Send-Brieven / Epistles
Cabinet of Wonders

This "cabinet of wonders" has all of the 140 figures, originally copperplate etchings, that accompanied half of the 46 letters of the Send-Brieven / Epistles.

This page has Letters XXIV, XXV, XXVI, XXVIII, XXX.

Clicking on the underlined Roman numerals on the table below will take you to that letter's summary and figures.

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Letter XXIV

to: Cornelis Spiering
May 22, 1716

Dutch title: Aanmerkingen op de schobben van eenen Karper.

English title: Comments on the scales of a carp.

Letter XXIV of May 22, 1716 to Den Heer Cornelis Spiering, Heere van Spierings-Hoek, Raat ende Out-Schepen deser Stad - Lord of Spierings-Hoek, Council and former Alderman of the City Van Leeuwenhoek's summary of the contents: Comments on the scales of a carp. Every year, new scales grow on the fish. This is thoroughly refuted. The scales brought before the magnifying glass in various ways. If one can not separate the scales by cutting; then one knows the age of the fish very closely from the contours, that lie on the scales. There is a time in the year, when the growth of the body stops. This appears also from carvings, that are drawn in cow horns. We see it also in the moult from animals; and in the exchange of feathers in birds. Considering why it is that in a pond, where in many years there have been large carp, no young carp come forth. A great number of spawn grains found in a linge fish. The same, in proportion, applies to carp. From each spawn grain from a cod come thousands of living little animals from cod roe. From the abundant spawn-grains, and male seeds, of the fish come few young, seeming to show that fish are using the same spawn-grains as food. Eels devour more spawn than fish. The great fishes are harmful in a pond. A great number of spawn grains in the gurnet. The large devouring fishes have no spawn; but carry the young living in her body. Considering whether the many large whales, that were first caught, were not more than 1,000 years old. The fish don't die of old age, and why?	Letter XXIV of May 22, 1716 to Den Heer Cornelis Spiering, Heere van Spierings-Hoek, Raat ende Out-Schepen deser Stad - Lord of Spierings-Hoek, Council and former Alderman of the City Van Leeuwenhoek's summary of the contents: Aanmerkingen op de schobben van eenen Karper. Alle jaaren groeit 'er een nieuwe schobbe aan de visch. Dit word zeer tegengesproken. De schobben op verscheyde manieren voor het Vergroot-glas gebragt. Als men de schobbens, door het snyden, niet van een kan scheyden; dan men den ouderdom der vissen zeer naar weeten uyt de ommetrekken, die op de schobbens leggen. Daar is een tyd in 't jaar, als de grootmaaking der lichaamen stil staat. Dit blykt uyt de krappen, die in de hoornen der koien getekent staan. Wy zien het ook in het verhairen van de dieren; en in het verwisselen der veeren in de vogelen. Bedenking waarom dat in een Vyver, waar in veele jaaren groote Karpers zyn geweest, geene jonge Karpers voorten koomen. Groot getal van Kuyt-greynen in eene Lenge gevonden. Het zelve, naar proportie, op de Karpers toegepast. Tegen yder kuytgreyntje van eenen Kabeljauw komen wel duyzent levende diertjens voort uyt een Kabeljauws hom. Uyt de overvloedige kuytgreynen, en mannelyke zeeden, van de visschen, waar uyt weynige jongen voortkomen, schynt te blyken dat 'er visschen zyn die dezelve kuytgreynen tot voedzel gebruyken. De Aalen verslinden veel kuyt van visschen. De groote visschen, Winden, zyn schadelyk in een Vyver. Groot getal van Kuyt-greynen in de Garnaat. De groote verslindende visschen hebben geen kuyt; maar draagen de jongen levend in haar lichaam. Bedenking of de zeer groote Walvisschen, die eerst gevangen wierden, niet wel 1000 jaaren out waren. De visschen sterven van geen ouderdom, en waarom?
English     ||    Nederland Van Leeuwenhoek's summary of Letter XXIV
Figure 1: scale of 30-year old carp cut slantwise showing a year's growth Letter XXIV to: Den Heer Cornelis Spiering, Heere van Spierings-Hoek, Raat ende Out-Schepen deser Stad - Lord of Spierings-Hoek, Council and former Alderman of the City May 22, 1716 Dutch title: Aanmerkingen op de schobben van eenen Karper. English title: Comments on the scales of a carp. Letter XXIV Figure 1
Figures 2 and 4: another scale from the same carp cut even more slantwise; the piece of scale in actual size Letter XXIV to: Den Heer Cornelis Spiering, Heere van Spierings-Hoek, Raat ende Out-Schepen deser Stad - Lord of Spierings-Hoek, Council and former Alderman of the City May 22, 1716 Dutch title: Aanmerkingen op de schobben van eenen Karper. English title: Comments on the scales of a carp. Letter XXIV Figures 2 and 4
Figure 3: section of a scale scraped from a carp Letter XXIV to: Den Heer Cornelis Spiering, Heere van Spierings-Hoek, Raat ende Out-Schepen deser Stad - Lord of Spierings-Hoek, Council and former Alderman of the City May 22, 1716 Dutch title: Aanmerkingen op de schobben van eenen Karper. English title: Comments on the scales of a carp. Letter XXIV Figure 3

