antony van leeuwenhoekl: tercentenary of his discovery of

BACTERIOLOGICAL REVIEWS, June 1976, p. 260-269Copyright © 1976 American Society for Microbiology

Vol. 40, No. 2Printed in U.S.A.

Antony van Leeuwenhoekl: Tercentenary of His Discovery ofBacteriaJ. R. PORTER

Department of Microbiology, College of Medicine, University ofIowa, Iowa City, Iowa 52242

INTRODUCTION ............................................................. 260LEEUWENHOEK'S MICROSCOPES........................................... 261DISCOVERY OF BACTERIA AND OTHER MICROORGANISMS ....... ........ 265LEEUWENHOEK THE MAN .................................................. 266LITERATURE CITED .................................................... 268

INTRODUCTIONThree hundred years ago Anthony van Leeu-

wenhoek (Fig. 1) wrote some of the most re-markable and significant communications inall scientific literature. According to Dobell (6),about 200 letters and manuscripts were ad-dressed to the Royal Society of London, and toother notable organizations and people. Severalof the more important of these communicationsdeal with the discovery of microorganisms, es-pecially bacteria, in 1676.

Besides the documents in the Royal Society'sarchives, a few are preserved in the UniversityLibrary at Leiden, the Municipal Museum atThe Hague, the National Library in Florence,and in the Leibniz Collection at Hanover. SinceLeeuwenhoek was proficient only in his nativelanguage, all his original correspondence wasin Dutch. However, many of his letters weredelivered after being transcribed into Latin,and some have been translated into English orother languages and so published.Leeuwenhoek's letters usually told of new

discoveries, often in entirely different fields.His wide-ranging investigations and micros-copy observations appear as isolated pieces ofinformation in his curious search for truthabout Nature, rather than as systematicallyorganized and extensive studies on a few sub-jects (6, 8).The extraordinary variety of things investi-

gated by Leeuwenhoek cover an immense fieldand contain studies on matters botanical,chemical, microbiological, physical, physiologi-cal, medical, and zoological. These have beencompiled by Miall (9) and Richardson (10), andinclude observations in part of the following.

I According to Dobell (6), Leeuwenhoek signed his namein different ways. Before 1683 he generally used the spellingAntoni Leeuwenhoeck, with the Christian name endingwith a long i (equivalent to English y) and the surnamewith ck, and without van; also sometimes Antonj Leeuwen-hoek until 1685 when he inserted van. Various Englishversions of his letters show 19 different ways of spelling hissurname.

260

Animalcules: Molds on meat; protozoa, bac-teria, and yeast in water and various sorts ofinfusions; microorganisms in scrapings fromteeth.Blood: Red blood cells from many animals

and man; capillary flow of blood through tail oftadpole, caudal fin of eel, web of frog's foot,membrane of bat's wing.Feathers: Structure of feathers from various

birds.Gunpowder: Microscopic nature before and

after firing.Hair: Color and structure of hair or fur from

bear, beaver, elk, man, sheep.Insects: Structure of the eye, optic nerve,

brain, mouth parts, legs, thorax, and abdomenof the bee, beetle, gnat, fly, louse, mite, silk-worm; spider and its web. First noticed thedifference in posture of anopheline and culicinemosquitoes in water.Minerals: Structure of metals (gold, silver,

copper), rocks, crystals, salt; properties of amagnet.Muscle fibers: Sections of muscles from var-

ious fish, duck heart, whale.Scales: Structure of scales from many fish.Spermatozoa: Structure of spermatozoa from

many species; he thought sperm was the verita-ble germ, which was only hatched by the fe-male.

Spices, nuts, seeds: What made pepper hot;the structure in relation to smell and taste ofcoffee, tea, nutmeg, ginger, sage, etc.

Trees and plants: Examined leaves and sec-tions of bark and wood from cork, elm, fir,ebony, lime, oak; plant and vegetable struc-tures, establishing differences between mono-and dicotyledenous plants; why nettles sting,etc.The scope of this paper is limited to the dis-

covery of bacteria, and the above topics studiedby Leeuwenhoek will not be discussed in detail.The information is available in the literaturecited (1-13, 18).

LEEUWENHOEK TERCENTENARY 261

ANT ONWtS A LEOuwENRo~t.

