (PLATO), but the human behind the instrument is much more important than the instrument itself.

SCIENTIFIC Life and Misconceptions
QUALITY of the Simple Microscope
"BLOODLESS ANIMALS" and the plague.
MISSIVES Leeuwenhoek´s letters
Leeuwenhoek and the TEA-Doctor C.Bontekoe
The last missives
The year 1632
CLICK HERE for other portraits of van Leeuwenhoek

Antonius Leeuwenhoekius Delphis Natus MDCXXXII

  Ant, life stadia, "Mier"
Bacteria (1683) in tooth plaque, human skin and gut
Bird´s feather and hair of a pig
Blood corpuscles,(Erythrocytes,circulatory system,nucleus,brains)
Braintissue of the pig
Capricorn beetle
Centiped from East India, the Stinging Nettle and "Vlijm"
Christian Huygens. A hypothesis about the Earth-Movement
Coffee bean and germ
Corn weevil ("Klander")
Cottonseed and plastids
Cottonseeds and More seeds
Crystals in Vinegar,the "Wine-eel",Calcium-carbonate
Curare, salt crystalls
Generatio Spontane: Aristotle, Leeuwenhoek and Pasteur
Globules in leaves (Chloroplasts)
Insects in Amber
Libellulidae, Damselflies, "Lampoons"
MICROSCOPE: Zaccharias Janssen Microscope tube (design 1595)
MICROSCOPE: Leeuwenhoek´s Simple Microscope (design 1670)
MICROSCOPE: Leeuwenhoek microscope engraving by Henry Baker (1756)
MICROSCOPE: John Cuff´s double compound Microscope (± 1750)
MICROSCOPE: Studying bloodcirculation in the Eel (Fishglass, design 1688)
MICROSCOPE: Adapted for use with the Camera Obscura (1871)
MICROSCOPE: Carl Zeiss Jena, Compound Microscope (Designs 1878,1930,2002)
MICROSCOPE: Rudolf Winkel, Göttingen
, Monocular microscope (Design 1885)
Missive of G. Bidloo to van Leeuwenhoek ("Fluke")
Missive 59 to Boerhave about the male semen
Missive 65 to Swammerdam and Harvey
Mosquito (Culex), stinging parts,larva and Snout-beetles
Muscle fibers
Mussel, Molluscae (filter system)
Nerves of the spinal chord (Lamb)
Nutmeg (Myristica fragrans),Missive 88, "Noote-muskaat"
Plant louse on the Ribes red-currant
Poem on the titleplate by Thomas vander Wilt
Portrait of van Leeuwenhoek
Pulex irritans, flea,"vlo"
Quasi Experimental Approach: Null-hypothesis about Anaerobic life ?
Silk-worm and cocoon
Size estimation of Infusoria
"Smallest fly"
Spermatozoids ("swimming in the uterus of a Rabbit")
Tadpole - Frog metamorphosis, "kikkervisje"
Titleplates (a) Romyn De Hooghe, (b) J.Goeree, (c)  van Schaak
Van leeuwenhoek´s family doctor
Van Leeuwenhoek´s last observations
Vascular system in the wing of a night-moth
Vitreous-body of a Codfish eye and crystalline-body
Wheat germ, "Tarwekiem"
Wood structure and Annual rings
Yeast ("Wax-model"-globules,"gist")

Van Leeuwenhoek´s scientific life



The purpose of this essay is, throwing light on some of van Leeuwenhoeks´s less well-known experiments and observations and to provide a short outline of the life and times of "the father of microbiology and cellbiology" Antonie van Leeuwenhoek. A selection from the original etchings has been made and is presented on this site.
The information on this web-document is far from being complete. Exhaustive documentation and sources about Antonie van Leeuwenhoek and his works are available both in literature as well as on the web: see REFERENCES, [REF:UBA 70,73].
Further, it is mentioned that the Dutchman Jan Cornelis Mol (a microcinematographic artist, 1891 Venhuizen -1954 Heemstede, son of Cornelis Mol and Maartje Nobel) together with W.H. van Seters already produced a prestigious scientific film about Antonie van Leeuwenhoek in 1924, and in which they used a new technique to observe the bloodcirculation, living micro-organisms and crystallization of potassium- and other materials [REF: 81]. In 1930 the well-known Dutch cineist Joris Ivens presented this film on an exposition at Stuttgart (Germany).

Religion and Science

Throughout the centuries, discoveries have been made either to the honour and glory of God,to enhance military power, to the benefit of trade or both. Most of the scientists who laid the basis for the scientific age, including Boyle, Copernicus, Galileo, Keppler, van Leeuwenhoek, Huygens and Newton, believed in a personal God who revealed Himself in the Scriptures and answered prayer.

In many cases however, discoveries were neglected, denied or even put a ban upon them by the clergy. In the year 399 A.D., Socrates (born ± 470 B.C.) was charged by three fellow citizens of corrupting the minds of the youth, and of worshiping gods other than those of the city of Athens. He was judged guilty and sentenced to death by hemlock. Galilei Gallileo was summoned to Rome in 1633, being vehemently suspected of heresy and he had to abjure the principles of Copernicus, kneeling in front of members of the Inquisition.
At the onset of the Reformation, the Spaniard Michael Servetus (1509 or 1511-1553), theologian and the discovery of the Lung-blood-circulatory system is attributed to him, was one of the first Martyrs (De Trinitatis erroribus) because of his standing against the Trinity doctrine, formulated by Q.Tertullianus (155- ± 230 ? AD) [REF: 78]. Servetus was betrayed by John Calvin (1509-1564) to the Catholic Inquisition [REF: 65, 66] and he was burned on the morning of October 27, 1553. In words of Calvin himself : "I really do hope that Servetus will be sentenced to death, at least: Let the judges be as cruel as possible !"

Though, Renaissance could not stop the development of new scientific ideas. Dogmatic principles could not check anymore the progress of scientific curiosity in the minds of human beings. Interestingly enough this should remind us to the situation in the prosperous Islamitic world of the past : Already Islamitic philosophers (Avicenna, Hunayn ibn Ishaq, Rhazes) and the physician and philosopher Ibn an Nafis (1210-1288 AD) in Damascus, succeeded in finding that the lungcirculation was a closed system (see the images below).

Canon Medicinae, Avicenna or Ibn Sina (990-1037) and descriptions of lungs,heart,brains and liver.

Human bloodcirculation, ± 1420.

So let us keep in mind that the early Arabic scientists were the direct pioneers of the European Renaissance. And it were many of them who brought to us the findings of the ancient Greeks (Aristotle, Plato and Galenus) in a time that religious dogma´s and scientific interpretations were absolutely independant from each other [REF:67].

In Western Europe the Scientific Revolution (1450-1750) [REF: 86] almost parallels the Renaissance. In particular the XVIIth century was the Age of Reason, a time of absolute monarchy, and the Age of Enligtenment. As the Renaissance flourished (from Macchiavelli and Leonardo Da Vinci,-Italy-, Newton - up to Huygens and van Leeuwenhoek in the Netherlands-) the scientific way of thinking changed drastically and influenced worldhistory profoundly. People of all social layers became more curious than ever before and started to ask independant questions [REF: 59] that could not (and would not) be answered by religious authorities [REF: 59, 60, 61]. According to Thomas Kuhn (1922-1996)[REF:74] the pre-paradigmatic phase of the natural sciences ended during Renaissance. In the XVIIth century, Antoni van Leeuwenhoek, the last amateur-scientist of the Renaissance, peered through a simple construction of lenses and screws and observed "animalcules" dancing through a drop of water [Animalcules: tiny beasties living all around us]. This was the first step toward recognition that microbes were the cause of infectious disease. Ever since this discovery, humankind has been fascinated with the microscopic world. To day,given once a decade by the Science Division of the Royal Netherlands Academy of Arts and Sciences [REF:56], a prestigious Leeuwenhoek Medal is awarded for outstanding contributions to the study of microbiology.

Discoveries and dissections ("Ontdekkingen en Ontledingen")

It is a general belief that Leeuwenhoek´s first 27 letters are either lost or unpublished. Nevertheless, this is a misconception. The truth is that most of these first 27 letters are still extant in manuscript and many of them have already been published in the early volumes of the Philosophical Transactions of the Royal Society. These letters are written in Leeuwenhoeks´s own hand [REF:75]. See figure below : letter 3a, Delft in Holland, 16 april 1674, to Henry Oldenburgh :

First letter Leeuwenhoek
See also unpublished letter nr. 16, 1676:Woodstructure [click]


The main discoveries of Antonie van Leeuwenhoek are: red bloodcells (1673), infusoria (1675), spermatozoa (1677) and bacteria (1683).

Since van Leeuwenhoek´s discoveries, we humans realized that our world is teeming with science-fictionlike tiny little monsters beyond our eyesight. Referring to Antonie van Leeuwenhoek as the first human being observing life through the microscope is a historical fact, though saying he was the inventor of this "magnifying glass" is a misconception. Probably, one of the first who abusively mentioned van Leeuwenhoek as the "inventor of the microscope" was the Dutch political leader and historian mr. G. Groen van Prinsterer in 1852 [REF:38]. Brought up to business van Leeuwenhoek started as a merchant. Experts disagree when he became interested in microscopy. In this field he was "the untrained layman" and was not a teacher (see hereafter, Short Biography). In some biographies van Leeuwenhoek is described as "the janitor from Delft" but the term "janitor" is misleading. In Delft he was the owner of a fancy-wool shop and certainly used magnifying glasses to investigate the quality of textile. Further,he was a wine assayer, a city official and a surveyor in Delft. Antonie van Leeuwenhoek received only an elementary education and spoke only Dutch. However,in his works he frequently used official medical terms in latin. From his works it can be concluded that van Leeuwenhoek was acquaint himself with the scientific theories of his contemperaries (for instance: Hooke, Newton, Leibnitz, Boerhave, Huygens, Stevin, Harvey, Swammerdam). Though not being a professional scientist in the true meaning, his discoveries were not at all neglected as were suggested by some. On the contrary, the famous Herman Boerhave (1668-1738) himself mentioned van Leeuwenhoeks observations about the muscles and the semen in his works (see also Missive to Boerhave). These (posthume) works were translated in all European languages including Arabic.

BOERHAVE about van LEEUWENHOEK´s observations (Posthume edition by Johannes Grysius, 1745:SPIEREN-MUSCLES, MANNELYKEZAADS-SEMEN)

Unable to read English, van Leeuwenhoek was known to consult translators when he needed them [REF:4].On the otherhand, he was not very enthousiastic letting to translate parts of his work into latin.
Van Leeuwenhoek never published his method of how to grind his superb lenses, he used several microscopes of different quality and he used some method to improve the quality of his preparations saying :"Die ik alleen voor myfelf houde" [= "which I only keep for myself"]. By keeping his methods secret he remained throughout his long lifetime the sole occupant of the field he had created.

Antonie van Leeuwenhoek discovered organisms we now know to be single-celled, but Robert Hooke (1635-1703) was the first who described a cell. Van Leeuwenhoek observed the swarming of his animalcules but failed to observe their division. However the assertion that he could only reinforce the idea that they arose spontaneously [REF:51] is a misconception as will be pointed out here-after.

In 1839, nearley two centuries after this discovery cells were finally ackowledged as the ubiquitous units of life by the Germans Matthias Jacob Schleiden (1804-1881) and Theodor Swannn (1810-1882).


Aristotle was the first to introduce the term bloodless animals : the two major
categories in animal kingdom were blooded animals (red blood only) and bloodless animals.

Just about a few decades after the decease of van Leeuwenhoek (1723) an interesting case was published by Izaak van der Vinne in 1745, about an epidemic (diarrhoea) in the city of Kampen (The Netherlands) during the year 1736. In this rare book, Evert Valk, a physician, declared:

"Een geneeskundig verhaal van de algemeene loop-ziekte, die te Kampen en in de om-geleegene streeken heeft gewoed in 't jaar 1736 neevens een werktuigkunstige, en natuurkundige beschryvinge van de oorzaak, uitwerking en genezinge waar in word aan-getoond, dat dezelve, waarschynlyk, door bloed-loose diertjes, beschreven in de werken van Anthony van Leeuwenhoek, het werd te weeg gebragt, en door kwik voor-naamentlyk, uit-geroeid."


"A work on a disease in the city of Kampen (1736, The Netherlands ) which originated (caused) by " little animals". These ' bloedloze dieren' (bloodless animals, the Invertebrata) are- most likely- the little animals described in the work of Leeuwenhoek and they could be killed by treatment of mercury (quicksilver)."

Indeed, in this publication " GENEES KUNDIG VERHAAL VAN DE ALGEMENE IN ZWANG GEGAAN HEBBENDE LOOP-ZIEKTE...", the author uses the work of Leeuwenhoek in describing the disease, draws some (preliminary) conclusions about the cause of the disease, he warns "non-believers of van Leeuwenhoek to use a magnifying glass" and gives commentaries on the work of Anthonie van Leeuwenhoek and his findings. See image below:

In this work, Valk says that "he is convinced that the plague is also transmitted by the little animals already observed by van Leeuwenhoek and that these "little bloodless animals" can be found in dirty clothes, wool-sacks or hemp and thus can be transported from one country to the other, traveling on trade routes", not yet being conscious of the crucial role of the flea. [The bubonic and septicemic plague (black death,Yersinia pestis) is transmitted by the bite of a flea infected by these "little animals". Fleas, humans, and rats serve as hosts for the disease.]


Antonie van leeuwenhoek had a sanitary attitude, warned about filthy water in the city-canals and probably disliked smoking:
In a missive to Antonius Heinsius (Missive 106, 1696), van Leeuwenhoek declared that ("in trying to keep down his tooth-ache") he had become so ill by smoking a pipe that he could not stand anybody talking to him:

"Siekte door het tabacq rooken : Eer dat ick den pyp met tabacq half uitgerookt hadde was ick foo fiek .... ja foodanig dat ick niet konde verdraagen dat men my aansprak...."

In the same letter van leeuwenhoek described the immediate serious allergic reaction of a man after eating Salmon or any other fish ("sweatiness and his neck became red like blood").


The Impact

An analysis of the history of technology shows that technological change is exponential, contrary to the common-sense "intuitive linear" view. However, it lasted almost 200 years until the findings of van Leeuwenhoek could be improved with more sophisticated instruments.

Antonie van Leeuwenhoek, who lived in a time of discoveries without advanced chemistry, medical science or sophisticated technology, was an accurate observer. He tried to interprete his observations, without being dependant on the limited or erroneous ideas of his contemporaries, whether they were prominent scientists or common people. And he did not feel ashamed to study delicate matters such as the principles of reproduction.

He sometimes investigated objects in behalf of other scientists who could not study or publish their findings because,"they live in less liberal countries" (according to van Leeuwenhoek himself).

The discoveries made by van Leeuwenhoek did not end the believe in the Spontaneous Generation Theory : To some scientists (Needham 1745) it only served to enhance their believe in the Spontaneous Generation Theory [REF:48]-[REF:42].
The discovery of microorganisms by Antonie van Leeuwenhoek led some to speculate that these organisms might be the cause of disease, but the germ-theory of disease was developed by Robert Koch [REF:40] in the 1870´s while studying Bacillus anthrax.

Already from the very first moment Antonie van Leeuwenhoek sent his letters to the Royal Society in London, numerous articles are published since about Antonie van Leeuwenhoek and his works. According to some [REF:2], the genius of van Leeuwenhoek is, probably, the best thing that happened to mankind. His discoveries helped us make the world a better place to live in. The impact of the works of the "Father of Experimental Biology and Microbiology" to the scientific world of his time is difficult to estimate, but it was a significant breakthrough to stimulate a new wave of research. People became aware of another world crowded with innumerable tiny living creatures.
At the time of van Leeuwenhoek, who lived in the Dutch "Golden Age" and the rise of the Dutch East (and West-) Indian Company, the city of Delft was an important Centre of science and culture.