Letter XXV

to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn.
June 12, 1716

Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen

English title: How many straw stalks and barley shoots come out of a grain of barley

Letter XXV of June 12, 1716 to Professors Cink, Narrez, Rega, and other Gentlemen of the College of the Wild Boar. Van Leeuwenhoek's summary of the contents: How many straw stalks and barley shoots come out of a grain of barley: fruitless effort trying to find out. The plant, that lies closed up in the barley, cut in cross-section: parts of the plant, or the beginnings of the parts, discovered there. The beginnings of the straw stalks cut lengthwise. Membranes in the inner parts, to protect them. Pori in the plant indicated: also valves, both for the sap that is transported upwards, and for that which is closed off downward. Meal in the plants. Grass in the plants: in each grain of wheat and barley not only were plants discovered, but also the beginnings of of the fruit. Another part of the plant, in a barley grain, indicated with its surrounding leaves. The fruit of the barley shoot once again discovered in the barley grain. The same discovery yet again. Different observations made concerning the young barley plants. Sand, in which sprouting barley had lain, remained hanging on the sprouting roots: reasons for that. Why the mealy material is closed up in the barley, wheat, etc; precisely, in order to nourish the young plants. Is explained why the barley, lying in damp earth sprouts and develops. Explanation of this development. Tubes in the plants: valves in the tubes. How the valves lie stretched out. The saps going up, stay up there: those going down, stay down. No plants can come forth from rotting, so few as living creatures. The seeds of apples from China dissected. In some of the seeds three special plants were closed up.	Letter XXV of August 21, 1714 to De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. Van Leeuwenhoek's summary of the contents: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen: vruchtelooze moeite daar omtrent gedaan. De plant, die in een Gerst opgesloten leyt, doorsneden: deelen van de plant, of beginzels van die delen, daar in ontdekt. De beginsels der stroo-halmen in haare lengte doorsneden. Membranen in de inwendige deelen, om dezelve te beschermen. Pori in de Plant aangewezen: ook Klapvliezen, zoo wel voor de sappen die opwaart gevoert worden, als die nederwaart gestooten worden. Meel in de planten. Gras in de planten: in yder tarwe en gerstje niet alleen eenige planten, maar ook het beginsel van de vrucht ontdekt. Een ander deel van de plant, in een gerstje, met zyne omleggende bladeren aangewezen. De vrucht ofte Garst-air wederom in de Gerst ontdekt. Dezelfde ontdekking nochmaals gedaan. Verscheide waarnemingen omtrent jonge Gerst-plantjes gedaan. Sand, waar in Gerst te spruyten gelegen had, bleef aan de uytgeschotene worteljes hangen: reden daar van. Waar toe de meel-achtige stoffe in de Gerst, Tarwe, enz. opgeslooten is; te weeten om de jonge plantjens te voeden. Word uytgelegt waarom de gerst, in vochtige aarde leggende, schiet en wasdom krygt. Uytlegging van deze wasdom. Pypjes in de planten: Klap-vliesjes in de pypjes. Hoe die Klap-vliesjes gestrekt leggen. De sappen naar boven gestooten, blyven boven: die naar beneden gestooten worden blyven beneden. Uyt verrottinge konnen geene planten, zoo weinig als levende schepsels, voortkomen. De zaaden van appelen van China ontleet. In eenige van die zaaden waren drie byzondere planten opgesloten.
English     ||    Nederland Van Leeuwenhoek's summary of Letter XXV
Figure 1: barley grain with rind removed Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 1
Figure 2: cross sections of three beginnings of barley straw blades from within a grain Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 2
Figure 3: barley grain showing little leaf blades waiting to sprout Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 3
Figure 4: straw blade taken from HI in Figure 3 showing the beginning of the stalk's growth Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 4
Figure 5: fruit discovered between the blades within a barley grain Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 5
Figure 6: barley shoot Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 6
Figure 7: barley shoot (rotated right) Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 7
Figure 8: blade of barley grass Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 8
Figure 9: piece of barley root taken from sand and washed, showing little sand grain still entangled in the little hairs of the root Letter XXV to: De Heeren Professoren Cink, Narrez, Rega, en verdere Heeren van het Collegie van 't wilt Swyn. June 12, 1716 Dutch title: Hoe veele stroo halmen en Gerst-airen dat uyt een greyntje van Gerst voortkomen English title: How many straw stalks and barley shoots come out of a grain of barley Letter XXV Figure 9

Letter XXVI

to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Emperial and Royal Majesty's historian
June 22, 1716

Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes.

English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules.