FIG. 1. From Arcina Naturae Detecta ab Antonio van Leeuwenhoek (1695). Delphis Batavorum, apudHenricum a Krooneveld (17). (Courtesy John Martin Collection, Health Sciences Library, University ofIowa.)

LEEUWENHOEK'S MICROSCOPES (14). This first communication describes the mi-croscopy observation of molds, and the sting of

The scientific world first learned of Leeuwen- a bee. For the next 40 years, Leeuwenhoekhoek's microscope in 1673 when R. de Graaf studied with endless patience and extraordi-sent a communication (Fig. 2) to Henry Olden- nary acuteness the many items listed above.burg, Secretary of the Royal Society of London Little information is available about how

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I speeiwew i few.O*feriabist wude, da Mkeroefcepe, eutriedby AM Leewenhoeck ia Holland, lately cO awuicated by Dr.Regnerus de Graas

rHE perfon communicating thefe Obfervations, by and1 by to be delivered, mentions in a Letter ofhis, written

from Delph April.28. 1673. that one Mr. Leewetesheec hathlately contrived Microrcopes excelling thofe that have beenhitherto made by wfIttchio Ditii and others ; adding,that hehath given afpeciawn of their excellency by divers ObCervati-oan and is ready to receive difficult talks for more, if theCu-dous here {hall pleare to lfnd him (ruch: Which they are notlike to be wanting in.

7he Ob/ervatiew: sthuifelves.X. The dewld-upon skin, fldb, or other hings, hath been

by fome reprefented to be Mott out in the form ofthe flalks ofVegetablesliss that kome of thofe (lalks appeared with round

s at the end, lbuce with bloiflm-like leavs But I doobFve limb Mould to (boot up firfi with a (Iraight tranfparent(alk, in which(alk isdrivenupa globous fubfance, whichfor the mofi part places it felfat the top ofthe [talk, and is fol.lowd by another globuldriving out the fift either fide.ways,or at the top, and that is fucceeded by a third and more fiachglobuls;all which makeup at laftone great knob on the (talk,an hundred times thicker than the fialk itif. And this knobindeed confifts of nothing elfe than of many fmall roundithknobs, which being multiplied, the big knob begins to burftafIunder, and then reprefents a kind of Blofl~oms withLeaves.

2. The slin ofa Bee I fiod to be of another make than -itbath beco deicribed by others. For I have obferved in ittwo other flings, that are lodged within the thicknefis of thefirfi fling, each baving its peculiar lheath.

3. Furth rFIG. 2. First scientific announcement ofLeeuwenhoek's microscope and observations in the Philosophical

Transactions of the Royal Society ofLondon (14).

Leeuwenhoek ground his small lenses, or howhe assembled his microscopes, for he never re-vealed his techniques. The microscopes con-sisted of a highly polished double-convex lensmounted in pierced and beveled openings be-tween two small (about 2 by 4 cm) brass, silver,or even gold plates, which were riveted to-gether (Fig. 3). Leeuwenhoek's special skill layin polishing and mounting the lens between themetal plates, in obtaining the proper source oflight, and in focusing on the object. Objects tobe viewed were mounted on a small pin or

specimen holder and brought into focus by ad-justing two or three threaded screws, whichmoved the specimen in various ways in front ofthe lens.Leeuwenhoek either built microscopes mag-

nifying several hundred times and with a re-solving power of about 1 Aum, or he used aspecial technique for viewing and lighting ob-jects that he never divulged. According to Roos-eboom (11), the most powerful of his instru-ments still in existence (Utrecht UniversityMuseum) magnifies 275x and has a resolving

262 PORTER BACTERIOL. REV.


S i ser

'I

..