Johannes Vermeer, View on Delft, Schie-quay (In the middle: Shiegate and Old Church)
[Click on this image for a guided art history tour through this painting.]

Doctors and apothecaries in The Netherlands would collect objects in the naturalia category as well as scientific instruments such as microscopes, to assist their studies. Van Leeuwenhoek took a keen interest in new ideas from scientists both in his own country and abroad, and exchanged objects and information with other collectors as can be read in his works.

To day, we can see the pathogens, which are invisible to naked eyes, with the vision invaluable gifted to us by van Leeuwenhoek and can fight against them. With future technology, we will be able to hopefully sort out and solve many other health problems, as well as environmental problems like pollution. The latest researches in DNA replication and unveiling of the genetic code are all thanks to that brilliant vision, first striking the eyes of the genius Antonie van Leeuwenhoek.


The approach

In many publications the assumption is made that Leeuwenhoek´s fascination for microscopy was inspired with cloth-trade. On the other hand, it is told that after reading the book of Robert Hooke, Micrographia (1665), he became interested in microscopes. Already as a young and curious boy he might become interested in the new and popular branch of science, natural history, just like youngsters nowadays are intrigued by ICT and computers.
Antonie van Leeuwenhoek possibly started his favourite hobby during his residence in Amsterdam (1648-1654), at that time the city of the father of Jan Swammerdam, an apothecarian who owned a remarkable collection of Natural-History-objects and who stimulated young Antonie, as has been suggested by J. Van Lennep, W. Moll and J. Ter Gouw [REF:76]. Further it is mentioned that young Antonie van Leeuwenhoek learned the skill of glassblowing from a glassblower on a market at Amsterdam [REF : 88]

After his return to Delft (1654) van Leeuwenhoek continued his studies with the aid of self-made simple microscopes. Then, Antonie van Leeuwenhoek started to read carefully the works of Robert Hooke and systematically reran his experiments, as has been shown by Brian Ford [REF:4].

The best way to describe the works of Antonie van Leeuwenhoek is as follows: He used, by nature, an inductive approach (like Harvey). He started (somewhat arbitrary) with observations and measures, began to detect patterns and regularities, he sometimes formulated a hypothesis which he tried to verify, rather than formulating a solid theory. Though not always using a systematic approach, Antonie van Leeuwenhoek is credited for his lifelong and accurate attempts to quantify his observations and make it public.

In his works two basic principles can be seen:
[1] The structure of organic- and inorganic matter is based upon the same principle.
[2] In every organism (animal of plant) there is a close relationship between form and function.

Further, he emphasizes that (A) motility is the only available criterion for considering a microscopic object alive, and (B) the concept of the spontaneous generation is ridiculous ("a bad joke:Soo een roerlyck schepsel soude ontstaan uyt onroerlycke stoffe, dit soude een mirakel sijn").
In his missive of Jan 22th,1683, he was one of the first who mentioned the "struggle for life" principle.

In the beginning van Leeuwenhoek was a follower of the socalled dogma of the globulists : Every material (alife or dead) is build up of globules ; so bloodcells and yeastcells should consist of a unity of 6 globules. In finding "nothing but the truth" Antonie van Leeuwenhoek admitted chivalrously when he was wrong or made mis-interpretations.

Antonie van Leeuwenhoek, the amateur microscopist, was not prepared to draw logical scientific conclusions. He did not follow a systematic approach. But his concept was : careful observation, careful documentation, and the avoidance of premature conclusions.
Everything was worth studying: whether it was a drop of rainwater, pepperwater, seeds, wood, skin, open wounds, blood, brains, crystals, a beetle clashing against his window while doing his afterdinner nap, a hypothesis of Jan Swammerdam [REF: 59], Christiaan Huygens [REF: 86] -REF: 59], Boerhave or Harvey or an itch on his skin or his own stool. Van Leeuwenhoek observed nematodes, green algae, amoebae, infusoria, bacteria, the annual rings in wood, ovaria, muscles, bloodcells, fruit and seeds, insects and verms, frogs,crystals in wine and vinegar, pot-ash(=sodium) and much more.

Parasitoidism, Polyembryony, Pharmacological- and other experiments.

He was the first who observed the parasite Anisakis in the Hering: in a letter (Missive 96, Delft 1695) to Hendrik van Bleiswyk, van Leeuwenhoek warned about worms in a fresh hering, "Wormkens in de holligheit van de buyk van de haring."
Antoni van Leeuwenhoek described( for the first time correctly) the phenomenon of parasitoidism in insects in 1700. He drew a female parasitoid laying eggs in aphid hosts (Parasitism, REF: 37).
As early as in 1719 Van Leeuwenhoek discovered the phenomenon of polyembryony (more than one embryo) in an orange seed.

The first pharmacological experiments on nutmeg from the Moluccas (the most important trade of the Dutch V.O.C) containing the volatile oil, myristicine a psychoactive toxin, were performed by van Leeuwenhoek, around 1676. He frequently observed peppers in water, under the erroneous assumption that it had microscopic "spikes" to produce its effect on the tongue. Toxicological interest in nutmeg is of long standing. As early as 1676, Van Leeuwenhoek noticed that a volatile constituent of nutmeg killed or repelled mites.

Van Leeuwenhoek traced the life histories of various animals, including the flea, ant, and weevil, refuting many popular misconceptions concerning their origin. However, van leeuwenhoek did not prove the cause-effect relationship between bacteria and diseases. As early as 1530, Gerolomo Frascatoro (1483-1553,Verona) an Italian, suggested that syphilis and other diseases could be contagious (transmitted by direct contact with an infected person, contaminated materials, or infected air).

Van leeuwenhoek, [though not yet familiar with the useful characteristics of the microflora in the tractus digestivus], mentioned the phenomenon of contamination. After observing numerous little animals in pond-water, van Leeuwenhoek himself speculated about the following in a letter to the Royal Society (Delft 28th june 1715, page 68, Dutch edition) :

"In case a man cleans his beer- and wine glasses in such a pond, then who knows, how many little animals could keep stick (on those glasses), from which some of them could be transported into our mouth;...."

Notwithstanding the fact that this is clearly a proof of common sense, nobody seriously payed attention to this remark, at that time !

Dominantion of a phenotypic trait in rabbits.
Almost 200 years before Gregor Mendel (1822-1884) wrote his short monograph, "Experiments with Plant Hybrids," van Leeuwenhoek published a missive 38 to Christopher Wren (july 16th. 1683, page 9. edited by Cornelis Boutesteyn ,´t Rapenburg, Leyden) about a peculiar aspect of inheritance. In this letter, Antonie van Leeuwenhoek was the first ever who draw attention to a hereditary dominant phenotypic trait in male rabbits, living in the sand-dunes of the Netherlands (cross-breeding a grey domesticated male X a whitish female wildtype). This was pointed out by Clifford Dobbel in 1915.

Cryptobiotic animals were documented by Anton van Leeuwenhoek (1702) , observing tiny life forms in sediment collected from rooftops. He dried the "animalcules" to preserve them, and when he later added water he saw the creatures (probably Rotifers) begin to move around [REF:85].

Anhydrobiosis : In 1702, Van Leeuwenhoek was the first to describe the phenomenon of anhydrobiosis in a species of bdelloid rotifer, Philodina roseola [REF:84].

He discovered for the first time that living cells are composed of 80% water. Antonie van Leeuwenhoek was the first to use the technique of microdissections on insects and "obtained results which are remarkable even by modern standards" [REF:41].

Furthermore, in 1702, van Leeuwenhoek reported to the Royal (Scientific) Society of London that he had observed "a little clear sort of light in the middle" of a fish blood cell he had been examining. This description of what was later called the cell's nucleus was the first suggestion that animal cells had an internal structure [REF:63].

Leeuwenhoek was the first to observe (or rather descibed) the phenomenon of conjugation in Vorticella, though he misunderstood the process: erroneously he considered the nucleus to be "Ovaria".

Lucky enough for the world, he was not at all "influenced" by the usual academic theories of his days. Though not a professional scientist he had the right attitude: Only after critical verifying and repeating his observations he described his findings. Some of his observations are only now coming to light. Van Leeuwenhoek also may be credited with the establishment of a pioneering example of forensic microscopy [REF:4].

and Mineral objects.

Van Leeuwenhoek examined everything, ranging from samples of about 200 biological species to mineral objects and crystalls; [he even experimented with the compound of gunpowder and advised a chief-commander of the French army to shorten the barrel of a gun "from 18 feet to 14 feet" in order to reach maximum effect].

Protozia, Bacteria and Spermcells.

Leeuwenhoek made accidental discoveries: tiny organisms, known today as protozoa, bacteria and spermcells. But the student Johan ("Louis") Ham ( Ham was elected as a Lordmayor of the city of Arnhem) was the first who discovered these "germs". Van Leeuwenhoek has never asserted that "human sperm is abundant of little infants" and he could become angry if others tried to mis-interpret his findings. He concluded (a novelty for his time) that fertilization occurred when the spermatozoa penetrated the egg.

He was able to work with full independence of theories of his fellow scientists and made sharp distinction between the empiricism and speculation that marked the sometimes chaotic world of seventeenth-century science. In opposition to the general belief that van Leeuwenhoek was the man who invented the "Homunculus idea" in spermcells, he was very sceptical about this. It was either a scholar that launced this misconception or Jan Swammerdam in 1658.

Robert Hooke (1653) and Malpighi (1653) exploited a compound microscope with three lenses in their anatomical or embryological research before van Leeuwenhoek. After a century this concept was improved by John Cuff.

Engraving of the "New Double Compound Microscope ", constructed and improved by Mr.John Cuff (± 1750), see Henry Baker [REF 80] and [The Gemmary Scientific Instruments].

However, van Leeuwenhoek was the first to see life under his microscope (with one simple spherical lens of suberb quality). In 1676 or earlier (NOT JUST 1683 when he described bateria in the plaque !)van Leeuwenhoek observed living things in pepper-water and wrote this discovery in a letter (9 oct. 1676) to Henry Oldenburg,(ca. 1620 - 1677) the first editor of the Royal Society’s journal Philosophical Transactions, (see hereafter) and intentionally underestimated the total account. He called them ‘animalicula’, what we now call Protozoa from the greek “first animals”. The arguments of Aristotle, and others about the Generatio Spontane were muted by the observations of Antoni van Leeuwenhoek. The first serious attack on the idea of spontaneous generation was made in 1668 by Francesco Redi, an Italian physician and poet.

A Critical remark on the work of contempararies.

Sometimes, to Antonie van Leeuwenhoek it was not unpleasant to criticize the work of other microscopists of his time. On following passage (Missive 57, 6 aug. 1687 to the Royal Society, pp 90) he was " not amused" by the work of a certain Johannes Fransiscus Griendelio, saying:

" People has told me and spoken highly about a certain book, dealing with microscopical observations, containing exceptionally magnified illustrations, a book that was put up for auction at the Frankfurtian fair. I was very eager to buy this book, hoping I could learn something. However, as soon as I had this book, named Micrographia Nova, edited by Mr. Joh.Fransisco Griendelio[REF: 89] , I saw that it was of no value : because the little creatures depicted in that book, such as the Louse , the Flea, the Ant etc. were large enough indeed, but they were drawn very imperfect and deformed. It do not know whether this is because the lack of qualified magnifying glasses, or it is due to the poor designer."

The Ant


The first reaction

Van Leeuwenhoeks discovery of bacteria was not immediately accepted by scientists.
His letter to the Royal Society announcing the discovery of bacteria caused such doubt at the Royal Society that he had to enlist an English vicar, as well as jurists and doctors, to confirm that his report was based on true observations. Robert Hooke later repeated the experiment and was able to confirm his discoveries.

The Royal Society wrote a letter asking him if he would rent his microscope for few days. But Leeuwenhoek did not send his ‘loving’ instrument. To confirm Leeuwenhoek’s reports, the Society appointed two scientists – Nehemiah Grew, the plant anatomist and Robert Hooke, the microscopist. They attempted to validate Leeuwenhoek’s observations. First time they failed, casting doubts on his report. However, Hooke again tried using a microscope with 330 X (power of magnification) and confirmed Leeuwenhoek’s success. Both scientists confirmed that their observations were similar to those described in the letters by Leeuwenhoek. Now, the Royal Society accepted Leeuwenhoek as a scientist and declared him as the discoverer of bacteria.
Antonie van Leeuwenhoek was elected a Fellow of the Royal Society of London in 1680. [REF:3]

Van leeuwenhoek refers to a letter he wrote to the Royal Society (1675) in which he says:

"When I observed for the first time in the year 1675 very tiny and numerous little animals in the water, and I announced this in a letter to the Royal Society in London, nor in England nor in France one could accept my discovery, and so one still does in Germany, as I have been informed."

The reader has to realize that everything van Leeuwenhoek published and wrote to the members of the Royal Society was completely new, undiscovered and unknown, so in the beginning his observations were viewed with scepticism (even by Christian Huygens). This can be judged from the next quote:

In a letter, Hendrik Oldenburg, the Secretary of the Royal Society, London, wrote the following to Antoni Van Leeuwenhoek, Delft, Holland, 20th of October, 1676:

Dear Mr. Anthony van Leeuwenhoek,

Your letter of October 10th has been received here with amusement. Your account of myriad "little animals" seen swimming in rainwater, with the aid of your so-called "microscope," caused the
members of the society considerable merriment when read at our most recent meeting. Your novel descriptions of the sundry anatomies and occupations of these invisible creatures led one member to imagine that your "rainwater" might have contained an ample portion of distilled spirits--imbibed by the investigator. Another member raised a glass of clear water and exclaimed, "Behold, the Africk of Leeuwenhoek." For myself, I withhold judgment as to the sobriety of your observations and the veracity of your instrument. However, a vote having been taken among the members--accompanied I regret to inform you, by considerable giggling--it has been decided not to publish your communication in the Proceedings of this esteemed society. However, all here wish your "little animals" health, prodigality and good husbandry by their ingenious "discoverer.

Leeuwenhoek wrote a crushing comment about this subject after the decease of van Oldenburg.

Underestimation of the amount of "little animals" in a Missive, oct. 1677

In a missive, written to William Brounker after the decease of Henry Oldenburg (Delft October 5th, 1677) Van Leeuwenhoek "confessed" to have underestimated intentionally the amount of little animals in a drop of pepperwater, otherwise the Lords of the Royal Society would not believe it (no credit) !

"Ik hebbe doorgaans in ´t geven van de atteftatie,
de Heeren gerecommandeert, dat zy het getal maar half zoo veel zouden ftellen, als zy oordeelden te zien, omme redenen, dat het getal van de dierkens, in zoo een kleyne quantiteit water, egter zoo groot zoude zijn, dat het by veele geen credyt zoude vinden , want doen ik in mijn Miffive van den 9. October 1676. ftelde, datter in een droppel peperig water, meer dan 1000000. levende Schepfels waren, hadde ik het getal met waarheyt, wel agt maal zoo veel konnen begrooten. enz.

A.van Leeuwenhoek.


However, fourty years later Antonie van Leeuwenhoek, describing Barley in his Letter of June 12, 1716 (directed to "Cinck, Narrez, Rega and others") gives thanks for receiving a golden purse and a commemorative silver medal for his work, writing as follows :

"..the more so as my work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men."


Official members of the Dutch government visited van Leeuwenhoek only once, at his eightieth.
One of these dignitaries wondered: "Should not we go to reward all this work ?".
The answer was:"Yes that´s what we all are saying, but why we don´t ?". They never did ![REF:76]



The Janssen microscope-tube about 1595.
(Father Hans and son Zaccharias Janssen).Hans sometimes is named Hans Martens.
Its magnification was up to 20X and it is the forerunner of the compound microscope
and of the telescope.

no permission to copy
Oldest known drawing of a compound microscope (From the diary Isaac Beeckman, Middelburg, The Netherlands anno 1625)

Below: Van Leeuwenhoek Simple Microscope design type I (1670) in vertical position [32].