Letter XXVI of June 22, 1716 to Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Emperial and Royal Majesty's historian Van Leeuwenhoek's summary of the contents: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules; which lie enclosed in very thin little sheaths. Difference in size of the same globules. The mealy material of wheat, barley, etc., does not consist of round balls, as the writer had believed before this. Many such parts have an inward arch. The arch is not always seen through the magnifying glass, and why? How the mealy parts grow and expand; every little part of the said mealy material obtains its nourishment through the little vessels of the sheath. Amazement at the translucency of the meal globules. The smallness of the same globules indicated in a rough sketch. Whether the meal globules are also covered with a little sheath the author will, he believes, not be able to discover. Whether in the larger globules yet smaler globules lie enclosed? Observations made concerning the meal globules; and the same mixed with a drop or two of water, and thus placed on a clean glass; which was then flattened. The meal globules also provided with a skin. When the meal globules are made warm and wet, the little rinds split off from each other. To what end is the arch or seam in the wheat grain made? The rind or bark of the wheat grains go from both sides to the middle of the same wheat grains, and have there two arches, so that they can be swollen up with water. The rinds are thus shaped, in that the wheat grains could be stripped in the stomachs of the hens, partridges, turkeys, etc. without shattering the same bark. In order to examine this more neatly the author has filled a glass tube with wheat and barley grains, and further with water; and everything was helped to boil, without the bark breaking. The above-mentioned bow, or seam, is also in the rye, barley, and oat. As the wheat grains and barley grains swell up more and more, the parts of the rind separate from each other, without breaking the rind. The meal globules placed before a glass, magnifying even more: and thus indicates that they have as much of a seam as the wheat grains. The meal globules again placed with a drop of water on a clean glass, and brought before it again: which take on the figure of a hook. The little mealy globules even change to a range of sizes. It is incomprehensible how many parts the size of a sand grain there are in the meal material. The bundles of meal material and the meal material itself, partly have a six-sided figure; without that there are few empty places between them: but not if they have lain in the water, etc. The parts of white bread described. The beans brought before the magnifying glass: the meal material of the beans mixed with water, and warmed, have another shape. Another observation concerning the mealy parts from the beans. The meal parts of beans lie in little bundles near each other: remarks on the little bundles. The little bundles cut through transversely; and the little meal parts enclosed there. The meal material of a green pea brought before the magnifying glass, mixed with water, warmed, etc. The mealy parts appear to be partially loosened. The beans do not agree well with some people. Some beasts do not want to eat them. The meal from beans moistened and warmed; etc. Various shapes confirmed, of the little beans, so treated. The meal of rice examined. The mealy bundles of the buckwheat lie enclosed in no sheath; and why? The meal from all corn must be taken in the above-mentioned manner, to be stripped out as food. The stool of pigeons examined; and meal particles, that were not stripped, found there. In the hens' dung nothing else discovered such as large pieces from the bark of barley. Little hairs in the slime of mold. Where it comes from. Particles from the rinds of wheat, barley, found in same stool. Mealy stuff in the coffee bean. Turkish wheat is composed of meal globules. The meal material of Turkish wheat is not so easily stripped out as is that of our wheat.	Letter XXVI of June 22, 1716 to Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian Van Leeuwenhoek's summary of the contents: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes: dewelke in zeer dunne vliesjes besloten leggen. Onderscheid van dezelve bolletjens in groote. De meel-stoffe van de Tarwe, Gerst, enz. bestaat uyt geene klootsche ronte, gelyk de Schryver voor dezen gelooft heeft. Veele zulke deelen hebben een inwendige boght. Die bogt word niet altyd door het Vergroot-glas gezien, en waarom? Hoe die meel-deelen groeyen en aanwassen; Yder deeltje van de gezeide meel-stoffe bekoomt zyn voedsel door de adertjes van het vlies. Verwondering over de doorschynendheit van die meel-bolletjens. De kleynheit van dezelve bolletjes in een ruwe schets aangewezen. Of die meel-bolletjes ook met een vliesje bekleedt zyn zal de Auteur, gelooft hy, niet konnen ontdekken. Of in de grooter bolletjes noch kleynder bolletjes besloten leggen? Waarnemingen omtrent de meelbolletjes gedaan; en dezelve met een droppeltje of twee water gemengt, en aldus op een schoonglas geplaatst; dewelke dan platachtig wierden. De meel-bolletjes ook met een huyt voorzien. Als die meel-bolletjes in de warmte koomen, en nat worden, splyten de schorsjens der zelven van malkander. Tot wat eynde de bogt of de