I

S

I

I

IFIG. 3. Three microscopes made and used by Leeuwenhoek between 1673 and 1723. Left, Front or viewing

side showing small lens in the metal plate (1.8 by 4.0 cm); center, longitudinal view; right, back view ofinstrument. From Rooseboom (11) (courtesy ofA. J. F. Gogelein, Director, National Museum for the Historyof Science, Leiden, Netherlands).

power of 1.4 gm, despite scratches on the lens.On the other hand, Cittert (13) states that oneof Leeuwenhoek's lenses has resolving power of0.7 atm, and unstained cells of 5 pum, andstained ones of 1 to 2 tIm, are easily observablewith it.Many persons have wondered why Leeuwen-

hoek preferred a simple microscope for his sci-entific observations rather than a compoundone, which was already known. The compoundinstrument requires a less powerful lens sys-tem, provides a larger field of view, and iseasier to use because the object can be placed ata greater distance from the lens. Rooseboom(11) explains that this

is readily understandable if we compare thechromatic aberration of the two types of micro-scope. With the compound one, the image

formed by the objective, which shows coloredfringes, is once more enlarged, together with allits defects, by the eyepiece. With a single, short-focus lens-although, admittedly, the imagesformed by the different component rays ofwhitelight do not fall in one and the same plane, andthey too differ in size-the simple microscope isheld so close to the eye that one sees the imagepractically from the center of the lens ... andthe contours hardly show any colored fringes atall.

Once Leeuwenhoek became well known formaking microscopes he was visited by manynotable people, including Queen Mary of Eng-land, Frederick I of Prussia, and Peter theGreat of Russia. He frequently demonstrated tovisitors the transition of blood from the arterialto the venous sytem, and thereby confirmed

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264 PORTER

William Harvey's theory of the circulation ofthe blood. For such demonstrations he designeda special apparatus, the "aalkijker" or aquaticmicroscope (Fig. 4). By looking through themicroscope mounted in front of a glass tubecontaining a small eel in water, the observercould see the erythrocytes flowing through thecapillaries of the tail fin.Although Leeuwenhoek gave several of his

microscopes to people as gifts, he never soldone. Upon his death he bequeathed 26 micro-scopes to the Royal Society of London, saying:"Every one of them ground by myself andmounted in silver . .. that I extracted from the

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ore ... and therewithal is writ down whatobject standeth before each little glass" (2, 6).The Society carefully catalogued and describedthe microscopes and their mounted objects.After about a century they were supposedlyborrowed for inspection and never returned.The remainder of Leeuwenhoek's microscopesand lenses were put up for sale in Holland on 29May 1747. There were 419 lenses, three ofwhich were rock crystal. Of these lenses, 247were in complete microscopes, many with anobject to be viewed still in place. Two of themicroscopes were said to have two lenses andone had three. The other 172 lenses were

0 :0 I0.:

FIG. 4. Drawing ofLeeuwenhoek's aquatic microscope. Left, Resilient metal apparatus (fig. 9) for mount-ing microscope (fig. 8) at top left-hand side. Right, Glass tube containing a small eel (fig. 13). Center, Aquaticmicroscope (fig. 10) ready for use with glass tube held in place by resilient metal behind the microscope.Special fittings (fig. 11 and 12) for admitting and focusing incident light to the top of microscope. FromRooseboomn (11) (courtesy ofA. J. F. Gogelein, Director, National Museum for the History ofScience, Leiden,Netherlands).

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mounted between plates; of these, 160 plateswere of silver, 3 were of gold, and 9 were ofbrass (20). Supposedly, some of those made ofgold and silver were sold according to weight.Probably no other microscopes have ever beensold on such a basis (7).

Specifications for making a replica of Leeu-wenhoek's microscope have been clearly de-scribed by Walter and Via (19).

DISCOVERY OF BACTERIA AND OTHERMICROORGANISMS

From the many letters of Leeuwenhoek thatfollowed his first one in 1673 concerning molds(Fig. 2), it is a bit difficult to say exactly whenhe first saw bacteria and other microorganisms.But in 1674 he began to write about his studieson protozoa, and the following year he observedseveral kinds in canal water and in infusions ofpepper and other spices. By this time he hadperfected his microscopes and techniques, buthe never revealed the methods used for makinghis best observations, since he kept these forhimself.On 9 October 1676 Leeuwenhoek sent a sev-

enteen and a half page letter to Oldenburg inLondon outlining his ingenious observations on"animalcules" in various kinds of water andinfusions; the observations covered a period ofabout a year previous to his writing the letter.This unique document is on file in the archivesof the Royal Society (15), and it has been care-fully translated by Dobell (6), Cohen (4), andothers. The best translation and reproduction isthat of Cohen in his excellent monograph: TheLeeuwenhoek Letter. Cohen states, however,that the handwriting is that ofa copyist and notLeeuwenhoek's, although he did make somecorrections in the manuscript and he signed it.Since the letter is not the handwriting of Leeu-wenhoek, none of the pages will be reproducedhere, although translated quotations will begiven to show his discoveries. His handwritingis shown in Fig. 6.