The quality of van Leeuwenhoek´s so-called "primitive microscope" (design type I) was far superior to all other microscopial designs for over 170 years.
The overall van Leeuwenhoek microscope length, with object spike in position before the lens, is 3". A pointed rod 1/4" long for mounting specimens is screwed into a 13/16" long metal block or stage.
The simple biconvex lens (DIAMETER 0.7 mm towards the objectside and 0.6 mm towards the eyeside) is mounted between two thin silver oblong plates 15/16" by 1 7/8" at their greatest dimensions.The simple biconvex lens is clamped in a concavity formed between the plates and secured by four equidistant rivets. The distance [lens - object] is about ½ mm.
A screw, 13/16" long, (28 convolutions pro inch) aligns the stage and object with the lens while a thumbscrew on the eye side pivots the metal plates giving lateral motion. Focusing is achieved by a second thumbscrew which passes through the stage at one end and presses against the plane of the oblong plates. Turning the knob of the object holder acts as a further focusing mechanism.

Original Microscope van Leeuwenhoek

An example of this microscope in possession of the Carl Zeiss corporation.

Microscope type II:"the AALKIJKER" (Eelwatcher or Fishglass) made of brass [35]

The etching of the microscope "The Aalkijker or Fishglass " (design type II, 1688-1689) was first published in "Brieven pag.306, Cornelis Boutesteyn,Boekverkoper ´t Rapenburg,1688,Leyden.Ist Edition. Holland". Christian Huygens (1629-1695) also made a drawing of this microscope. This instrument was used by van Leeuwenhoek in studying bloodcirculation of "The EEL" in a glass-tube at the right (W-Q).The diameter of the lens of the Aalkijker micriscope has been estimated as follows: 1.8mm towards the objectside and 1.2 mm towards eyeside, according to the biohistorician Abraham Schierbeek (1887-1974) [REF:82].


Image of "The Eelwatcher microscope". This image is protected.

Microscope the Eelwatcher- Aalkijker
See a model of this design on the following link:Virtual Museum

Drawing of van Leeuwenhoek´s microscopes by Henry Baker (1756),REF 80.

[Some coral species and dimensions in micrometers]

Design of a microscope adapted for use with a Camera Obscura (1871)
to make photomicrographs

The first published illustration of a camera is in a book from 1545, by the Dutch mathematician and astronomer Gemma Frisius (Dokkum 1508- Leuven 1555).
Microscope and Camera Obscura,Design 1871

Carl Zeiss compound monocular microscope. Old Zeiss instrument improved by Dr.Ernst Karl Abbe.

This instrument is the progenetor of all modern compound microscopes in use today. The instrument is a small microscope with a horseshoe base and a round pillar. The body-tube is attached to the pillar by a short arm and focusing is by the screw on top of the pillar. A swinging mirror is attached to the bottom of the stage. The instrument has a mahogany box in which it lies sideways. Signed B: 4868 by Carl Zeiss, Jena. This consist of two optical elements: an objective and an eyepiece. See model about 1878, leftside.

NOTE: In 1854 Rudolf Winkel sets up a mechanic's workshop in Göttingen to show his microscopes. Simple ones at first, compound ones later. Ernst Abbe first visits Winkel in 1894. In 1911, Carl Zeiss becomes the principal shareholder of the company. See Model Winkel, monocular brass microscope tube, about 1885, signed nr 20754, rightside.

Carl Zeiss microscope Design 1878


Below: Carl Zeiss Jena Laboratory compound monocular microscope
This instrument has Diaphragm and Köhler's objective [model about 1930] Carl Zeiss signed :223693.
The van Leeuwenhoek volumes.
CarlZeiss microscope Design 1930
First issues of the complete set of Leeuwenhoek's letters
in their first appearance in the original Dutch.

Zeiss design 2002

Sophisticated modern Zeiss binocular microscope (design 2002).
Connected to a computer to produce digitalized images.


Register of Books, Missive 28 (first issue in Dutch), following the first 27 Missives.

Leeuwenhoek Register of Books

Left:Titleplate Romyn de Hooghe, fecit 1685 (Boutesteyn Ed.).
Right:Titleplate J. Goeree (printer and engraver born 1670, died 1731), fecit 1716 (Adriaan Beman Ed.)
Beneath :Titleplate, van Schaak fecit 1696 (Hendik van Crooneveld Ed.) "Occult Qual".
Note: [The sequence of the titleplates is different from the Latin Editions]

Titleplate de HoogheTitleplate Beman

[Click on the image:Explanation of this titleplate by Pieter Rabus in original Dutch]

Van Leeuwenhoek,frontispiece portrait (Abraham de Blois fecit 1688, Cornelis Boutestyn Ed.)

Frontispiece van Leeuwenhoek


Short Biography

It is mentioned that Neeltje van Hogenhouck and Sebastiaen Cornelisz. van den Berch or van den Bergh ("veertig-raad" and "schepen" in Delft) became the great-grandparents of Antoni van Leeuwenhoek (Thonius Philipsz) [REF:44]. The name of at least one sister of van leeuwenhoek is known: Catarina van Leeuwenhoek, married in 1655 with Claes Jansz. van Leeuwen, living in de Hoogstraat, Old Townhall at Rotterdam [REF:75]. Both the grandfather and the great-grandfather of van Leeuwenhoek were beer-brewers at Delft.

Antonie van Leeuwenhoek born in Delft, The Netherlands, on 24 Oct.-1632, died 26 Aug. 1723 at great age (almost 91 years). He lived in exactly the same period [REF:36] as the English scientist Christopher Wren (20 Oct. 1632 - 25 Febr. 1723) and the empirist and philosopher John Locke (29 Aug. 1632 - 20 Oct. 1704). Being a Dutch Reformist (probably a moderate Calvinist) [REF:68] it was told he had a friendly and polite character: FOR HIS OBSERVATIONS,HE WOULD NOT CATCH A DOG FROM THE STREET, SAYING "PERHAPS THE OWNER IS LOOKING FOR THE POOR CREATURE". He used to speak with sympathy and compassion about his fellow-men and ill people and visited them.
[ For instances the lepers in a leper-hospital at the city of Haarlem and this does not match to the view of some authors that he had an abstinent character].
He usually refused to teach or to accept donations, saying:"Otherwise I would surrender myself to slavery; I prefer to be a free man" (see missive XX to Leibnitz, March 13. 1716).
Gottfried Wilhelm Leibnitz who visited van Leeuwenhoek and who was very impressed by his works, made a proposal to establish an academy or college for people to learn about microscopy, but van Leeuwenhoek refused saying that " it could be used but to make money by means of science, or to become respected through erudition : "om door de wetenschappen gelt te bekomen, ofwel door geleertheyt geagt te syn" [REF:57].

He seemed to be a very accurate observer with a very sharp vision. His father, Philips Thoniszoon a basket-maker, died young (1638). His mother, Margaretha Bel van den Berch, was the daughter of a beer-brewer, Jacob van den Berch. Most likely, Antonie van Leeuwenhoek, who signed as :"Antoni van Leeuwenhoek", was named after his grandfather, "Thonis". The surname "Leeuwenhoek" was adopted by Antonie on account of the fact that his father was the owner of a house at the corner of the Leeuwenpoort (Liongate) at Delft. His mother send little Antonie to a school at Warmond (near Leiden) and his uncle (deceased 1648), living at the small village Benthuizen, teached him in the pinciples of mathematics and fysics. However Leeuwenhoek never finished an academic study. In 1648 (Treaty of Munster, the end of the eighty-years war) his mother send Antonie to Amsterdam to learn for a book-keeper. Indeed Antonie was contracted for a job at a scottish textile merchant William Davidson. During that period Antonie might have formed a friendship with wellknown scientists and artists Christian Huygens the astronomer [REF:62] and Jan Swammerdam. The suggestion has been made that the young Antonie "could have met" Rembrandt Harmenszoon van Rijn: both were Dutch Reformed and they visited services in the Old Church at Amsterdam.

In 1654 van Leeuwenhoek moved to Delft and he bought the house "Het Gouden Hoofd" (The Golden Head) in the Hippolytusbuurt. He started a fancy-wool shop and contracted for a job as "kamerbewaarder der kamer van de Heren Schepenen te Delft", (chamberlain of the town's law courts at Delft).
It is said that the painter Johannes Vermeer, born in the same year and week at Delft, was his friend (see hereafter).

After his return to Delft in 1654 he constructed his first simple microscope.After a while he got a job as a surveyor (1669) and a wine-taster (1679). He appeared to have plenty of time for his hobby as a lens-grinder and an amateur microscopist and succeeded brilliantly in designing his own simple-microscope. He tried to show that living structures are made up of very tiny elements and components. He observed that living cells for about 80 % consisted of water. Only after repeatedly and thoroughly observations he published his findings. He refused to adopt any (scientific) theory without verifying. The driving force for his research undoubtly was his admiration in "the Creations of God" as he beared testimony in his works abundantly.

In 1665 he married (for the first time) to Barbara de Mey the daughter of an English silk-merchant (Elias de Mey and Maria Viruly] from Norwich and the couple became five daugthers. Only the eldest daugher Maria (22 sept 1656-25 sept 1745), survived Anthonie. After Barbara died in 1666 he married for the second time (January 25, 1671) to Cornelia Swalmius, the rich and well-educated daugther of Margaretha Uytenbroeck and Cornelius Swalmius a tradesman and governor of Valkenburg,a small city near Leiden. It is believed that Cornelia stimulated Antonie in his microscopic observations very much. Most likely, his father-in-law could take advantage of the skills of Leeuwenhoek´s microscopial findings. A letter of van Leeuwenhoek to Cornelius Swalmius, his father in law, gives evidence of this.

Until 1673, the world was not aware of Antonie van Leeuwenhoek. On 28 april 1673, just four month before his dead, the physician Reinier De Graaf (born in Delft) and a member of the Royal Society in Londen, wrote a letter to the secretary Henry Oldenburg to introduce Antoni van Leeuwenhoek and turned attention to the quality of his microscopes. From that time on Van Leeuwenhoek could publish his discoveries in his "missives" to the Royal Society. Only once, in 1668 van Leeuwenhoek visited London at the invitation of Robert Hooke. This was during the reign of the Dutch "Stadtholder" William III of Orange King of Great Brittain and Ireland between 1686-1702 and who was married to Maria Stuart II, daugther of Jacobus II [REF:54].
In 1678 van Leeuwenhoek was the curator and testamentairy executor of Johannes Vermeer. His second wife Cornelia died in 1694. The only child from this marriage died at very young age. Antonie van Leeuwenhoek was cared for by his daughter Maria till his death in 1723.
He continued his observations until the very end of his life.Just 12 hours before he died Leeuwenhoek wrote two letters to the Royal Society.Van Leeuwenhoek is burried in Delft (Old Church).

Antony van Leeuwenhoek suffered to a rare disease "Leeuwenhoek-disease", Myonuclonus respiratorius, Respiratory myoclonus - repetitive involuntary contractions of the diaphragm and accessory muscles of respiration [REF:11], (see also below).


Who constructed the first microscope ?

From the earliest days in Alexandria (circa 300 BC) when Euclid described the laws of reflection in Optica, the science of optics has fascinated and challenged society's most brilliant minds. The microscope is but an instrument, a tool. It is said by some people that through the invention of the microscope, humankind lost its naivety *).The precursor of the microscope are "glasses". Legend has it that St. Jerome (St. Hieronymus, 340-420 AD) invented glasses. However, several ancient manuscripts give datable evidence of the state of refraction and optics throughout the ages.( 2nd Century BC: Claudius Ptolemy, 1st Century AD: Seneca, 962-1038 AD: Arabian Scholar Alhazen)[REF:1].
In the 20th century it was believed that the famous "Lanyard Lens" discovered at Nimrod (datable 721-705 BC, Mesopotamia) by Austen Lanyard (who also discovered Ashurbanipal's library at Nineveh in 1850), could be "the first lens", but nowadays this is doubted. Pliny the elder (23-79 A.D.) records 'Nero princeps gladiatorium pugnas spectabat zmaragdo" and this vague reference to Nero (presumably he was short-sighted, myope) watching gladiatorial contests with an green emerald has been read to mean that he used glasses [REF:39].

The oldest known drawing of a microscope is found in the diary of the Dutch merchant and physicist Isaac Beeckman (1588-1637), founder the the molecular theory and who set up, in 1628, the first European meteorological station : Diary Isaac Beeckman (REF: 58-59), Middelburg, 1625 ,The Netherlands, (see above, old microscopes). The first known description has been made by the eccentric Cornelis Drebbel, Alkmaar The Netherlands (1619), who grinded lenses, spectacles, constructed spy-glasses and microscopes and allegedly "is the inventor of a perpetuum mobile (motion machine, which told the time, date, and season, and was mounted in a globe on pillars) "[REF:71]. It is generally accepted that Leeuwenhoek could not be the inventor of the microscope, nor Malpighi. The first who designed a microscope was Zacharias Jansen OR Janssen (1580? -1640) working in the Netherlands late in the 16th century as a spectacle maker or, more likely his father Hans Janssen (died about 1595) at Middelburg, in the province of Zeeland The Netherlands. Hans and his son Zacharias Janssen are mentioned in the letters of William Boreel (the Dutch envoy to the Court of France) as having invented a 20X magnification microscope. However Jan Swammerdam (1637-1680 ), Robert Hooke (1635-1703) and Malpighi (1628-1694) were the first scientists who used microscopes for their research in histology. In 1625, just seven years before van Leeuwenhoek was born, Cornelis Drebbel (1572-1633), inventor at the court of King Jacobus I of England and "physicist", published an accurate description of a simple microscope, presumably after the design of Zacharias Janssen. Antonie van Leeuwenhoek considered Drebbel as a charlatan but Huygens praised Drebbel !
Jansen subsequently extrapolated this approach to visual amplification by creatively attaching two such lenses at opposite ends of hand-held tube. Janssen’s device was unquestionably primitive, but the microscope (from Greek words meaning "to see small"), would shortly reveal a hitherto unimagined realm of life.

The famous Dutch Huygens-family was very interested in the findings of van Leeuwenhoek. Already in 1621, the father of Christian Huygens (Constantijn) studied the microscope of Cornelis Drebbel. By request of Constantijn Huygens (1596-1687) his son Christian Huygens made a translation (summary) of the first letter of van Leeuwenhoek in behalf of "The Academie Royale des Sciences (1676)". Christian Huygens (1629-1695) ,who constructed his first microscope in 1653, also made a drawing of the "Aalkijker microscope or Fishglass" (Universiteitsbibliotheek Leiden, Hug 6. Fol. 37r).
The elder brother of Chistian, Constantijn (1628-1697) is known for his travelstories and his sketches.

The socalled aquatic microscope was invented by Christian Huygens van Zuylichem. He originally designed this microscope around 1678 and published a sketch in his book "Oeuvres Complètes de Christiaan Huygens".In his work, Huygens was one of the pioneers of the so called "scientific revolution". Modern science was to a large degree established in the seventeenth century, and Huygens was one of the persons who brought this about.

User-guide van Leeuwenhoek microscope:

In 1756 Henry Baker published the well-known detailed description and user-guide of the van Leeuwenhoek microscope, [REF 80], see also Baker´s engraving.

Henry Baker,Nuttig gebruik van het Mikroskoop, page 453:

Een naauwkeurige Befchryving van de zesentwin-
tig Mikroskopen
, en de Voorwerpen tot dezelven behoo-
rende, vervat in een klein Kistje, ´t welk de Heer Leeu-
, by zyn affterven, aan de KONINKLYKE SOCIE-
TEIT VAN LONDEN hadt befproken, werd, nu veele Jaa
ren geleeden, door den Schildknaap Martin Folkes (president of the Royal Society in 1757) , aan
die Societeit vereerd, en is in N.380 van de Transactien
te vinden.