naad in de Tarwe-greynen geschapen is? De schors of bast der Tarwgreynen gaet van beide de zyden tot in 't midden der zelve Tarw-greynen, en heeft daar twee bogten, om te konnen uytzwellen door het water. Die schorsen zyn aldus geschapen, op dat de Tarw-greynen in de magen der Hoenderen, Patryzen, Kalkoenen, enz. zonder verbryselinge der zelve basten, zouden ontdaan worden. Om dit netter te onderzoeken heeft de Auteur een glaze Tube gevult met Tarw en Gerst-greynen, en vorder met water; en dat alles aan 't kooken geholpen, zonder dat de basten quamen te breeken. De voornoemde bogt, of naat, is ook in de Rogge, Gerst, en Haver. Als de Tarw-greynen en Gerst-greynen meer en meer opzwellen, scheyden de deelen der schorse van malkander, zonder dat de schors koomt te breeken. De Meel-bolletjes voor een glas, dat noch meer vergroot, geplaatst: en aldus aangewezen dat ze zoo wel als de Tarwe-greyntjes eenen naat hebben. De Meel-bolletjes wederom met een droppel water op een schoon glas geplaatst, en voor 't veer gebragt: dewelke dan de figuur van eenen hoek aanneemen. Zelfs geschiedt 'er dan eenige verandering in de kleyne Meel-bolletjes, die tusschen de groote verspreydt leggen. Het is onbegrypelyk hoe veele deelen dat 'er zyn in de Meel stoffe van een zants grootte. De bondeltjes der Meel-stoffe en de Meel-stoffe self, hebben ten deele een Seszydige figuur; zonder dat 'er eenige ledige plaats tusschen beyden is: doch zoo niet als ze in 't water leggen, enz. De deelen van het blanke brood beschreven. De Boonen voor het Vergroot-glas gebragt: de Meel stoffe der Boonen met water gemengt, en by warmte gebragt, krygen een andere gedaante. Andere waarneemingen omtrent de Meel-deelen van de Boonen. De Meel-deelen der Boonen leggen in bondelkens by malkander: opmerkingen op die bondeltjes. Die bondeltjes overdwars doorsneden; en de Meel deltjes daar uyt besloten. De Meel-stoffe van een groene Ert voor 't Vergroot-glas gebragt, met water gemengt, warm gemaakt, enz. Die Meel-deelen schynen ligtelyk ontdaan te worden. De Boontjes bekoomen sommigen menschen niet wel. Sommige Beesten willen die niet eeten. Het Meel der Boonen natgemaakt, en gewarmt; enz. Verscheyde gedaante, die de Boontjes, soodanig gehandelt, aanneemen. Het Meel van de Ryst onderzocht. De Meel-bondeltjes van de Boekweyt leggen in geen vlies opgesloten; en waarom? Het Meel van alle koorn moet op de bovengemelde wyze ontdaan daan worden, om tot voedzel te gedyen. De afgang der Duyven onderzocht; en Meel-deeltjens, doch die niet ontdaan waren, daar in gevonden. In de Hoender drek niet anders ontdekt als groote stukken van de basten der Gerst. Hairtjes in den drek der Mosschen. Waar die van daan koomen. Deeltjes van de schorsen der Tarwe, Gerst, in den zelven afgang gevonden. Meel-achtige stoffe in de Koffy-boonen. De Turksche Tarw bestaat ook uyt Meel bolletjens. De Meel-stoffe van de Turksche Tarwe word soo ligt niet ontdaan als die van onze Tarwe.
English     ||    Nederland Van Leeuwenhoek's summary of Letter XXVI
Figure 1: meal globule, right; grain of sand, left Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 1
Figure 2: vaious sizes of wheat meal globules Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 2
Figure 3: wheat grain with seam Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 3
Figure 4: a section of the rind of a wheat grain showing arches to accommodate expansion Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Emperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 4
Figure 5: larger view of various sizes of rye meal globules showing seams Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 5
Figure 6: barley meal globules with elevated mounds after being heated in water Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 6
Figure 7: small piece of oat bread showing irregular meal parts with wrinkles and elevations Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 7
Figure 8: bean meal pieces; heated in water, right Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 8
Figure 9: bundle of bean meal pieces, some more roundish, lower right Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 9
Figure 10: cross-section of bean meal pieces showing bundle of empty sheaths after the meal globules extracted Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 10
Figure 11: section of bean meal pieces showing bundle with some empty sheaths and some still containing meal globules Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 11
Figure 12: water saturated meal of green pea, left; meal of green pea heated in water, center; slightly moistened meal of green pea Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 12
Figure 13: white bean meal slightly moistened, far left; warmed in water, near left; heated in water, near right; after more heating, far right Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 13
Figure 14: bundles of meal material enclosed in sheaths Letter XXVI to: Den Heere J. G. Kerkherdere, zyner Kerserlyke en Koninglyke Majesteyes Historicus - his Imperial and Royal Majesty's historian June 22, 1716 Dutch title: De stoffe, in de Tarwe, Gerst, enz. opgesloten, en die wy meel-noemen, bestaat uyt ronde doorschynende bolletjes. English title: The material closed up in wheat, barley, etc., that we call meal, consists of round translucent globules. Letter XXVI Figure 14