Certain sections of the 9 October letter thatundoubtedly refer to Leeuwenhoek's discoveryof bacteria and other microorganisms in waterand infusions ofpepper are as follows (4, 6, 12):

[The 1st Observation on Pepper-Water]: On 24April 1676 ... the fourth sort of animalculeswhich floated about amongst the other threesorts, were incredibly small, indeed so small... that I judged if all of 100 of these ... werestretched out against one another, they would'not reach the length of a small sand-grain. Thisbeing true, then ten hundred thousand of theseliving creatures would not be able to fill thevolume of a small sand-grain.

[The 3rd Observation on Pepper-Water]: The


4th of June.... I saw a great multitude ofliving creatures in one drop of water, amount-ing to no less than 8 or 10 thousand, and theyappear to my eye through the microscope ascommon sand does to the naked eye.

[The 5th Observation on Pepper-Water]: The6th of August.... This was to me, among allthe marvels that I have discovered in Nature,the most marvellous of all; and I must say formy part, that no greater pleasure has yet cometo my eye than these spectacles of so manythousands of living creatures in a small drop ofwater moving among one another, each individ-ual creature with its particular movement. Andif I said there were a hundred thousand in onedroplet. . . I should not err. Others viewing thiswould multiply the number by fully ten times,but I state the least. My method for seeing thevery smallest animalcules I do not impart toothers; nor how to see very many animalcules atone time. This I keep for myself alone.

All authorities agree that the above observa-tions by Leeuwenhoek constitute the originaldiscovery of bacteria.

In Leeuwenhoek's letter no. 32 of 14 June1680 to Thomas Gale, at that time Secretary ofthe Royal Society, he recorded (3, 17) the firstmicroscopy study of yeast in fermenting beerwort and noted that they gave off much gas. Hesaid, "some of these seem to be quite round,others are irregular, and some exceeded theothers in size consisting of two, three, or four ofthe aforesaid globules joined together." In thesame interesting letter he states that he hasheard that no living creature can generate it-self when placed in tightly stoppered vessels.Thus he decided to study the topic by preparinga clean-water infusion of pepper in two glasstubes, one remaining open to the air and theother sealed (G, in Fig. 5). After the third dayhe examined the water from the open tube andsaw many animalcules under the microscope,but he decided to wait until the fifth day tobreak the seal and examine the contents of theclosed tube. When he did this he was amazed tofind many bacteria. This was the first demon-stration that organisms live and multiply un-der facultative or anaerobic conditions, butLeeuwenhoek was unable to appreciate the fullsignificance of his study.

If any one should doubt that Leeuwenhoekfirst saw and described bacteria and certainother microorganisms in 1676 and again in1680, proof of this certainly came in 1683. Aletter (16) addressed to the Royal Society on 17September 1683 is probably as famous in theannals of microbiology as the one of 1676 or anyletter ever written. The letter contained an ac-count of the types of animalcules seen in thesaliva (spittle) and tooth scrapings from his

266 PORTER

A LFIG. 5. Leeuwenhoek's sealed tube for determin-

ing ifanimalcules would grow in the absence ofopenair. Pepper (ABKL)-rain water (BCIK) infusion withtube sealed at G (2, 6, 17).

mouth and those from others, as well as specu-

lation on how the organisms got into themouth.Figure 6 is a page from Leeuwenhoek's 1683

letter, which demonstrates his handwritingand clearly describes his drawings of microor-ganisms (Fig. 7). The translation (6, 16) of partof the previous and following pages, as well asthe one shown in the figure, follows:

The biggest sort had the shape of A [Fig. 7];these had a very strong and nimble motion, andthey shot through the water or spittle, as a Pikedoes through the water. These were almost al-ways few in number.The second sort had the shape of B. These

often spun about like a top, and sometimes tooka course as shown between C and D. They weremore numerous than the first.