A first edition of this work was published by Henry Baker in 1742:
"The Microscope made easy".


In 1850 Pieter Harting (Collection of Microscopes, University Museum, University of Utrecht, The Netherlands) discovered the Van Leeuwenhoek microscope and the Huygenslens in a collection at the University of Utrecht [REF:45]-[REF:47].


Hans Lippershey (1570-1619) a Dutch spectacle-maker from Germany, was the first who gave a description of a telescope (the socalled "Dutch Spy-glass") in 1608 and improved the simple microscope; Galileo Gallilei (REF: 59) took advantage of Lippershey´s invention in 1609 by increasing the distance between the lenses to make a better telescope for his observations to the Moon and the Planetary system. So from that time on it appeared the Earth was not at all the center of the Universe !

Quality of the van Leeuwenhoek microscope

As a matter of fact, the design of simple microscope of van Leeuwenhoek (see above) was nothing more than a loup : A lens of superior quality in a holder. The way of Light-rays when an object is observed through a loup, magnifying glass or simple microscope is shown in the figure below
[ f = focal distance, b = visual angle].

Lens quality in these magnifying glasses was often poor (due to chromatic aberration and airbubbles) so the images were not very clear.
According to Pieter Harting a second loup could have been used to control the quality of the microscope lens during the grinding process.
Cittert [REF:46] and others [REF:21] made the suggestion that van Leeuwenhoek could have grind or polish his lenses with the aid of very small pieces of glass [REF:21]. Others mentioned that he used abrasive powders [REF:50]. However also the method of glass-blowing (a method probably adopted from Robert Hooke and Johannes Hudde - 1624-1704- a scientist and lord mayor of Amsterdam) was used by van Leeuwenhoek to produce a small "spherical drop of glass" [REF:57].

In general, the quality of a light microscope (the objective or the lens) depends on many variables, such as:
Numerical aperture (NA) : a measure of the ability to gather light and resolve fine specimen detail at a fixed object distance.
Resolution (resolving power) (mm) : defined as the smallest distance between two points on a specimen that can still be distinguished as two separate entities.

Resolution is a somewhat subjective value because at high magnification, an image may appear unsharp but still be resolved to the maximum ability of the objective.
Numerical aperture determines the resolving power of an objective.

The following formula by Ernst Abbeé (1840-1905) is used to establish the resolution-limit D of a lens
Formula Ernst Abbe Resolution
[n = Refraction-index (air, oil or water). Numerator = wavelength,lambda. Denomerator = NA = numerical aperture]

The magnification of the simple microscope is defined by the formula:
Formula Magnification
[M = magnification. f = focal distance of the lens, 250 = punctum proximum, accomodation point of the normal eye = ± 250 mm]

We are well informed about the magnification power of the Leeuwenhoek microscope. See A.Schierbeek in Antoni van Leeuwenhoek, 1963,[REF:82 ] and Henry Baker [REF:80]. Due to his interest in the study of Natural History, van Leeuwenhoek started to grind lenses himself and constructed his own microscopes. His microscopes which he crafted himself by hand had powers of magnification ranging from 50X to [at least] 300 X and some of his ("sharp-sighted high quality") microscopes probably could reach magnifications of about 500 X. In several studies of the few remaining original (though used) microscopes this could be established and resolutions as good as 1 micron (1/1000 mm) could be distinguished,(the best instruments had a resolving power of about 1 micrometers or less. ). The focal distance of the lens in a van Leeuwenhoek microscope of superior quality should be < 1 mm [REF:34] - [REF:46]. According to calculations made by van A. Schierbeek [REF:82], based on Leeuwenhoek´s letter (12 nov.1680 to Robert Hooke, pp 57-60 ,see image below, published in the Dutch edition by Hendrik van Kroonevelt) the magnification of the van Leeuwenhoek´s microscope could reach 480x at least.

Leeuwenhoeks´s calculation of magnification [12 nov.1680 to Robert Hooke].
Leeuwenhoek writes: "Let me imagine a sandgrain as big as the a body ABGC (the big circle)...and an animal walking or swimming on this sand as big as Fig.D. of which the axis is one-twelfth ......"

Experimental relationship [magnification X, resolution in mm] of the Simple Microscope
At L: An used Van Leeuwenhoek Microscope of normal quality [Dr. P.W. van Cittert,1943]

Relationship Magnification - Resolution

The lenses reaches ± 2 mm diameter or less ! Until 1825, the compound microscopes could only resolve as well as around 5 microns.
Antonie van Leeuwenhoek used single lens microscopes with extremely short focal lengths. This enabled him to see bacteria, the "little animals", spermcells and the very little globules (i.e. chloroplasts) in the green leaves for the first time in history. To oberve the objects with this simple microscope, the apparatus has to be placed closely before the eye in vertical position, against the light. He improved the resultant image by taking advantage of the optical principle that the least light distortion occurs close to the central ray. The lens was a double convex sphere, having a short focal length. When an object is placed nearer such a lens than its principal focus, i.e., within its focal length, an image is produced that is erect and larger than the object.
The object to be examined was raised or lowered and rotated upon its axis by a coarse-threaded-screw. Meyer [REF:49] speculates that Leeuwenhoek's hand-held microscopes were only fit for demonstration purposes,and that for his researches, Leeuwenhoek used a compound microscope, which he kept secret and was lost after his death.

To select the parts of his study-objects he was interested in, van Leeuwenhoek first used a magnifying mirror, then he used a "common" microscope or a magnifying-glass and if not satisfied, he took his "sharp-sighted" microscope or "another way of observing, namely through a more magnifying microscope" [Missive Sept.17th, 1683].

Most of his 500 microscopes were made of silver, gold or copper (or brass). His lenses were made of crystal, quartz of even (scratch resistent) diamond. He never published the way of how to make his lenses, so he carried this secret with him to the grave.

The lens of the van Leeuwenhoek microscope is catched between two (copper,silver or brass) plates and and with a pinhole to hold a tiny drop of fluid. He did not make his drawings himself but he instructed his "Scriba" or "Tekenaer" (limner) carefully how to draw the things he observed and either approved or rejected those drawings. The identity of these limners is uncertain, though in a letter (april 4th, 1687, pages 7 - 15), van Leeuwenhoek gave the following information about his limner:

"To observe the thickness of the canals in a tooth,.... I handed my limner (who is a copperplate engraver),the magnifying glass and ordered him to draw the things he could see without telling him what is was."

Then the engravings could be made on copperplates.At the moment only nine original microscopes have survived time (in musea or in private collection). Many times people have tried to imitate his microscopes. (Nowadays it is possible to make a replica of his microscope [REF:32])
Enhancing the quality of the microscopical objects.

Antonie van Leeuwenhoek used a saffron-coloring procedure to enhance contrast in his objects. Furthermore, he sometimes filled a small glasstube with clean water containing living material and fixed the tube with the aid of two silver springs onto his microscope-plate. Probably this method caused some extra magnifying effect, due to the greater refraction-index of the water in the glasstube. When using a lens of diamond (refraction-index twice as large as water) the magnifying effect even could be more !

It is not clear how van Leeuwenhoek obtained the necessary illumination to achieve his remarkable results. The protozoologist Cecil Clifford Dobell (1886-1949) suggested that he might have discovered some simple method of dark-ground illumination, whereas Barnett Cohen pointed out that the optical properties of spherical drops of fluid containing the objects under observation may have been used by van Leeuwenhoek [REF:41].

To investigate the same object, Antonie van Leeuwenhoek sometimes used several of his selfmade microscopes as well as magnifying glasses,"Vergrootglazen", and he not always used his own microscope. Occasionally he used a different microscope, possibly a sophisticated design made by Johan (or Johan Joosten) van Musschenbroek (1660-1707), a high power brass simple microscope with an adjustable fine focus [REF:87] , or a microscope constructed by Christian Huygens (1629-1695), [REF:14] as one can read in his "missives" from 1722. This microscope is the socalled "De Aalkijker" and van Leeuwenhoek used it to study the blood-circulatory system in the tail of an eel in a glass-tube (filled up with water or oil) (see image : "Aalkijker-microsope or Fishglass").

After a long series of experiments (starting from 1683 up to 1688) van Leeuwenhoek was the first to proof that the bloodcirculatory system was a closed system and that the pulsations were caused by the heart-rhythm.
"Den Waaragtigen Omloop des Bloeds, Alsmede dat de Arterien en Venae Gecontinueerde Bloed-Vaaten zijn, Klaar voor de oogen gestelt."

[NOTE: Leonardo da Vinci (1452 - 1519) already studied the human circulatory system.]

It is suggested that the fact that van Leeuwenhoek had close relationships with textile merchants (as was his father in law) was not insignificant. At that time the quality of textures was judged by magnifying glasses. In contrast to the compound microscopes of Robert Hooke and others the microscope of van Leeuwenhoek only had one single lens and thus a minimum in optical aberrations. Due to this simplicity and the high quality of the grinding procedure the van Leeuwenhoek microscopes were the very best, until 1825. One could observe details up to 1 /1000-th millimeters (1 micron). Only after 1825 the compound microscope has overtook its disadvantage by corrections on the objectives and a better illumination system. A lunar crater (Leeuwenhoek Lunar crater, position 29.3S and 178.7W, 125 km diameter) is named after him [ Leeuwenhoek crater].


Generatio Spontane

The theory of the Generatio Spontane (Aristotle, Vergil) predicts that living creatures can be originated from inanimated material. It does NOT say that living creatures could originate from spoiled meat or dirty laundry !
The doctrine of the Spontanous generation was accepted without question until the Renaissance.
On the otherhand, van Leeuwenhoek believed that "his animalcules" were formed from the "seeds" or "germs" of these animalcules, which were always present in the air. Even Louis Pasteur did not deny the existence of the Spontaneous Generation : Under experimental conditions he showed that the Spontaneous Generation could not be proved.

The origin of life remains a mistery even if we a-priori accept the theory of the abiotic formation of buildingblocks of life (amino-acids,nucleotids and sugars from methane, ammonia and water vapor) under primitive atmosophere conditions and activated by the radiant energy of the sun. However, these experiments ( biochemist Aleksandr Ivanovich,1894-1980 and geneticist John Burdon Sanderson Haldane,1892-1964) lay far beyond the perception of scientists in the XVIIth and XVIIIth century.
Oparin outlined a way in which basic organic chemicals might form into microscopic localized systems - possible precursors of cells - from which primitive living things could develop. He cited the work done by Dutch chemist H.G.Bungenburg de Jong on coacervates and other experimental studies, including his own, into organic chemicals which, in solution, may spontaneously form droplets and layers.


Van Leeuwenhoek was a creationist (everything exsists by the creation of God) and (lucky for modern Science !) he disputed the general Aristotelian view of his time that living organisms could be spontaneously generated.
Although van Leeuwenhoek did not made the cause and effect-relationship between microbes and diseases directly, he pointed out that after a good sanitary attitude only a few microbes could be observed ! He was the first to study spermatozoids in which he "discoved nerves and muscle structures". According to the general view one should observe a little human being in there : the homunculus (Jan Swammerdam). Emanuel Swedenborg a Swedish scientist (Stockholm 1688-1772) denied the existence of bacteria. Swedenborg claimed these are mere 'particles' of living matter that put on capricious, transitory forms. He maintained that Antony van Leeuwenhoek's observations of bacteria in human saliva were an observational artifact !
On several passages from his work, and especially in his Missive Sept.16th, 1692 (see below) van Leeuwenhoek, studying the reproduction of the Eel, "makes no ceremony" of the theory of Generatio Spontane. He investigated the generation of eels and proved that they originated,like the other animals he studied, from cellular interactions between a male and a female of the kind, saying (page 509,top):
"We are too credulous and therefore we assume that living creatures originate from putrefied-materials and so on ...."

Louis Pasteur [24] quotes these passages in his work (1862).

Missive 75, 16 sept 1692:"Studying the reproduction of Eel,
no Generatio Spontane". Antonie van Leeuwenhoek wrote :
"We are too credulous and therefore we assume that living creatures originate from putrefied-(decayed) materials and so on ....."(page 509 first paragraph)

Delft in Holland den 26.September 1692

Missive 75

Concept of Fertilization

Ovists, Spermists and "the first essential material" of Van Leeuwenhoek.

Dutchman scientist Reinier de Graaf (Regnerus de Graaf, Delft 1641-1673, Catholic) introduced his friend Antonie van Leeuwenhoek to Henry Oldenburg, secretary of the Royal Society, on 28 april 1673, just four month before he died). De Graaf proposed that:
1. The egg contains an entire human in miniature and that semen only stimulates its growth.
2. All characteristics are thus inherited from the mother.
De Graaf was the first person to describe the ovarian follicle (vesicles) in which human egg cells are produced (follicles of De Graaf).

This is known as the concept of the ovists (Swammerdam, Harvey,Malpighi).

On the otherhand, Leeuwenhoek and his followers (spermists or animaliculists, Leibnitz, Boerhave) [REF:63] believed in the concept that:
1. The mother serves only as an incubator for the homunculus.
2. All characteristics are inherited from the father.

Some periods from a letter to the Royal Society, March 1685, in which ,after a quotation by Nehemia Grevius [Grew the botanist] about Harvey and Reinier De Graaf, van Leeuwenhoek writes (see page 45 above):
"And I say that they (the physicians) are wrong, and that those are still mistaken, who claim that humans and animals arise from eggs, whereas not the male semen comes into the uterus, yes that this is more than anything else the most stupid thesis that is in vogue among physicians.

We know to day from embryology that neither the egg not the spermatozoon contains a complete or developped embryo (Epigenesis theory).
Only in course of the second half of the 19th century it was recognized that both the role of the ovary and the sperm are equivalent.
Notwithstanding the conceptual differences between Regnerus de Graaf and Antonie van Leeuwenhoek, they were advocates of the "evolution theory",just two centuries before Charles Darwin (1809-1882) and Ernst Haeckel (1834-1919), although this expression has a quite different connotation today.

A venomously pen-combat.

Both De Graaf and Jan Swammerdam did research on the human female uterus and ovaria. Earlier, Niels Stensen (Nicolaus Steno, 1638-1686) observed the follicles in an animal, the thorn-back. In 1668, de Graaf published the results of his research about the human follicles and wrote "Omne vivum ex ovo", following Harvey. However, the research had been issued earlier in a pamphlet (a socalled prodomus) by Johannes van Horne (1621-1670) of the University of Leiden. According to the Dutch historians Annie and Jan Romein [REF:69], Jan Swammerdam (a talented scientist, specialist in the anatomy of insects, though remarkable ambitious and suspicious) became so angry and embittered by this, that a long-standing and venomously pen-combat followed and he accused de Graaf of comitting plagiarism. The Royal Society was very embarassed with this. Antonie van Leeuwenhoek tried to sooth Swammerdam, to no purpose. In 1673, De Graaf died. It is said that Antonie van Leeuwenhoek blamed Jan Swammerdam for the untimely death of his friend de Graaf. Indeed, in 1673 the letters of Swammerdam became in a different strain, more generous. Probably, Swammerdam felt himself guilty. In the work "Erflaters der beschaving" Annie and Jan Romein mentioned that Herman Boerhave also has let himself on about this question [A. en J. Romein, (1940) REF:69] , [C.A.M.Jansen (2003) REF:83]

NOTE: Probably in consequence of the combat between de Graaf and Swammerdam, the discoveries of van Leeuwenhoek were send by De Braaf to the Royal Society (May 27th ,1673) in the same letter in which de Graaf complained about Swammerdam ! [REF: 88]

On several pages in his work van Leeuwenhoek, observing both the germination of plants as well as that of animals and their sexual organs, he inclined to a different concept: Especially when he observed twins, the offspring from the marriage between a white male and a colored woman, or the crossbreeding between a horse and a donkey, he had his doubts. In a letter to Leibnitz (XXX, Nov.17th,1716) van Leeuwenhoek mentioned that he imagined himself different kinds of spermcells : "males or females", dependent on their size and motility. (See : 4th cent. B.C. Hippocrates, On the Generating Seed and the Nature of the Child).