"Regions inaccessible, impenetrable, and imperceptible"

In his entry about the December 6, 1677 meeting of the Royal Society, Birch wrote of Robert Hooke (my emphasis):

But his design was rather to improve and increase the distinguishing faculties of the senses, not only in order to reduce these things, which are already sensible to our organs unassisted, to number, weight, and, measure, but also in order to the inlarging the limits of their power, so as to be able to do the same things in regions of matter hitherto inaccessible, impenetrable, and imperceptible by the senses unassisted.

"No Longer Any Doubt"

How the Royal Society validated
van Leeuwenhoek's observations.

It was one thing for van Leeuwenhoek to count how many and calculate how small. It was another thing for those without the lenses and the expertise, the members of the Royal Society, to believe him.

As Birch recounts in his History of the Royal Society, the members, in fact, did not believe van Leeuwenhoek. The process by which they came to accept the truth of his claims was an early test of the power of the developing discipline called "science".

The timeline on the table to the left includes events in London as well as letters van Leeuwenhoek wrote. It is not a complete list of the letters he wrote during these four years, only the ones relevant to the discussion below of the extraordinary claims that he made and the efforts that the Royal Society expended to replicate his results.

Further discussion of these letters is found on the pages for Period 1 and Period 2.

The timeline is divided into four sections in the discussion below:

Claims Published
April 1673 - September 1674

In a flush of quick success, the first half-dozen letters that van Leeuwenhoek sent to Henry Oldenburg were all published, at least in part, in Philosophical Transactions.

The first letter, April 28, 1673, replicated and expanded on several of Robert Hooke's observations in Micrographia. Mould, the stinger of a bee, and an eye of a bee. Oldenburg encouraged van Leeuwenhoek to do more.

Instead of looking closely at things he could already see, as did the other microscopists of the time, van Leeuwenhoek used his powerful little lenses to see things no one had ever seen before. Not only that, there seemed to be more of them in a drop of blood than there were people in Holland. On June 1, 1674, van Leeuwenhoek described, for the first time, red blood cells and emphasized their tiny size.

First, he disclosed his procedure, referencing a drawing (see right):

I shall herewith communicate the Manner how I have observ'd, among other things, Blood and Milk.

I did my self prepare divers sorts of very slender hollow Glass-pipes (See Fig. I.) as A B, of which some were not thicker than a mans-hair; and the slenderer they are, the clearer will they make the red Globuls of the Blood appear. But, for seeing the Crystalline water in which those Globuls move, and for observing also how they subside, these Pipes may be made somewhat thicker. ...

Note that he realized early on that the glass pipe itself can act as a lens. Just as smaller lenses were more powerful, so, for the same reason -- increased radius of curvature -- "slenderer" pipes made the blood appear more clearly.

This pipe with the blood in it, I lay upon a piece of white paper and with my nail break a little piece from it, as Fig 2d or 3d; and set it to the pin of my Microscope, having first a little wetted the pin with my spittle or a little turpentine, to make the pipe stick to it; or else I take the whole Glass-pipe, and with my hand hold it before the microscope.

Not only does he reveal his procedure and enclose a drawing of his pipe:

And that the Curious in your parts might themselves see this, I have used the freedom of sending you some of the said hollow Pipes, by the means of which I hope my above-mentioned speculations will be verified.

He also sends some of the pipes themselves, and then tells why:

The red Globules of the Blood I reckon to be 2500 times smaller than a grain of sand; which perhaps will to many seem incredible.

Later in the same letter, he has moved on to discuss his special pipes and his technique for getting a cow's brain tissue in front of his lens. Again, he was forthcoming about his tools and methods:

Now that the Curious may be assisted to view the particles of the brain, I herewith send also some Glass-pipes, by me contrived for that purpose.

He included drawings of these pipes, also (see right). In addition to the two different kind of pipes he sent, van Leeuwenhoek also sent samples of his specimens in little envelopes so that his observations could be verified. The cork and elder were among the samples recovered by Brian J. Ford in the late 20th century and discussed in The Leeuwenhoek Legacy, where he looked at them through some of the surviving lenses. Indeed, we know now, van Leeuwenhoek had a tool that let him see what he claimed to have seen.

Which kind of progress of growing I apprehend may in some manner be seen in the Pith of Wood, in Cork, in the Pith of Elder, and also in the White of a Quill; of which three last I have sent you and your curious Friends some small particles, cut off with a sharp Pen-knife, thinking it well worth their observation.

Van Leeuwenhoek then added a few words about technique.

Only I would here advertise, that when any of these particles is applied to the pin of such a kind of Microscope as mine is, the instrument may be held within doors and in the shade, yet held to the free Air, as if with a Telescope you would look upon the Stars in the Firmament.

The last of these early letters, written on September 7, 1674, and published the same year at the end of volume 11 of Philosophical Transactions, observed the structure of the human eye and crystals of salt and chalk. At the end of it, van Leeuwenhoek changed subjects abruptly to tell of what he found in water from a nearby lake, Berckelsemeer:

... among all which there crawled abundance of little animals, some of which were roundish; those that were somewhat bigger than others were of an Oval figure: On these latter I saw two legs near the head and two little fins on the other end of their body.

At the time, he said nothing else about their size and number. These letters do not show a secretive amateur, they show a forthright researcher who was astonished by what he saw and was eager to help others see, too.

Claims Unpublished
October 1674 - October 1676

Of van Leeuwenhoek's next twelve letters of observations, only three were published in Philosophical Transactions. He did not publish them in his Dutch/Latin collected works, either; they remained unpublished until 1930, when Dobell translated them for a journal article and then in 1939 in volume 1 of Alle de Brieven / Collected Letters.