In the third sort I could not well distinguish

the fig: sometimes, it seemed to be oval and atother times it was round. These were so smallthat I could see them no bigger than fig. E; yetthey went ahead so nimbly, and they hovered sotogether, that I can compare them to nothingbetter than a big swarm of gnats or flies, flyingin and out among one another. These lastseemed to me to be ... several thousand in anamount of water, or spittle (mixed with theaforesaid material) no bigger than a sandgrain....

Besides these . .. there were a great quantityof streaks or threads of different length but ofthe same thickness, some bent, others straight,as fig: F, and which lay disorderly ravelled to-gether. Because I had seen formerly in waterlive animals that had the same fig., I madeevery effort to see if there was any life in them;but I could make out not the least motion, thatlooked like anything alive in any of 'em....The biggest sort (whereof there were a great

many) bent themselves in curves as they movedlike fig. G.

LEEUWENHOEK THE MANThe biography of Leeuwenhoek can be re-

lated quickly, because there is so little informa-tion about his personal activities during agreater part of his life. He was born in Delft,Netherlands, 24 October 1632, and he diedthere in his 90th year (26 August 1723) and wasburied in the Old North Church. He was fromgood Dutch stock, although not of great distinc-tion; his genealogy is outlined in detail bySchierbeek (12). As a boy he had some school-ing and lived for awhile with an uncle who wasan attorney and town clerk at Benthuizen- ashort distance from Delft. There is no indica-tion, however, that he planned to be a lawyer.When Leeuwenhoek was 16 he went to Am-

sterdam to apprentice as a linen draper. Afterqualifying, he also became the bookkeeper andcashier in the shop where he worked. In aboutsix years (1652-54) he returned to Delft, mar-ried (18) and sired five children (all but onedaughter, Maria, died in childhood). He boughta house and shop, and set up in business as adraper. At the age of 27 or 28 he was appointedChamberlain of the Council Chamber of theSheriffs of Delft. This position paid only a smallsalary, but it did not require arduous or time-consuming duties so he could devote more at-tention to his study of Nature. He did, however,do some work as a surveyor and as minicipalwine-gauger. When and why Leeuwenhoek be-gan to grind and mount lenses is not known.Leeuwenhoek was one of the most original

and curious men who ever lived. It is difficult tocompare him with anybody because "he be-longed to a genus of which he was the type and

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VOL. 40, 1976 LEEUWENHOEK TERCENTENARY 267

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FIG. 6. Page from the original manuscript ofLeeuwenhoek's letter 39 to the Royal Society ofLondon dated'17 September 1683 in which he described the bacteria in Fig. 3. This is a good example ofhis handwriting atthe age of51. See text for translation. (Courtesy ofDobell [6].)

only species" (5), and when he died his line nent professors, knew Latin or Greek togetherbecame extinct. with their native language, and acquired andEven in the 17th century most great natural- rearranged traditional knowledge to suit their

ists were learned men, who studied under emi- own needs. Leeuwenhoek had some formal edu-

a

Allift

268 PORTER

:$A _- .. I-0D

C C "

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FIG. 7. Leeuwenhoek's drawings of bacteria (ba-cilli, cocci, spirillum) from the human mouth as

described in letter no. 39, 17 September 1683. SeeFig. 5 and text for descriptions (7, 13).

cation, but he studied under no distinguishedprofessor, owed nothing to any university, andknew no language but his own. He was largelyself-educated and had to rely entirely on hisown innate genius and curiosity in studying thesecrets of Nature. He could only ask Naturequestions in 17th century Dutch, and then puz-

zle about her answers by himself. Because ofhis originality, discoveries, and extensive con-

tributions, Leeuwenhoek was elected a foreignmember of the Royal Society of London in 1680.No one can consider Leeuwenhoek as one of

the great philosphers of his day. He did, how-ever, have a definite opinion on two great bio-logical questions of the time: spontaneous gen-eration and the origin of species. His own obser-vations supported the reasoning of Redi, thatwhen things arose independently in infusionsor tissues they were actually introduced fromwithout. He believed in fixed species, and heexpressed views similar to those for which Lin-naeus became famous in the next generation.Although Leeuwenhoek studied most thingssuperficially by standards of today, he mademany great and original discoveries, and heliterally founded protozoology and bacteriologyfrom nothing."A few people are born great, some have