It is recognized that the female-bearing, oval-headed X-sperm [Gynesperm] are relatively bigger, slower and live much longer. They have far greater staying power against the hazards of the vaginal environment and they can survive up to 5-6 days.]

Van Leeuwenhoek even speculated about "placing a fertilized egg into the uterus of another female animal" to see the influence of the mother !

Missive March 30. Delft 1685. Study of the uterus of a dog.

uterus of a dog
"At position Q(upper left), I discovered a few little animals from the semen... From these observations we could see very clearly that it is not the vagina but the uterus (womb) which is created to receive the semen.."

"Thus, one should know that it is certain to me that the nutritious material from the mother can cause many changes in the animals". He could not prove it, but he made speculations about an essential, and imperceptible material in the seeds of trees (and the seeds of those trees that produced the observed seeds), in the spermcells as well as in the eggyolk that could influence the characteristics of the offspring. "De eerste wesentlijcke stoffe ofte begin", i.e. "The first essential material or the beginning, will be imperceptible and hidden to us".
In 1953, Watson and Crick described the structure of DNA, [REF:26].
The Essential and Imperceptible Matter
Essential material
Leeuwenhoek discovered spermcells in November 1677 and published his observations between 1678-1717. Before he was chosen as a member van Leeuwenhoek he wrote a letter to William Bounker of the Royal Society in Latin (Phil.Trans. Vol.XII,nbr. 142, 1678) in which he showed a picture of spermcells of the human and the dog. At the suggestion of the medical student Johan Ham at Leiden, Leeuwenhoek examined seminal fluid and observed spermatozoa.In 1677, Johan Ham, brought him a specimen ostensibly of semen in which Ham himself had found small animals with tails, which Leeuwenhoek now observed as well.
Ham brought him "the spontaneously discharged semen of a man who had lain with an unclean woman and was suffering from gonorrhea."
See: Leeuwenhoek's Perception of the Spermatozoa, [REF:72]. But, Ham, probably from Stettin (Germany) thought that these spermcells were not a normal part of the sperm [REF:18].

Leeuwenhoek resumed his own observations and in his own semen--acquired. He he observed a multitude of "animalcules," (at first he called them "Levende Dierkens") less than a millionth the size of a coarse grain of sand and with thin, undulating transparent tails. He draw the conclusion that the tails must be operated by means of muscles, tendons and joints. The scientist Lazaro Spallanzani (1729-1799) repeated van Leeuwenhoek's descriptions of infusoria and spermatozoa in 1776.
Van Leeuwenhoek estimated that 27,000,000 of these animalcules equaled a grain of sand, which seems minuscule compared with the germs in each egg.
Some scholars abusively think van Leeuwenhoek was convinced that man was preformed in them (the Homunculus) or that he thought they were human larvae, but van Leeuwenhoek only declared to observe muscles and nerves in those cells having a long tail. A long-running debate with the Harveian school started from that time on [REF:13]

No translation in Latin ! Missive 85, Delft Nov. 20th, 1694 to Petrus Rabus.
No latin translation

Antonie van Leeuwenhoek (see Missive 85) was not a supporter of a translation of his work about the reproduction and fertilization of women, into Latin, saying prophetically :

... I have shown my work to a very brilliant and distinguished Lord and I have said that you offered me to translate it into Latin to make it public....
However, it is his opinion, just as I am, that we should leave this... for fear that the world, being wicked and stupid enough, could use the knowledge of Natural History to bring ruin upon herself, and more and more could disrupt in dissoluteness.

Spermatozoa: Fast moving "little animaliculi" in semen, observed by van Leeuwenhoek.

Living little animals "diertgens",in the soft-roe or testiculi of a Codfish... 25 april 1679, Delft.
Letter to Nehemias Grew

Missive to Nehemias Grew

First image of Spermatozoa. This image is protected.
Swimming Spermcells (In the uterus of a Rabbit)
SpermcellsRabbit Spermcells

Van Leeuwenhoek realized himself that the observation of sperm was delicate matter and thus he wrotes:

"That what I am observing is just what nature, not by sinfully defiling myself, but as a natural consequence of conjugal coitus..."

Spermatozoa (Dutch = "zaaddiertjes") after an image published in Phil.Trans. XII,nov. 1678) : 1-4 Human, 5-8 Dog.

"Klagte van den Auteur over ´t verdraijen fijner redenen", Missive March 30th, 1685,pag.74
Leeuwenhoek complains about a misconception on spermcells, saying:

Complains by van Leeuwenhoek

"Recently a little book is fallen into my hands, named Collectanea Medico Physica, in which Capt. 5. Pag.8 among others is said: But the most strangiest story is, that the scholar mr. Cornelis Bontekoe told us (on good authority) from the curious Leeuwenhoek, that the human sperm is abundant of little infants and so on in the nature of things. Indeed, it is true that mister Bontekoe has visited me several times; However, I never have used such arguments to him, nor to anybody in the world, namely that human sperm is abundant of little infants: but I did say that there were plenty of living animals or verms in it, having long tails, and it is just that construction I showed in the figure." [ Note: Dr. Cornelius Decker of Amsterdam, also known as Dr. Cornelis Bontekoe (1647-1685), was one of the strongest advocates of tea drinking. He prescribed the consumption of eight to ten cups of tea a day, and claimed to drink 50 to 200 cups daily !]
Below: The titleplate of the main book of C.Bontekoe, 1684: "Korte Verhandeling van s´Menschen Leven.."

In a discourse about the semen of the Ram to Herman Boerhave (Missive Aug 26 th., 1717) van Leeuwenhoek concludes with the following:
["Ik weet wel dat ´er hooge schoolen fijn, die niet en gelooven, dat ´er levende Schepsels in de Mannelijke zaaden fijn; maar ik en ftoor my fulks niet, ik weet dat ik de waarheyt hebbe."]

Semen of the Ram
semen of the Ram

["I know very well that there are Universities who do not believe that living creatures are in the male semen; but I do not mind about this, as I know I have the truth."]

Missive to Boerhave

Missive to Herman Boerhave

In a letter (18 March and 31 march 1678) van Leeuwenhoek expressed the idea that in the sperm of the rabbit, vessels could be seen, [perhaps referring to the "principles" of the greek Empedokles of Acragas , circa 492-432 BC]. However in 1683 (on 22 jan. see below) van Leeuwenhoek strongly revokes this as being erroneous.

Spermcells and worldpopulation:
On another places (the missives 21 Febr.1679 and 25 Apr. 1679 to Nehemias Grew) Antonie van Leeuwenhoek estimated that the worldpopulation could be 13385 million, based on the spermcells in a Codfish and under the assumption that the world is as much crowded as in Holland, i.e. 1 million in the year 1679.

Other passages in the work of van Leeuwenhoek in which he gave his opinion about reproduction and fertilization:

Missive from Mar. 1678 :"Spawn and soft-roe of the fish are unified"
Missive from Jan. 1683 :"Reproduction of Frogs"
Missive from Jan. 1683 :"Looking for sperm of the cock in the yolk of a chicken-egg"
Missive from Jul. 1685 :"Of the beginning of the Plant and the Root in the seeds. The reproduction of the trees ´transposed´ to the reproduction of a human being", pages 1 - 30.


Animalcules, "Little animals"

Antonie van Leeuwenhoek´s first description of microbes:

Van Leeuwenhoek was the first to describe a number of microscopic aquatic life forms (Euglenids, Protozoa, Rotifers [REF:53], Foraminafera and others). He wrote: "We can easily conceive that in all rainwater which is collected from gutters and in all waters exposed to the air, animals may be found, for they may be carried thither by the particles of dust blown about by the winds."

In his letter of sept.7th, 1674 van Leeuwenhoek gives an accurate description of microbes for the first time in history.

When sailing on a boat in "het Berkelse Meer" he filled a bottle with water from the lake of Berkel and next day he observed it through his microscope, writing as follows:

"Passing just lately over this lake, . . . and examining this water next day, I found floating therein divers earthy particles, and some green streaks, spirally wound serpent-wise, and orderly arranged, after the manner of the copper or tin worms, which distillers use to cool their liquors as they distil over. The whole circumference of each of these streaks was about the thickness of a hair of one's head. . . all consisted of very small green globules joined together: and there were very many small green globules as well."

Here he describes the green charophyte alga Spirogyra a protozoa. In a letter of 1675 and a letter December 25th, 1702, he gives descriptions of Coelenterata and other protists, including a swimming bellshaped Ciliate, Vorticella (Dutch" ´t Klokkedyr") in rain-water, Hydra (the freshwater polyp), Volvox and Rotifers (Acoelomata, "Wheel animals" or "Radardiertjens").

Rotifer vulgaris, relaxed and contracted. Magnification X ca. 200 (woodcutting by W.H.Stam,1856)

Erroneously, Van Leeuwenhoek thought that the bulb at position b (see fig. A, at the left) was "the beating heart".

From: "Natural History of the Animal Kingdom". Jan van der Hoeven, Leiden. Editor G.T.N. Suringar, Leeuwarden, 1857. pp 179.

Prof.Dr.Jan van der Hoeven (1801-1868), zoologist and custodian of the Rijksmuseum of Natural History at Leiden, The Netherlands.

With respect to the latter, van Leeuwenhoek wrote his observations about this animal in a letter in 1702 (Philosophical transaction, N 295). However, it was Henry Baker [REF 80] who, after 50 years observed this animal (see image below) with a slightly improved version of the van Leeuwenhoek microscope (see also The Royal Society, 2002: " Resurrecting Van Leeuwenhoek's rotifers" [REF:84]).

Henry Baker´s observation of the Rotifers (1756)

Anthony van Leeuwenhoek also made reference to the group of Foraminafera. One of his drawings most likely is an Elphidium crispum a single cell organism, possessing a shell and pseudopodia to capture food from the water and found in sea weed on the beach at Scheveningen.

Bacteria in the Mouth

First image of Bacteria. This image is protected.
First image of Bacteria. No permission to copy this image
Dotted line between C and D indicates motility.

Van Leeuwenhoek´s famous description of microbes in tooth plaque (First edition, Delft in Holland, 12 September 1683, to Francois Aston, Pag.11). Leeuwenhoek´s drawing of short rods of bacilli and bacteria, the spheres of micrococci, and the corkscrew spirillum.

(1B. In DUTCH)
"Mijn gewoonte is des mergens myn tanden te vryven met zout, en dan myn mont te spoelen met water, en wanneer ik gegeten heb, veeltijts myn kiezen met een tandstoker te reinigen;.... Dat in de gezeide materie waren, veele zeer kleine dierkens, die haar zeer aardig beweegden. De grootste soort,was van Fig.A. dezelfve hadden een zeer starke beweginge, en schoten door het water,of speeksel, als een snoek door het water doet;deze waren meest doorgaans weinig in getal"

"In the morning I used to rub my teeth with salt and rinse my mouth with water and after eating to clean my molars with a toothpick.... I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort had a very strong and swift motion, and shot through the water like a pike does through the water; mostly these were of small numbers."

Actually he estimated more bacteria in one single drop than the number of inhabitants living in the Dutch Republic at that moment.

He also observed that Vinegar and Alcohol could kill some bacteria in the mouth.

Philosophical Transactions of the Royal Society of London, Vol. 14, May 20, 1684, no. 159, pages 568-574, 1 pl.
An abstract of a Letter from Antonie van Leeuwenhoek,Sep. 12, 1683. About Animals in the scrurf of the Teeth

The Spittle of an old Man that had lived soberly, had no Animals in it; But the substance upon & between his Teeth, had a great many living Creatures, swimming nimbler then I had hitherto seen.... The Spittle of another old man and a good fellow was like the former, but the Animals in the scurf of the teeth, were not all killed by the parties continual drinking Brandy, Wine, and Tobacco, for I found a few living Animals of the 3d. sort, and in the scurf between the Teeth I found many more small Animals of the 2 smallest sorts. I took in my mouth some very strong wine-Vinegar, and closing my Teeth, I gargled and rinsed them very well with the Vinegar, afterwards I washt them very well with fair water, but there were an innumerable quant'ty of Animals yet remaining in the scurf upon the Teeth, yet most in that between the Teeth, and very few Animals of the first sort A. I took a very little wine-Vinegar and mixt it with the water in which the scurf was dissolved, whereupon the Animals dyed presently. From hence I conclude, that the Vinegar with which I washt my Teeth, kill'd only those Animals which were on the outside of the scurf, but did not pass thro the whole substance of It. .. .

[NOTE:Check out the following link: http://ce.ecn.purdue.edu/~piwc/w3-history/leeuwenhoek/leeuwenhoek-1684.html

In the same letter of 12 september 1683 (page 17-18) van Leeuwenhoek wrotes:
(2A. In DUTCH)
"Ik heb verfcheyde Juffrouwen in myn huys gehad, die begeering waren de Aaltgens in den Afijn te fien, van dewelke enige foo een tegenheyd hadden, dat fy voornamen noyt Afyn the nuttigen. Maar als men nu in´toekomende fodanige lieden fal komen te feggen , datter meerder dieren inde vuyligheyt die aan de tanden inde mond van een menfch fyn, als´er menfchen in een gantfch Koninkryk leven, en voornamentlyk in die geene die haar mond niet en reynigen : .... waar door fo een ftank uyt veele haar mond komt, dat het verveelt datmen tegen haar spreekt , ´t welk by veele gefeyd werd een stinkende Adem te fyn, daar het inder daad meeft doorgaans een ftinkende mond is"

"I have had several gentlewomen in my house, who were keen on seeing the little eels in vinegar; but some of them were so disgusted at the spectacle, that they vowed they´d never use vinegar again. But what if one should tell such people in future that there are more animals living in the scrum on the teeth in a man´s mouth than there are men in a whole kingdom, and mainly in the mouth of those people that do not clean their mouth :..."

In his missive nr. 75, 1692 on page 510-511, van Leeuwenhoek declares :
(3A. In DUTCH)
"De Dierkens nu die aan de tanden en aan de voorste kiezen in de witte stoffe sitten, de hitte van de coffee niet konden verdragen, werden daardoor gedoot. Gelyk ik vele malen getoond hebbe, dat de dierkens die int water sijn, met een weinig hitte komen te sterven"

"The little animals sitting in the white stuff on the teeth and molars (the plaque), could not endure the heat of my coffee (drink) and they were killed. Like I have shown many times, that the little animals being in the water, died after some heating".

Evert Valk (in the year 1744, above mentioned) recognized and emphasized the importance of the observations of van Leeuwenhoek and he quotes the work of "Leeuwenhoek, De Vermaarde Man" (Leeuwenhoek, the Famous Man) in his publication " GENEES KUNDIG VERHAAL VAN DE ALGEMENE IN ZWANG GEGAAN HEBBENDE LOOP-ZIEKTE... ".

Evert Valk quotes van Leeuwenhoek (the missives 43, 59, 71, 75):

Giardia Lamblia
The parasite Giardia Lamblia, a Protozoa that could make cysts, causes several gastro-intestinal "stress" (Giardiasis, beaver feaver or back-packers diarrhea).
It seems likely that Giardiasis (infectious disease, caused by the entero-parasite Giardia Lamblia, acquired through contaminated or polluted water) was described first by Antonie van Leeuwenhoek in 1681, when he (being ill) examined his own diarrheal stool, saying that "his watery excrements do contain much more little animals (and different species) than a normal solid stool" [Dobell CA: The discovery of intestinal protozoa in man. Proc R Soc Med 13:1-15, 1920].