The unpublished letters increasingly revealed the little world that van Leeuwenhoek was the first to see. The two published letters, however, dealt with subjects that were understandable in the everyday world. We don't have any direct evidence about the Royal Society's editorial process to explain why some of van Leeuwenhoek's letters went unpublished. We know that Oldenburg did not publish every letter he received from his many correspondents around the world. We also know that few correspondents had as many articles published in their whole careers as van Leeuwenhoek had during his first few years alone.

For whatever reason, the letter that van Leeuwenhoek wrote on October 19, 1674, was the first that did not get published. It describes worm eggs, the structure of metals and bladders, and van Leeuwenhoek's ideas about taste.

The letter of December 4, 1674, about the optic nerve and van Leeuwenhoek's technique of observing cerebral structures, was published the following year in volume 12 of Philosophical Transactions. The next three letters were all unpublished. On January 22, 1675, he wrote about his improved technique for viewing blood cells and sectioned brain tissue. Perhaps knowing his persistent observations of blood were a problem for the Royal Society, he added:

I can demonstrate to myself the globules in the blood as sharp and clean as one can distinguish with one's eyes, without any help of glasses, sandgrains that one might bestrew upon a piece of black taffety silk.

On February 11, 1675, he described salt crystals, vinegar eels, soap, pepper, bile, mustard, optical nerve, fish eggs, and leaf veins, among other things. On March 26, 1675, he described bean and pea meal. He continued his observation of blood serum, discussing the transparency of objects and how sap circulates and muscle has veins. He added:

You observe at people of great knowledge in Paris ... do not agree on the globules I have discovered. ... I do not mind this at all.

His letter of August 14, 1675, the only other letter published in volume 10 of Philosophical Transactions, continues his observation of the texture of blood and the parallel role of sap of plants. He also discusses the structure of sugar and salt and the difference in how they taste. In an unpublished passage, he adds:

You recommend me to call in the assistance of other persons, capable of judging said things.

His letter of December 20, 1675, describes live creatures in water as well as his technique for examining nerves and blood cells. He adds:

I looked forward to another letter to learn of the opinion of the Gentlemen on my thesis, for I expect to be contradicted since the speculations set forth ... will appear strange to some people. I will be greatly obliged if these objections are communicated to me.

I saw that Mr. Boyle had invented similar glasses and that the said gentleman had thought much farther than I did, ... which I admit is a very important question.

On January 22, 1676, he wrote in yet another letter unpublished during his lifetime:

I detected living creatures in rain water.

In his next letter, February 22, 1676, full of observations about hair, horn, and bone and also unpublished, van Leeuwenhoek wrote to Oldenburg:

I learned that Mr. Hooke spoke about the hair to you. I shall be pleased to learn about our differences. When I shall be better informed I am quite willing to give up my opinion and accept Mr. Hooke's view. Please give him my best regards.

His next letter, April 21, 1676, was published, the only one in volume 11 of Philosophical Transactions. He presented his observations about the vascular system of a thin section of a year-old sprig from an ash tree.

Monsieur Constantin Hugens of Zulichem was pleased to shew me the Comparative Anatomy of the Trunks of Plants, written by Doctor Grew, and told me, that he had very ingeniously and learnedly discoursed upon that subject; though I, by reason of my unskilfulness in the English Tongue, could have little more than the contentment of viewing the elegant Cuts.

Van Leeuwenhoek follows with over two pages explaining his diagram (see left), often comparing explicitly or implicitly, his observations to Grew's. He ends:

I beg your favour, Sir, to communicate this to Dr. Grew, with my service to him, and to inquire of him, whether he hath seen as well as I. ... An answer to which particulars I should be very glad to receive from the said Doctor.

When published later that year in Philosophical Transactions, Van Leeuwenhoek's explanation has twenty-seven numbered references within it, added by Grew, who supplied the Notes after van Leeuwenhoek's letter. The notes, running half again as long as van Leeuwenhoek's original description, respond in great detail, sometimes confirming, sometimes contradicting. While such detailed responses were common during meetings of the Society, I can find no other instance in the early Philosophical Transactions of an article with a detailed point-by-point response immediately following it.

At the end of the letter, between his observations of the ash sprig and Grew's response, is a paragraph about "some French Wine, ... which hath a very delicate taste." Van Leeuwenhoek continues:

In this wine I have divers times observed small living Creatures, shaped like little Eels. ... These creatures I have kept in my Study for a whole month swimming in Wine. And though they move strongly, yet they make but little way, whereof the cause may be, that they are quite destitute of leggs.

Grew's response is all about the ash sprig, nothing about the "small living Creatures".

On May 29, 1676, in yet another unpublished letter to Oldenburg discussing his sectioning techniques and observations about wood, among other things, van Leeuwenhoek added:

If I can be of service with my observations of wood and dissecting of it in the presence of learned Gentlemen ... by sending an attested report of what the Gentlemen saw, I will do so gladly.