greatness thrust upon them during their lives,and other achieve greatness by themselves andare fully recognized later" (1). Leeuwenhoekqualifies best under this last category, but healso belongs to another important class. He wasone of the unique persons in history who truly

penetrated and discovered some of the greatsecrets of Nature.Not only microbiologists, but everyone who

has lived since Leeuwenhoek, owe much to thisgifted man. On the occasion of the tercentenaryofhis discovery of bacteria we should gratefullyacknowledge and pay tribute to him, as wasdone graciously on his 300th birthday (7).

LITERATURE CITED1. Becking, L. B. 1924. Antoni van Leeuwenhoek,

immortal dilettant (1632-1723). Sci. Monthly18:547-554.

2. Bulloch, W. 1938. The history of bacteriology.Oxford University Press, London.

3. Chapman, A. C. 1931. The yeast cell: what didLeeuwenhoek see? J. Inst. Brewing 37:433-436.

4. Cohen, B. 1937. The Leeuwenhoek letter. Soci-ety of American Bacteriologists, Baltimore.

5. Dobell, C. 1923. A protozoological bicentenary:Antony van Leeuwenhoek (1632-1723) andLouis Joblot (1645-1723). Parasitology 15:308-319.

6. Dobell, C. 1932. Antony van Leeuwenhoek andhis "little animals." Harcourt, Brace and Co.,New York.

7. Fred, E. B. 1933. Antony van Leeuwenhoek, onthe three-hundredth anniversary of his birth.J. Bacteriol. 25:1-18.

8. Haaxman, P. J. 1871. Antony van Leeuwen-hoek. Nederlandsch. Tijdschr. Geneeskunde15(II):1-86.

9. Miall, L. C. 1912. The early naturalists, theirlives and works (1530-1789). Macmillan andCo., London.

10. Richardson, B. W. 1900. Disciples of Aescula-pius, vol. I. Hutchinson & Co., London.

11. Rooseboom, M. 1956. Microscopium. NationalMuseum for the History of Science. Leyden,Netherlands.

12. Schierbeek, A. 1930. Een paar ilieuwe bijzonder-heden over van Leeuwenhoek. Nederland.Tijdschr. Geneeskunde 74:3891-3899.

13. van Cittert, P. H. 1933. The "van Leeuwenhoekmicroscope" in possession of the University ofUtrecht. Akad. Wetensch. Amsterdam, Proc.Sec. Sci. 36:194-196.

14. van Leeuwenhoek, A. 1673. A specimen of someobservations made by a microscope, contrivedby M. Leewenhoeck in Holland, lately com-municated by Dr. Regnerus de Graaf. Philos.Trans. R. Soc. London 8:6037-6038.

15. van Leeuwenhoek, A. 1677. Observations com-municated to the publisher by Mr. Antonyvan Leeuwenhoeck, in Dutch letter of the 9thof October 1676: concerning little animals byhim observed in rain-well-sea- and snow-wa-ter; as also in water wherein pepper had laininfused. Philos. Trans. R. Soc. London 12:821-831.

16. van Leeuwenhoek, A. 1684. An abstract of aletter from Mr. Anthony Leevvenhoeck atDelft, dated Sep. 17, 1683, containing some

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microscopical observations, about animals int the scurf of the teeth.... Philos. Trans. R.Soc. London 14:568-574.

17. van Leeuwenhoek, A. 1695. Arcana naturae de-tecta ab Antonio van Leeuwenhoek. T. II,Delphis Batavorum, apud Henricum a Kroo-neveld.

18. van Seters, W. H. 1968. van Leeuwenhoeks


tweede huwelijk. Nederland. Tijdschr. Ge-neeskunde 112:1258-1261.

19. Walter, W. G., and H. Via. 1968. Making aLeeuwenhoek "microscope" replica. Am. Biol.Teacher 30:537-539.

20. Weller, C. V. 1932. Antony van Leeuwenhoek,1632-1723. Ann. Internal Med. 6:573-584.

antony van leeuwenhoekl: tercentenary of his discovery of

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