Either Microorganism (cocci) or scales of the human skin,Fig.H)
Microorganism in the gut,Fig.3, (probably Gardia Lamblia)

Protozoa and bacteria eating dead freshwater mussels ("ongeboore Veen-Moffelen, Veen-oesters") and small shell-fishes ("Schulp-viskens, schulp-dierkens") and playing a role in the purification of water.

In his missive nr. 96 to the elector of the Palatine (of the Rhine) Antonie van Leeuwenhoek reported that animalcules, both protozoa (rotating and motile animalcules with stalks and "clustered like grapes") and bacteria, were playing a part in the decomposition of dead mussels in the canals and fens of Holland - an early intimation of biological purification and recycling.
Van Leeuwenhoek also observed that Rotifers could live in colonies and survived desiccation in the form of resting eggs, or cysts, reanimating within 24 hours of coming into contact with water.

Size-estimation of Infusoria
Van Leeuwenhoek used the size of sand grains or musterd seeds as a unit of measurement.

"And this being so, we must say that according to the rules of geometry a barley-corn or mustard seed is a thousend-million times larger"..."thus we have reason to state that those very little animals are equipped with tails as well as limbs, mouth-parts and muscles, as the tails of Rats and Mouses ".
Size estimation

Chaos Infusoria:

The term "infusoria" comes from the practice of steeping substances (usually hay) in water by soaking at temperatures less than the boiling point. Originally, the name of the above mentioned species observed by van Leeuwenhoek in pepperwater, was "Chaos Infusoria" meaning in Dutch "Wardiertjes" (Animals of Confusion). During the 18th century scientists doubted whether this species was either a plant or an animal. See also the work of Linnaeus,(C.Linne, Dutch translation) : "Natuurlyke Historie of Uitvoerige Beschryving der Dieren,Planten en Mineralen [REF:79]

Yeast Globules

In MISSIVE June 14th, 1680 to Thomas Gale, Antonie van Leeuwenhoek describes "YEAST (GIST)"
using a hand made waxmodel of 6 globules. This might be the first time in history of biology an experimentalist uses a model to explain the reader !!”. Leeuwenhoek states that yeast was composed of tiny living things that were smaller than protozoa.


A Quasi Experimental Approach.

In the same letter of 1680 in which van Leeuwenhoek described the process of Beer-making and Yeast globules, he described (pages 7-10) one of the most remarkable experiments of his total Works (at least it appeares so to me, WAWM). On these pages he asked himself (1.) what the cause could be of airbubbles (LUGT-BELLETGENS) in beer and other materials, embedded in liquid, and (2.) ... "if it is true that no living creature could exist in a closed bottle". One should notice the modern style, perfectly formulated to falsificate a Null-hypothesis. Here the reader can take cognizance of his scientific approach as a pure researcher :

"Hiervan heb ik mede eenige preuven willen nemen, hebbende dan genomen twee glase tuben ABCDEFGHIKL.die na deselvige beyde onderaan AL waren toegemaakt ..."(see drawing on page 8).

Two Glass tubes,one sealed,one in contact with the open air

Experiment with glasstubes
[click to enlarge]

Quasi-Experimental approach of Van Leeuwenhoek with two glass-tubes, filled with clean rainwater at (BK-CI) and Pepper at (AL-BK). The bottoms A-L are sealed by heating the glasstubes. After heating and cooling, one tube (the Experimental) is sealed (at top G) and the other tube (the Control) is in contact with the open air (at top G). Both tubes are sealed at the bottom near AL. After cooling for about 15 minutes he filled the tubes with pepper and clean rain water. In spite of his expectations,van Leeuwenhoek observed a lot of organisms in the sealed tube after 5 days, while airbubbles still were escaping to the surface ! In this broth (water and peppers) he found that living creatures (protozoa) appeared. The finding could be explained in terms of the existence of anaerobic life. Thus, he came close to discovering anaerobes.

To some this might be a proof for the occurrence of the 'spontaneous generation', but van Leeuwenhoek rather suggests a different explanation for this phenomenon :
He mentions that within 24 hrs after the closed tube was opened much smaller little animals could be seen in this tube. Here he refers to other experiments in which it can be observed that verms or maggots (present in tainted meat) are developing from the eggs of flies, large enough to be seen. "Most likely Antonie van Leeuwenhoek suggests that the little animals in the tube produce a next generation of even smaller animals".
[van Leeuwenhoek describes the spores of Yeast, though it is not certain whether the existence of bacterial spores and their effect was known to van Leeuwenhoek. According to Brian Ford fungial spores (the truffle, Tuber spec.) are clearly resolved by the van Leeuwenhoek microscope-lense [REF:4]

Anyhow, it was 180 years before Louis Pasteur (- circa 1857-1876) did it (much more sophisticated) to explain the fermentation process and the physiological theory of Fermentation ! [REF:24]

Proving a hypothesis about the earth-movement.

Experiment Earth movement
[click to enlarge]

In the above remarkable Missive 101 (1696), written to Nicolaas Witsen (1641-1717), President Lord Mayor of Amsterdam, fellow member of the Royal Society, friend of Szar Peter the Great and a collector of "naturalia", Leeuwenhoek describes a (failed) experiment on the occasion of a dispute with Christian Huygens van Zuylichem (1629-1695), Dutch physicist and astronomer, (who discovered the Orion Nebula and Saturn's largest moon, Titan) to explain the earth-movement "Aertkloot" by the movement of clouds "de beweging der wolken".
[Christian Huygens, mathematician and astronomer, known for his work on the theories of centrifugal force, was called "The Great Sky-inquirer", "De groote Hemelbeschouwer", by Van Leeuwenhoek. In his work, Huygens was one of the pioneers of the so called "scientific revolution". Modern science was to a large degree established in the seventeenth century, and Huygens was one of the persons who brought this about.]
The experiment was done after "a complaint of a foreign professor that he has to recant his hypothesis about the earth-movement". Here an ingenious construction is build up : a glass-sphere (or bottle) within which a plumb-bullet ("the earth") is hanged. The movement of the clouds is imitated by pieces of sealing-wax inside. Nevertheless, "en passant" Leeuwenhoek describes the centrifugal force !

However, in the above experiment he does not take into account vacuum and the laws of gravity and mechanics, published in 1687 by Isaac Newton in his "Phylosofiae Naturalis Principa Mathematica".

Leeuwenhoek was the first to observe the constituents of blood.
Blood-corpuscles,erythrocytes [25,000 times smaller than a fine sand grain.]

This image is protected.
[click to enlarge]
Missive, March,3,1682,to Robert Hooke: Erythrocytes, Red bloodcells in the blood of a Salmon, containing "bubbles" and surrounded by a halo (this is a first description of the cell-nucleus).
"Want eenige fchenen my van binnen in een kleine fpatie beflooten te hebben,een rond bolletje of een globule, en een weinig fpatie van het bolletje, lag om het bolletje een heldere ring, en dan weder om den ring een langfaam fchaduwende omtrek, die de circumferentie van het ovaal maakte en die ick eenigfints met Fig.5 heb aangewefen."

Vascular system in lobated Braintissue of the pig

Antonie van Leeuwenhoek proved that venes and arteries are connected by capillary vessels (below, Fig.9). He calculated that the skin of an adult contains 2016000000 capillaries and that the heart makes 31536000 pulsations a year!


[click to enlarge]

Model of the closed bloodcirculatory system. Missive nr.67, April 1st, 1689,Delft.

Explaining this model (see image, fig.1), van Leeuwenhoek refers to the force on a fluid in a watercolumn described by the Dutch physicist and mathematician Simon Stevin(1548-1620), in "Beghinselen des Waterwichts".

Photo-negative.Branches of the vascular system, observed in the wing of a night-moth (Noctuidae, "Uyltje"). Missive 73. Delft June 24, 1692 to the Royal Society.
At the left. Fig. 1: ABCDEFGW = Main blood-vessel. X:X:X: = "membrane" of the small wing (see also S,T,V,W). Van Leeuwenhoek mentioned that he could not observe differences between arteries and venes.
At the right.Fig. 2,3,4: small fly (life-size) and its wing (enlarged), living in a sewer ("riool").

Wing Night-moth Vascular system

Most likely van Leeuwenhoek observed the wing of the species presented below: In Dutch it is called "Nacht-Uyltje".
[Handcoloured engraved lithograph 1830, from SEPP, J.C. Beschouwing der wonderen Gods, in de minst geachte schepzelen. Of Nederlandsche Insecten, naar hunne aanmerkelijke huishouding, verwonderlijke gedaante-wisseling en andere wetenswaardige bijzonderheden ... Amsterdam, J.C. Sepp, (1762-1860) ]

Transversal cut through the nerves of the Spinal Marrow of the Lamb.
Also showing the thick nerve-membrane (lateral cut) whithin which bundles of smaller neves can be seen.
Missive from May 26th, 1717 to his nephew, Medicine Doctor and Lector Anatomy, Abraham van Bleyswyck,Delft. This was one of the very last letters of van Leeuwenhoek (written at the age of 85).

Human Molar-tooth (Missive April 4th, 1687)
To observe the tooth van Leeuwenhoek took it from a Grave-digger, saying. "The little canals (cannon-bones) inside the tooth only can be observed by using very ´sharp-sighted´ magnifying glasses"

Human Tooth

Muscle fibers of a cow. "About 9-times smaller than my beard, containing about 5000 small musclefibers / Inch2"(Delft 3 March,1682 to Robert Hooke).
Transversal striation in muscles and muscle-fibers

[click to enlarge]

Flea (Pulex irritans)
Transmitter of parasites. (Missive 76, 1694) Van Leeuwenhoek´s treatise on the flea is a classic, proclaiming that fleas - like fish, dogs, and humans - are sexual beings.

When drawing this image, the limner ("Tekenaer") van Leeuwenhoek exclaimed :"My dear Goodness, what miracles are in such a little creature !".

Mosquito (Culex pipiens), larva and Snout-beetles (below)
Missive 64. Delft aug.24,1688: Biting mouth parts of the Mosquito
(according to van Leeuwenhoek the "stinging" parts are depicted after Jan Swammerdam).

"...Die ik den tekenaer naar het leven heb laten aftekenen..." - "Which I let the limner draw this from the life .."

On (at least) four different locations in his works, van Leeuwenhoek gives a description of (male and female) mosquito´s
: an early Missive (Jan.22, 1683 AD) directed to Christopher Wren, Missive 64 and Missive 77 (1688 AD) and the socalled missive XII (1713 AD), directed to the Royal Society. In fact he gives a description of three different species that could be found during his lifetime in the Lower Countries. Since Robert Koch (1882) mosquito´s are well-known as a vectorborne transmitter of diseases (malaria,yellow fever).

Mosquito. Stinging parts
[click to enlarge]

Green plant louse (probably Aphis ribes L) observed on the Ribes red-currant.
The louse is placed on his back onto the apex of a needle (see fig. EDUT).
Missive 90, Delft july 10th,1695 to Frederik Adriaan, Baron.

At position B van Leeuwenhoek saw a little drop of liquid that works "like a second magnifying glass because objects like houses and towers, can be observed upside down". Further he decribed the metamorphosis of the louse and Ants that "eat the louses" in wintertime.

[click to enlarge]

East Indian Centiped ("Duyzentbeen"), "Socalled burned paper fallen from heaven" (heavenly paper = dried Alga material or Scenedesmus) "Vlijm", Stinging Nettle, Amber [REF:4].
Centiped Nettles
[click to enlarge]

Insect "Flying creature with hardened redish-brown wing-shells" with larva,probably the Capricorn beetle.
Missive nr.99, Delft, March 6th, 1696 to the commander of the Dutch East Indies Company (VOC), Burgomaster of Amsterdam and member of the Royal Society London : Nicolaas Witsen. Note: The exact name of this insect was unknown to van Leeuwenhoek: ´Systema Naturae´ was published after the death of van Leeuwenhoek (see Carolus Linneaus, Holland, Leiden 1735).


Corn Weevil. Insect Coleoptera: Curculionidae: Sitophilus zeamais Motschulsky

Leeuwenhoek´s observations of corn weevils (maize weevils) mating helped to disprove the theory of abiogenesis. Before this discovery, people thought that the weevils were spontaneously generated from the grain itself and not from eggs. He also observed and described the life cycles of other animals [once thought to have been spontaneously generated out of materials such as mud and decaying matter].

Corn weevil

Different life stadia of the Ant

[Click to enlarge]

Silk-worm and Cocoon



Wood worm

Smallest fly
Observed on the blossom of a fruit-tree, enlarged. (The size of the image presented here is about 2-times the original etching !)

Smallest fly


In a Missive (1694) to the Royal Society, 16 september, Antonie van Leeuwenhoek describes the bloodcirculation in the hairy lag of a tiny crab. He could not observe any salt crystals in this blood.



Two Beetles (May bugs, Melontha vulgaris)
Species unknown to van Leeuwenhoek, he called them "Molenaars" (Mei kever).The beetle to the right drags the other beetle, laying on his back.(Missive, Nov.12th, 1680, page 47 to Robert Hooke).

Two beetles

Damselflies (Zygoptera) (Ischnura elegans, about 3-4 cm)

Missive, Nov.12th, 1680, page 48-49, to Robert Hooke. Two "Lampoons", Skimmers or Damselflies (Dutch "Libellen", "Jufferkens", "Schrijvertjes") in close contact. At the left: female with eggs. Photo-Negative.

"Komende dan op verfcheyde tijden in den morgen ftont, dat defelvige dierkens twee lang geftrekt aan malkanderen vaft fijnde vlogen, en ook foo neder gingen fitten, vliegende het manneken voor uyt, ..., te meer, om dat ik een opening op de rug van het wijfken vond, ende ten anderen om dat de eyeren in een grooten quantiteit bijeen lagen omtrent B"

Two lampoons


Filtersystem of Mussels (Molluscae)


The scales of the Eel

Antonie van Leeuwenhoek observed that,in contrast to the general opinion, the skin of an EEL is covered with scales, and refers to the commandment in Deuteronomy and Leviticus to the Jews not to eat fishes that do not have fins and scales
["geen vinnen en schobben", see microsopic view of the scale-structure at fig. 1 and eye-view at fig.2, Deuteronomy 14;10 and Leviticus 11;12].
Skin of the Eel

The vitreous body of the eye of a Cod-fish and the crystalline body

Tadpole - Frog metamorphosis Missive 65. 7 september 1688

Without any cell theory in which to place his results, Leeuwenhoek described
the eggs as to consisting initially of an inconceivable
number of rather complex globules in a watery fluid
Even the dissected body of a young free-swimming tadpole
seemed to be composed of globules alone, with no intestines,
nerves, or vessels.

"The shape of many of these eggs changed from day to day:
For,in stead of roundish, they became oblong. Little tails were formed.
And it apeared to me that I saw heads.
I opened many of these eggs,yes even on the seventh day
after the moment I took them in my home
and some "kikvorschen" (tadpoles) were developed so much
that the became motile.... The motion of the blood in these tadpoles exceeds all the rest of small animals and fish I have seen"

Missive nr. 65: Van leeuwenhoek describes the metamorphosis of the frogs (tadpoles, "kikvorschen" or "worken") from the egg (etching fig. 1 upper left corner). Van Leeuwenhoek wrote: "The fact that Harveus or Swammerdam did not see a head will be clear, because they did not use a magnifying glass"!

NOTE:This missive has been republished in:Opuscula Selecta Neerlandoricum De Arte Medica,Vol I,1907,pp 47-67.

Frog lifestadia
Tadpole metamorphosis
[Click to enlarge]

Missive nr 65 Swammerdam and Harvey (Harveus), dealing about the Tadpole

Tadpole. Missive to Swammerdam and harvey

Fluke, a parasite in the liver, Fasciola hepatica or "Leverbot" (by some others abusively called Planaria, a type of flatworm)

Missive from Bidloo

Passage from a letter of Govard Bidloo (Henrik van Kroonevelt Ed., 1698, page 27) a memoir to Antonie van Leeuwenhoek, about the animals which are sometimes found in the liver of sheep, on the etiology of diseases (the Plague) and referring to remarks of scientists abroad on his work, and quoting the quality of the Magnifying glass made by Benedict de Spinoza [52] .