At this point, only three of van Leeuwenhoek's dozen previous letters had been published. The letters to him from Oldenburg have not survived, but we can see from the letters that he was eager to engage other scientists and willing to change his ideas. In other words, he was open to the review of his peers.

We can also imagine how he pondered the fact that to this point, most of his interesting observations had not been published and would, as far as he knew, remain forever buried in a pile on Henry Oldenburg's desk. In fact, it would be another two hundred and fifty years before they would be published, in 1930.

On July 28, 1676, van Leeuwenhoek wrote a letter directly to Robert Boyle, about the effects of air on the chemical combination of ammonia and copper, responding to an article that Boyle had published in 1675 in volume 10 of Philosophical Transactions.

With the help of an English and Dutch dictionary (since I do not know the English language) I understood from Transaction Nr. 120 that you had put some copper-filings in spirit of salts etc. and since I had in my study spirits of sal ammoniac which served me for several observations I was eager to repeat your observations.

It is difficult to understand what was happening at the Royal Society during these years. The letters to van Leeuwenhoek are lost. Birch's History (vol III, pp. 88 and 143), filled with the Society's experiments and discussions, mentions Leeuwenhoek only twice in these years.

May 7, 1673:

Mr. OLDENBURG produced a book of Dr. de GRAAF dedicated to the Society, ... together with a letter to Mr. OLDENBURG, dated at Delft in Holland, 28th April, 1673, communicating some microscopical observations of Mons. LEEWENHOECK.

November 12, 1674:

Mr. OLDENBURG was desired to produce Mr. LEEWENHOECK'S observations concerning air, blood, &e.

We don't know whether van Leeuwenhoek's other letters were read or discussed; We don't know whether he was being ignored or rejected. We know only that few letters were published, and that was Oldenburg's decision. Grew's extraordinary response indicates a willingness to engage van Leeuwenhoek, but not about his "small living creatures."

We also know from van Leeuwenhoek's occasional comments that Oldenburg, at least, was pushing back and van Leeuwenhoek was searching for reasons why he was not being published.

He was, in any case, whether or not due to the reactions in London, continuing his observations of the little creatures in a more organized, systematic manner.

^

A Year's Wait
October 1676 - October 1677

While his publishing career had hit a dry spell, Van Leeuwenhoek continued conducting an extended series of observations and experiments with his animalcules. Perhaps someone else would have given up or stopped sending letters if they weren't going to get published. Instead, van Leeuwenhoek came on stronger.

He wrote his longest letter yet to Oldenburg on October 9, 1676; however, it would not be until the following spring that this letter was read to the members of the Society and extracts published in volume 12 of Philosophical Transactions later that year. It begins, repeating almost exactly words from his unpublished letter of January 22, 1676:

In the year 1675, I discovered living creatures in rainwater.

On October 30, 1676, van Leeuwenhoek sent a letter to Oldenburg thanking Grew and Boyle for paying attention to him. He added:

Sir, please be assured that I like to hear of objections on any matter I believe to be true, for objections are nothing but a reason to observe more accurately and to state most rigorously nothing but the base facts, but I don't like discourse on matters I doubt, therefore you and the Philosophers will oblige me by pointing out my errors.

After this point, Birch's History records that the Royal Society's meetings began to spend considerable time on van Leeuwenhoek's claims, specifically his long letter of October 9, 1676. On February 1, 1677, Birch reports:

There was read part of a very long letter of Mr. LEEWENHOECK to Mr. OLDENBURG, dated at Delft, 9th October, 1676, which had not been produced before, because it could not be sooner translated into English out of the Low Dutch language, in which it was written.

The contents thereof were a great number of observations made by Mr. LEEWENHOECK with his microscope, concerning certain little animals found by him in vast quantities in common water, snow-water, well-water, and such water. ...

It was ordered, that the sequel of these observations should be read at the next meeting; and that the author be desired to communicate his method of observing.

"Little animals" in "vast quantities". Two weeks later, on February 15, 1677:

Mr. OLDENBURG produced the sequel of Mr. LEEWENHOECK'S letter concerning the great plenty of very little animals observed in rain, well, sea, and snowwater, as also in water, in which pepper had lain infused.

The remainder of this paper was referred to another meeting; and the secretary was again desired to procure from Mr. LEEWENHOECK his method of observing, that by making use of the same, the Society might be enabled to confirm his observations.

The ability to "confirm his observations," to replicate results, is what we now call reliability of the evidence. Birch notes that the final part of van Leeuwenhoek's long October 1676 letter was read on February 22, 1677. Even extracted for publication finally the following year, this long letter ran to eleven pages in Philosophical Transactions. In all of volume 12, where most articles ran between two and five pages, only one other exceeded the length of this one by van Leeuwenhoek.

The next letter that van Leeuwenhoek wrote to Oldenburg is dated March 23, 1677, and it was read at the meeting of March 29, 1677. It was also the first that van Leeuwenhoek included in his self-published collected letters. Birch notes:

A letter of Mr. LEEWENHOECK to Mr. OLDENBURG, dated at Delft, 23d March 1677 was read, giving some account of his observing live animals in water.