Bird´s feather (Veer)

Bird Feather

Hair of a pig, cross section (1681)

Pig hair

Annual-rings and the structue of Wood (Northern-European and Tropical Trees)
These drawings are masterpieces !

Annual rings of wood

Different stadia of the Nutmeg (Myristica fragrans), Missive 88, May Ist,1695,"Van de Noote-Muscaat" to Antoni Heinsius,Raat Pensionaris van Holland, &c;"
In an earlier missive (1676), Van Leeuwenhoek had already noticed that a volatile constituent of nutmeg killed or repelled mites, [the essential oil appears to be the psychotropic substance myristicine].


Coffeeplant: Beans, Germ and Cellular-tissue


Wheat germ


Below: Germation of the seed of the cottontree (Malvaceae) a dicot, surrounded by a whitish film. Leeuwenhoek describes 4 leaves: two very small ones (seedcoat ?) and two very thick ones (cotyledons or seedleaves) and the primary root. The two thick and spotted cotyledons are spread out with tiny spikes (see figure 3). From: "Ontledingen en Ontdekkingen, Delft in Holland den 12 October 1685, pag. 34-36".



Leeuwenhoek also describes the spots in leaves : "I have depicted the leaves at such a magnitude that you can see the globules ("tiny spots of different size") that lay within them (Fig 3 A..H). Actually, there are much more of these spots than I could depict in the drawing ; they are much smaller and not given in the right proportion. After cutting the leaf, those thin globules showed the very beautiful lightgreen color my eyes have ever seen. Some of them were darkgreen and their color were the black color of wax alike. Fig. BE is the part of the stem and the radix within which only very few green globules could be observed".
Here undeniable, Van Leeuwenhoek describes chloroplasts (the little green Globules involved in Photosynthesis, [33]) positioned in the Mesophyllum of the leaves. The average chloroplast diameter is ranging from 3-6 micrometer (microns). Since Van Leeuwenhoek could reach magnification of X 300 to x 450 or more (2 microns or less),the size of magnified chloroplasts would be 0.9-1.8mm, which is indeed visible at this magnification: [1 micron = 0.001 mm]

In his letter (Delft,July 13th,1685, pag. 7-8), van Leeuwenhoek gives a model of the position of these small globules in leaves (presumably of a maple, see Fig.5 below) arranged within "membranes" (= probably van Leeuwenhoek meant the ribs or nerves of the leaf). “Green-leaf”: the greek words are chloro-phyllon.

Green globules

Note: Pierre Joseph Pelletier (1788 - 1842) a French chemist, isolated the blue-green hydrophobic and waxy compound chlorophyll in 1817.[25]

Missive to Herman Boerhave, Sept. 28th, 1716
Parts of a broken Coconut from Curacao "Kurasschouw":
The seed,the freshly coconut meat and structural-details.

Coconut "Defe foogenaamde Cocos-boom feyt men dat het nuttigste gewas voor het Menfelyk geflagt is.."

Coconut, germinating plant inside the seed, true size

"This socalled Coconut tree is, it is said, the most useful crop for mankind".

Matured seed of the Cottontree

Crystals- in Wine-Vinegar (A..H) and the Vinegar-eel (LM-NO).
In 1695 Antoni van Leeuwenhoek observed, under the microscope that different forms of crystals grow from the solutions of different salts.

(Most likely at D: yeastcells.)

Crystals in Vinegar
Crystals in Vinegar

Calcium-Carbonate Crystals
Carbonate Crystals

Pareira bravea, Curare

Van Leeuwenhoek, in his missive from 1717 to the Royal Society gives a description of the Salt-Crystalls, observed in the Homoeopathic Herb : PAREIRA BRAVA, ("Geneeswortel", Virgin-vine or CHONDRODENDRON TOMENTOSUM i.e. CURARE ! a febrifuge and muscle-relaxant poison), useful in renal colic, prostatic affections, and catarrh of bladder.The medicine is prepared from the root of Chondrodendron Tomentosum, a climbing shrub of South America. The root contains alcaloids with antispasmodic and curarizing properties used by the Akawai Indians of Dutch-Surinam and it drawed the attention of the Medical world.

Missive from July 6th, 1717, (page 378-379) directed to "Cinck, Narrez and Rega, Professors at the Academy of Leuven".

Van Leeuwenhoek did not want to take medication at high age, but he complained about some pain at his short ribs and tightness of the chest. He was very suspicious about a medicine a certain doctor tried to give him, saying that it was just Salpeter. Van Leeuwenhoek refused to take it first but then he took it, declaring that he became sleepy of it. Later, this doctor confessed that a little opium was administered to the medicine. "Ik hebbe meermalen voorgenomen, wanneer ik quam ziek te worden, geen Medicinen te gebruyken, en alfoo in myn feer hooge jaren te fterven. Zeker Doctor Medicine, aan de welken ik klaagde over pynen die ik ontrent de korte ribben aan de regter zyde hadde (see above, Myonuclonus respiratorius), ende onder andere van benautheyt in ´t adem halen, dat eenige dagen duurde, verzogt my yets te geven, dat ik meer malen weygerde. Deze Doctor my doorgaans, als by my quam, verzoekende om my wat in te geven, zeyde eyndelyk dat het niet anders zoude wezen als Salpeter, ende dat ik de Salpeter wel was kennende; ´t geen ik hem eyndelyk toe stont, om dat ik zeer veel lof van de Salpeter hadde gelezen; ende de Salpeter niet alleen veelmalen door het Vergroot glas hadde beschouwt ; maar ook veelmalen dezelve, in ´t scheyden en smelten van mineralen, hadde gebruykt. Dit Sout, zoo veel men oordeelde dat ik tegelyk most innemen, zyn werkinge gedaan hebbende, ende den Doctor by my komende, zeyde ik tot den zelven, dat het geen simple Salpeter was;... ; waar op my geantwoort wierde, dat hy maar een half aasje Opium onder het Sout vermengt hadde."

"The last Missives"
In his last Missive from 17 sept 1717, just one month before he became 86 years, van Leeuwenhoek wrote to the Royal Society that "because his hands were too weak and a little trembling, he had to end his observations. His last words were much thanks to the Royal Society and for receiving a certificate ("Diploma") from the Society. Notwithstanding this, just 12 hours before he died (at nearly 91) he wrote two more letters to the Society ! His friend Johannes Hoogvliet (physician at Delft) translated these letters into Latin and send them to James Jurin, the secretary of the Royal Society at that time. In this missive (1723), van Leeuwenhoek describes his disease (Myonuclonus respiratorius) so precisely, that it is called the Leeuwenhoek disease.

Last Missive 17 sept 1717

The Leeuwenhoek signature and his daugther Maria (below) is from a book issued by the Delft historical society Delfia Batavorum: Facetten van Delft, Gedenkboek van het Genootschap Delfia Batavorum 1935-1985, H.K.L. Houtzager, red. [55]


Famous visitors at van Leeuwenhoek´s home

During 50 years van Leeuwenhoek wrote his letters (in Dutch), to the Royal Society in Londen as a member since 1679. Robert Hooke and Hendrik Oldenburg were the secretaries. Numerous famous and historical personages visited his works at his home : amoung these Christiaan Huygens, Boerhave, Heinsius, Descartes, Leibnitz (staying at Spinoza´s home at The Hague), Spinoza, Christopher Wren, Tsar Peter the Great who sailed on the "Delftse Schie" in good company with Antonie van Leeuwenhoek himself, Queen Mary (Mary Stuart II, wife of William III of Orange) and Queen An of Great Brittain,the prince of Lichtenstein and Frederik the Great. He dedicated a missive from 1717 to the Emperor Charles of Spain who could not visit van Leeuwenhoek due to a strong Eastern Storm. Another Monarch of that time-period who never visited van Antonie van Leeuwenhoek was Louis XIV, the envious "sun-king", plagued with various parasites, due to poor hygiene.
Many visitors complained about headache while looking through his microscope (with exception of van Leeuwenhoek himself who had extremely sharp visual powers).

Leibnitz´ Quotation about van Leeuwenhoek:
As a mathematician Leibniz claims (with Newton) the distinction of having invented (in 1675) differential calculus. As a scientist he appreciated and encharged the use of observation and experiment: "I prefer," he said, "a Leeuwenhoek who tells me what he sees to a Cartesian who tells me what he thinks."

NOTE: Leibnitz, who visited van Leeuwenhoek, corresponded with the secretary of the Royal Society Henry Oldenburg between 1661-1676 and he visited Spinoza in The Hague in 1675.


Letters (Missives or Sentbrieven) by Antonie van Leeuwenhoek

The first letter of van Leeuwenhoek, edited and translated by Regnerus (Reinier) de Graaf, 28 april 1673, is not lost [REF:75], it has been published in Phil.Trans.Vol. VIII,No 94,pp 6037-6038. The title of this work was: "A specimen of some observations made by a Microscope contrived by Mr. Leeuwenhoek, lately communicated by Dr.Regnerus de Graaf".
Since 1680 his letters (starting at letter 28 !) were edited by - Cornelis Boutesteyn, "Onsigtbare Verborgenheden","Ontledingen en Ontdekkingen" Leiden,- Henrik van Croonevelt "Vijfde vervolg der Brieven" Delft,- Adriaan Beman "Send Brieven" Delft - and - Daniel van Gaasbeeck "Ondervindingen en Beschouwingen Der onsigtbare geschapene waarheden, Vervat in verscheydene Brieven, geschreven aan de Wijt-beroemde Koninklijke Societeit in Engeland.", (Amsterdam ?),Leiden 1684.
Most of his works has been translated in English- and Latin and some in French. Leeuwenhoek's works, 'Ontdeckte onsigtbaarheeden´ which can be said to be the starting place for protozoology, bacteriology, and microbiology was published mainly in a series of 375 letters addressed to Robert Hooke or to his successors at the Royal Society.

The first letters, written in Dutch, begin with number 28. This collection has an engraved title, reading 'Ontdeckte onsigtbaarheeden´ door A. van Leeuwenhoek' and was presumably issued in 1695.

NOTE: At the time of van Leeuwenhoek in England the old style of chronology was still in use,by which the year began on March 25. The new or Gregorian style was adopted in England in September 1752 !

Clifford Dobell, who spent his working life studying the protozoa and his spare time researching the life and times of "the father of microscopy" has given a detailed biography of Antonie van Leeuwenhoek and edited his work in 1932, [4] The constituent parts, with Dobell numbers, are as follows: 1. Letters 28-31; Leiden 1686; D8 2. Letters 32-33; Delft 1694; variant unknown to Dobell 3. Letters 34-36; Leiden 1686; D8 4. Letter 37; Leiden 1684; D2 5. Letter 38; Leiden 1691; D5a (unseen by Dobell) 6. Letter 39; similar but not identical to D2, paginated 11-28 7. Letter 40; Leiden 1683; D3 8. Letter 41; Leiden 1684; D4 9. Letters 42-43; Leiden 1691; D5a (unseen by Dobell) 10. Letters 44-45; Leiden 1685; D6 11. Letters 46-47; Leiden 1685; D7 12. Letters 48-52; Leiden 1686; D9. Nordenskiold, pp. 164-66; Printing and the Mind of Man 166; Garrison & Morton 67.

Two collections of his works appeared during his life, one in Dutch (1685-1718) and the other in Latin (1715-22); a selection has been translated by S. Hoole, The Select Works of A. van Leeuwenhoek (1798-1807).
The first editions, first issues (apart from one in second issue), and the complete set of Leeuwenhoek's letters, are very rare, and first appeared in the original Dutch. Leeuwenhoek’s letters sparkle with the excitement of discovery. Part of the fun of reading them is catching his infectious joy; where words like astonished, wonderful, odd, perfect, marvelous, inconceivable are frequent as he describes his “wee animalcules” and their motions.
To (Dutch) readers nowadays, these publications are very amusing. Here is a man who writes directly, "playing upon words" with great verbosity [43].
John Chamberlayne (251, 255, and 256) translated some letters of Van Leeuwenhoek for the Royal Society [REF:77]. It is a pity that much of the Dutch idiom used by van Leeuwenhoek is lost in the English translation (see "Anton van Leeuwenhoek Selected Works", translated by Samuel Hoole ± 1800).
One title-plate is an etching of the wellknown painter and etcher Romein de Hooghe (Romyn d´Hooghe) a good friend of van Leeuwenhoek. Two other title-plates are signed by J.Goeree and van Schaak.

The assumption is made that he was not a skilful drawer. However, it is difficult to imagine a man, carefully looking through a microscope holding it with one hand and making drawings at the same time. It is not certain who made the drawings published in his works. As van Leeuwenhoek lived almost a century, there must have been several artists working for him. According to C.C.Dobell he employed the aid of artists to convert his crude observational sketches into usable illustrations for the Royal Society. These artists remain unknown but Dobell, the biographer of Leeuwenhoek, mentions Johannes Vermeer as a candidate (though unlikely).
Some of the illustrations have been attributed to Willem van der Wilt (1691 of 1692 - 1727) and / or his father Thomas van der Wilt (1659-1733) a popular Delft Portraitist [[31].


Poem on this titleplate
Poem Thomas vd Wilt

A poem by Thomas van der Wilt
From "Send-Brieven"... over het WONDERLYK GESTEL van De Vefelen der Spieren..,
Ed. Adriaan Beman,Delft 1718, titleplate.

Many of his observations were summarized in 1696 , "Arcana naturae detecta". Most of his work is published in the "Philosophical Transactions" of the Royal Society in London and about 27 missives were published in "Memoirs of the Paris Academy of Sciences". During his life a collection of his work was published twice : in Dutch language (1685-1718) and thereafter in Latin (1715-22). Part of this work was translated by S. Hoole, "The Select Works of A. van Leeuwenhoek (1798-1807)" . Just 12 hours before he died he wrote two letters to the Royal Society.


The year 1632
Van Leeuwenhoek,Vermeer,de Spinoza,Galileo

1632 is an important year in the cultural history of the Netherlands.

Johannes Vermeer,the painter, was born in Delft in 1632 in the same week as van Leeuwenhoek.

It is said that Johannes Vermeer was a good friend of van Leeuwenhoek. Both are mentioned on the same page of the municipal records in the city of Delft. Nevertheless, not any official document can state this friendship. But, it is true, van Leeuwenhoek was the testamentory executor of Vermeer. This fact is mentioned in a document from the late Abraham Bredius (who made up the Catalogue of the Rijksmuseum at Amsterdam) and one of the best connoisseurs and art-historicians in the Netherlands (see below).
It is also suggested that van Leeuwenhoek was a model for Vermeer´s paintings the Geographer and the Astronomer. Hajo Dutching [REF:30] made the suggestion that van Leeuwenhoek possibly charged Vermeer to paint these works. Anyhow, both had a passion for optics and the properties of light. Further it is mentioned that, on a suggestion of van Leeuwenhoek, Vermeer used a camera Obscura for bringing in details in his paintings (see the book: Vermeer's Camera: Uncovering the Truth Behind the Masterpieces ,Philip Steadman,Oxford University Press, Incorporated 2002). The father of Vermeer was a textile merchant in Delft, as was the father-in-law of van Leeuwenhoek.

In a document (see Abraham Bredius: "Iets over Johannes Vermeer",Oud Holland, 3. page 217 (1885) van Leeuwenhoek is mentioned as the testamentary executor of Catharina Bolnes, the widow of Johannes Vermeer.
[REF:29], Quoted from : Delft, prot. not. Floris van de Werff, 1 Febr. 1678.

" 1 Febr. 1678, compareert Anthonij Leeuwenhoeck, te Delft, als bij de Heeren Scheepenen der stadt Delft, gestelde curateur over den insolventen en gerepudieerden boedel en goederen van Catharina Bolnes,Wed. en boedelhoudster geweest van wijlen Johanes Vermeer,in sijn leven schilder binner desert Stadt en verclaerde machtich te maeken.."

The Geographer (Leeuwenhoek, "possibly as a Model" in Vermeer´s Painting)

Vermeer The Geographer

In November 24,1632 exactly four weeks after the birth of van Leeuwenhoek and Vermeer, Baruch (Benedict) de Spinoza, a great admirer of van Leeuwenhoek, was born in Amsterdam. Spinoza, living at Amsterdam up to 1666, learned how to grind lenses in 1656, the year he was banished from the Synagogue. He was a great philosopher and a well-known lense-grinder too, and there must be some exchanges in knowledge about optics between them [REF:52].

In 1632, Rembrandt Harmenszoon van Rijn painted "Doctor Nicolaes Tulp's Demonstration of the Anatomy of the Arm" and "The Raising of Lazarus" (etch).

In 1632 Frederik Hendrik, Prince of Orange, nicknamed "the fortress compeller (stedendwinger)", defeated the Spanish at Maastricht (eighty-years War) and from that time on a period of wealth, stability and religious toleration started in The Netherlands.

In 1632 the Durch Reformed Church and the Athenaeum Illustre (precursor of the University of Amsterdam) were founded.

In 1632 the United Dutch East Indian Company (VOC) reached maximum worldpower.

In 1632 Galileo Gallilei published his most important work, "Dialogo sopra i due sistemi del mondo" , (´Samenspraak over de twee wereldstelsels').
[Free-fall with uniform acceleration: It is worth noting that Simon Stevin observed that objects having different masses all underwent equal (uniform) fall-acceleration, three years before Galileo Galilei published his concept of the Heliocentric World, [REF 64].

On August 1632, John Locke was born at Wrington, a village in Somerset.

1632, the third wave of the Bubonic Plague (Black Death) reaches Europe.

Van Leeuwenhoek: Entrance Kluyver Laboratory for Biotechnology, University of Technology, Delft.
Van Leeuwenhoek Kluyer Laboratory Delft


Concluding Remark:

Antoni van Leeuwenhoek: perhaps he was an amateur in Science, but his perceptive faculty and his honesty was unsurpassable.


[1] History of the Light Microscope,1995, 1997 Thomas E. Jones.

[2] Virtual Microscopy

[3] Antonie van Leeuwenhoek:Detailed Biography by Top Telemedia Ltd., India Biographies,2002


[5] Antonie van Leeuwenhoek:Short Biography. PageWise Inc. 2001. Biography of Antony van Leeuwenhoek, discoverer of microbes and the first to describe spermatozoa

[6] Antonie van Leeuwenhoek Spermatozoa.E. G. Ruestow, J. History of Biology 16: 185-224.

[7] van Leeuwenhoek First Microscope. History of the Lightmicroscope Science Medical Antique Collections.

[8] University of California Museum of Paleontology

[9] Botany on line Microscopy English edition. Peter v. Sengbusch,2002

[10] Botany on line Microscopy German edition. Peter v. Sengbusch,2002

[11] Biography Antonio van Leeuwenhoek. Whonamedit.com Biographical dictionary of medical eponyms

[12] Museum Boerhave Bibliotheek, Lange St. Agnietenstraat 10 2312 WC Leiden (With references to other van Leeuwenhoek websites and Articles).

[13] Leeuwenhoek´s Perception of the Spermatozoa, Adapted from an article by E. G. Ruestow, J. History of Biology 16: 185-224. [Website contains many Citations from van Leeuwenhoeks Letters]

[14] John Postgate: A historical account of the life and work of the Dutch Microbiologist Antoni van Leeuwenhoek.

[15] Museum of Microscopy: © 1998-2002 by Michael W. Davidson, Mortimer Abramowitz, Olympus America Inc., and The Florida State University.

[16] Antonie van Leeuwenhoek "Ontdeckte onsichtbaarheeden", Original Bands 1685-1717 (Leyden and Delft).

[17]C. Dobell, "Anthony van Leeuwenhoek and his "Little Animals", (London: Staples Press, 1932).

[18]A. Schierbeek, Antoni van Leeuwenhoek. "Zijn leven en zijn werken", 2 vols. (Lochem, 1950-51).

[19] Prof. Dr. A. Charlotte Ruys (1957),"Leerboek der microbiologie en immunologie", NV Oosthoek Utrecht.

[20] A. Schierbeek, Measuring the Invisible World. " The Life and Works of Antoni van Leeuwenhoek" FRS, (London, 1959).

[21] Gerald L´Estrange Turner (1981), "Historische microscopen", Studio Vista (Cassell ltd),London,Christies Collections.

[22] Kluwer : Antonie Van Leeuwenhoek; Journal of Microbiology and Serology

[23] P.Smit on page 9-23, De Ontdekking van de "Kleijne diertgens" in F.Wensinck (1976) "De microbiologie drie eeuwen na Antonie van Leeuwenhoek", Centrum voor Landbouwpublicaties en landbouwdocumentatie",Ed. Pudoc, Wageningen.

[24] L.Pasteur, (1862) "Die in der Atmosphare vorhandenen organisirten Korperchen,Prufung der Lehre der Urzeugung" in Annales de Chimie et de Physique, 3.Serie Bd . LXIV.

[25] Pelletier, P. J. and Caventou, J. B. (1818). Ann. Chim. et Phys. 9: 194-196. See also in : "What does the green mean ?"

[26] Watson and Crick described the structure of DNA in 1953.

[27] Jeff Miller: UCSF Research Philosophy Of Science, Scientists and UCSF, October 22, 2001.

[28] LEDERMÜLLER, M.F.(1758),"Versuch zu einer grundlichen Vertheidigung derer Saamenthiergen", Nuremberg, G.P. Monath.

[29] Abraham Bredius: "Iets over Johannes Vermeer",Oud Holland, 3. page 217 (1885).The Art Collection of the Bredius Museum, The Hague.

[30] Hajo Dutching "Jan Vermeer van Delft" Rebo productions, Ed. Koninklijke Smeets Offset, bv. Weert, (1996).

[31] Website: Willem and Thomas van de Wilt http://www.xs4all.nl/~kalden/dart/d-a-verkolje.htm

[32] Website: Allan Shin:To Make a Van Leeuwenhoek Microscope Replica http://www.mindspring.com/~alshinn/Leeuwenhoekplans.html

[33] Website: W.A.W. Moll, Electron Microscope and Cellbiology : studies on Chloroplast-membranes (2002) http://www.euronet.nl/users/warnar/chloroplast.html

[34] Cittert, P.H. van. "Descriptive catalogue of the collection of microscopes in charge of the Utrecht University Museum", Noordhoff, Groningen (1934).

[35] Bjorn Uwe Kambeck, Antique microscopes and other scientific instruments and books, 2002

[36] Interactive Historical Timelines: Who What When :Historical Timelines, SBROWNING.COM

[37] Prof.dr. J.C. van Lenteren: Did Antonie van Leeuwenhoek discover insect parasitism ?ANTONIE VAN LEEUWENHOEK SYMPOSIUM, 1- 6 October 2000, Haarlem, The Netherlands.

[38] Groen van Prinsterer, G. "Handboek der Geschiedenis van het Vaderland" (van Leeuwenhoek, uitvinder van de mikroskoop). Ed. H. Höveker, Amsterdam (1852), pag 382.

[39] Spectacles: Mr. C.N.Chua BMed Sci. MRCP FRCOphth Oxford Eye HospitalOphtalmology

[40] A brief history of toxins(2002). Alistair Lax King's College London

[41] Antonie van Leeuwenhoek, Microscopical observations. The Educational Broadcasting Corporation (2002).

[42] The Slow Death of the Spontaneous Generation. The National Health Museum (2002).BIOTECH


[44] Van Hogenhouck Genealogy

[45] Pieter Harting. "De nieuwste verbeteringen van het MIKROSKOOP en zijn gebruik, sedert 1850". H.C.A.Campagne,Ed. Tiel, 1858.

[46] Dr. P.W. van Cittert "Het Microscoop", J.Noorduijn en zoon, N.V., Gorinchem 1943,Nederland. Noorduijn´s Wetenschappelijke Reeks.

[47] Virtuellen Museum der Wissenschaft :Vortrag Kurt Paulus "Das Mikroskop Werkzeug des Lebenswissenschaftlers", Berlin 2001

[48] Jan van der Stroom "Life is wonderful", http://www.geocities.com/levensverhaal/index.html

[49] MEYER, Klaus, Geheimnisse des Antoni van Leeuwenhoek. Ein Beitrag zur Frühgeschichte der Mikroskopie (Lengerich etc., Pabst Science Publishers, 1998). 647 pages. ISBN 3-931660-89-3. See web site: Mathias Orgeldinger. Vorreiter der wissenschaftlichen Mikroskopie (2000).

[50] Giorgio Carboni, (1996): A GLASS-SPHERE MICROSCOPE

[51] Zanot Science Lessons : Studying Cells Tutorial

[52] "Cells of Spinoza": Tetsuro Onuma, Representative of Yone Production Co.Ltd. (2002)

[53] World of Rotifers:Richard L. Howey and Wim van Egmond (1999-2002)

[54] Blok, P.J. "Geschiedenis van het Nederlandsche Volk", part V. Ed J.B.Wolters, Groningen , 1902

[55] Kaldenbach Website : Leeuwenhoek Signature

[56] KNAW : Royal Netherlands Academy of Arts and Sciences

[57] Palm, L.C. Antonie van Leeuwenhoek (1632-1723), De onsigbare geschapene waarheden, in:Van Stevin tot Lorentz, Intermmediaire Bibliotheek, A.J.Kox, M.Cjamalaun, Eds,(1980), ISBN: 90 6434009 9

[58] Hooykaas, R. 'Science and Religion in the 17th Century: Isaac Beeckman (1588-1637).' Free University Quarterly [Amsterdam] 1 (1951): 169-183.

[59] The Galileo Project Development Team. Richard S. Westfall Department of History and Philosophy of Science

[60] E.J.Dijksterhuis, ("The Mechanization of the World Picture: Pythagoras to Newton"), De mechanisering van het Wereldbeeld,Ed. Meulenhoff, Amsterdam, (1950), ISBN 90 290 0330 8

[61] Bertrand Russel, ("History of Western Philosophy"), Geschiedenis der Westerse Filosofie. Ed. Servire BV Katwijk aan Zee, (1948), ISBN 90 6077 307 1

[62] Christiaan Huygens Huygens: the greatest mechanist of the seventeenth century
[63] Schierbeek, A. ("Opkomst en bloei der Evolutieleer"), Haarlem, Erven Bohn, N.V., 1961.
[64] University of Utrecht: Library Gerrit Moll (1785-1838), Professor of Mathematics, Physics and Astronomy, and Director of the Utrecht Observatory. Andreas Cellarius, Harmonia macrocosmica.

[65] Peter Highes 2002: About Michael Servetus (1509 or 1511-1553)
[66] Dr. A.W. Moll : "About Jan Swammerdam and Antonie van Leeuwenhoek", University of Amsterdam (Amsterdam 1938)

[67] Konemann Verslaggesellschaft mbH,2000:"Islam Kunst und Architektur" (ISLAM,Art and Architecture), ISBN 3-8290-2557-2

[68] Source: Catalog Files Website Galileo Project: Desciption Antonie van Leeuwenhoek.
[69] Annie and Jan Romein : "Erflaters van onzer Beschaving", Ed. Querido, 1940,Amsterdam, pp 18-21.

[70] UBA: De Nederlandse Leeuw. Een gids voor biografische gegevens van Nederlanders : Universiteitsbibliotheek, Singel 425, Amsterdam (Biographic data, Library of the University of Amsterdam)

[71] Description of Cornelis Drebbel in: Jacques Alexandre de Chalmot (1734-1801), "Biographisch Woordenboek der Nederlanden", Vol.VIII, pp 348-351,Ed. Johannes Allart, 1798-1800, Amsterdam [extremely rare book].

[72] Leeuwenhoek's Perception of the Spermatozoa: E. G. Ruestow, J. History of Biology 16: 185-224.
[73] LEEUWENHOEK, ANTONI VAN (1632-1723). - The collected letters of Antoni van Leeuwenhoek; Alle de Brieven van Antoni van Leeuwenhoek, 10 vol. Ed: Lisse, Swets & Zeitlinger, 1939 - 1979 (scientific commentary).

[74] Kuhn, Thomas S. 1973 [1962]. The Structure of Scientific Revolutions. Chicago : University of Chicago Press.

[75] Clifford Dobell, F.R.S. (London) "The first 27 unpublished letters of Antony van Leeuwenhoek", has been published in : Opuscula Selecta Neerlandicorum De Arte Media, Fasciculus Nonus, Nederlands Tijdschrift voor Geneeskunde, Amstelodami Sumptibus Societas, MCMXXX (1930). In this work the following letters are published for the first time, in their entirety: 3a,6a,7,9,10,11,13,13a,14,16,17,18a,21a, and 26.

[76] Mr. J.van Lennep, Prof. W.Moll and J.Ter Gouw : "Nederlands Geschiedenis en Volksleven", A.W.Sijthoff Ed., Leiden, 1878, Vol.II,pp 207.

[77] L.C. Palm :
" The Collected Letters of Antoni van Leeuwenhoek Part XV (1704 - 1707) ",Swets & Zeitlinger ISBN 90 265 1548 0

[78] Quintus Septimius Florens Tertullianus, "Opera ad Vetustissimorum Exemplarium, Novatiani Tractatus De Trinitate", Lutetiae Parisiorum, MCDLXXV (1675), pp 705-730.

[79] Linneaus, C: "Natuurlyke Historie of Uitvoerige Beschryving der Dieren,Planten en Mineralen volgens het Samenstel van de Heer LINNAEUS", Part XVIII,"Beschryving van ´t Geslagt der Wardiertjes,waar mede het rijk der dieren beslooten wordt", pp. 193-204, Erven van F.Houttuyn,Amsterdam, MDCCLXXIII.

[80] Henri Baker: "Nuttig gebruik van het Mikroskoop". Lid van de Koninklijke Societeit en het genootschap van Oudheid onderzoekers te Leiden. ED: F.Houttuyn, Amsterdam, 1756.

[81] Jan Mol and the first van Leeuwenhoek film in :Biographisch Woordenboek van Nederland, Vol.V, 2001, page 351-353, Instituut voor Nederlandse Geschiedenis,Den Haag.

[82] A.Schierbeek, "Antonie van leeuwenhoek",ED. Kruseman Den Haag, 1963.

[83] Jansen, C.A.M. De tragiek in het leven van Reinier de Graaf. Tijdschrift voor Fertiliteitsonderzoek 2003; 17: 73- 8

[84] Resurrecting Van Leeuwenhoek's rotifers: a reappraisal of the role of disaccharides in anhydrobiosis [Review] Author(s): Tunnacliffe and Lapinski Source: Philosophical Transactions: Biological Sciences DOI: 10.1098/rstb.2002.1214 Publisher: The Royal Society


[86] The Christiaan Huygens WEB :http://www.phys.uu.nl/~huygens/

[87] The Musschenbroek microscope, Virtual Museum

[88] Nieuw Nederlandsch Biografisch Woordenboek, A.W. Sijthoff,Leiden, 1924, vol.VI, page 923.

[89] Griendel, Johann Fransica, Nuernberg, 1687

Scientific Collections: Dr. W.A.W.Moll, University of Amsterdam,The Netherlands.

Institute for History and Foundations of Mathematical and the Natural Sciences, Utrecht


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*) From the anthropological point of view it is (perhaps) more correct to say that humans lost their naivety on the very moment they realized themselves how to make and use innovating tools.