In the March 23 letter, van Leeuwenhoek refers to two letters to him, now lost, of February 12 and 22, asking for information about his "method of observing". He proceeds to give it to them.

I was not a little pleased that my Observations about Water had not displeased your leaned Philosophers. Nor do I wonder, they could not well apprehend, how I had been able to observe so vast a number of living Creatures in one drop of water, that being very hard to conceive without an ocular inspection.

Objectivity. As Descartes' Discourse on Method instructs, van Leeuwenhoek was:

careful to avoid precipitancy and prejudice, and to comprise nothing more in [his] judgment than what was presented to [his] mind so clearly and distinctly as to exclude all ground of doubt.

Repeatedly in his letters, van Leeuwenhoek calls his speculations what they are and keeps them separate from his observations. The animalcules were as clear, van Leeuwenhoek wrote, as "sandgrains that one might bestrew upon a piece of black taffety silk".

Analysis. Descartes' second precept was:

to divide each of the difficulties under examination into as many parts as possible, and as might be necessary for its adequate solution.

Van Leeuwenhoek walks the readers through his procedure of dividing a thin glass pipe into sections and shows them his arithmetic.

This small quantity of Water I gather up into a very slender glass-pipe, dividing by this means that little water into 25 or 30 parts, of which I observe one part after another.

He concludes:

... and therefore 1000000 living Creatures in one drop of water. In which computation I rather lessen than heighten the number. ...

Yet I need not yield, that I ever do exaggerate my numbers.

Quantification. Descartes' final precept was:

And the last, in every case to make enumerations so complete, and reviews so general, that I might be assured that nothing was omitted.

Van Leeuwenhoek not only enumerated in the sense of counting. He sent drawings with almost all of his letters, and referred to them in the text. The members of the Royal Society could do the math, as much as it defied common sense.

This letter of March 23, 1677, was published in volume 12 in the number following, and thus a month or so later, the long letter from October 1676. At the end of the March 23 letter, van Leeuwenhoek adds a postscript of complaint that was not published:

Having again and again observed that you cannot find time to translate my letters in English.

After his early successes, he seemed to think that the problem was only one of translation. It seems more likely a question of validity and reliability. After the members heard van Leeuwenhoek's letter on March 29, Birch notes:

It was ordered, that Dr. GREW should be desired to try what he could observe in the like waters; and that for this purpose an extract should be given him by Mr. OLDENBURG of Mr. LEEWENHOECK'S observations formerly read to the Society.

On May 14, 1677, Van Leeuwenhoek wrote another letter to Oldenburg,

Yours of the 22th of February mentions, that some of your Friends did wish, I would with all possible exactness observe the Carneous Fibres of a muscle, and also the Cortical and Medullar part of the Brain.

Trying to be agreeable, van Leeuwenhoek does as requested, describing muscles and brains, moxa and cotton and his dissecting technique:

I took the flesh of a cow; this I cut asunder with a sharp knife, and using a microscope I severed before my eyes the membrane from it.

This letter has no mention of swarming little animalcules, but van Leeuwenhoek does insist on another very large number.

These globuls, of which I saw that the Carneous filaments do consist of, are so small, that, if I may judge by my sight, I must needs say, that ten hundred thousand of them would not make one grain of gravel-Sand.

This letter ends with an unpublished request to relieve what must have been his consternation over the reception he was receiving at the Royal Society:

I beg you to let me know in what respect my observations agree with or differ from those of others.

This letter, published in Philosophical Transactions volume 12 later that year, would turn out to be the final of van Leeuwenhoek's letters published by Oldenburg, who died on September 5, 1677.

Apparently, Nehemiah Grew, himself an accomplished user of the microscope, was not able to replicate van Leeuwenhoek's results. After Oldenburg's death, at the next annual election of Society officers, he and Robert Hooke were elected co-secretaries, replacing Oldenburg and Thomas Henshaw.

Hooke would continue in his unofficial position as Curator of Experiments. But who would replace Oldenburg, who had published Philosophical Transactions himself -- its founding editor and the person who paid for the printing out of his own pocket? (Philosophical Transactions did not become an official Royal Society publication until the 1753.)

On October 5, 1677, the unflappable van Leeuwenhoek sent another letter to the Society along with a cover letter to its president, Viscount Brouncker. Birch notes that at the next meeting, the first without Oldenburg, on October 15, 1677:

Mr. HOOKE read a letter, which had been delivered him by Mr. HENSHAW, to whom it was sent by the president, in which Mr. LEEWENHOECK understanding, that Mr. OLDENBURG was dead, desired to know, to whom he might address his letters for the future; including several testimonials of his former experiments, and an account both in Dutch and Latin of some new observations.

The consideration of this was adjourned to the next meeting. And in the mean time Mr. HOOKE was desired to make a microscope after a way, which he proposed as very likely to do as much, if not in the same manner as that of Mr. LEEWENHOECK.

This is the first mention of any Latin translations provided by van Leeuwenhoek. Philosophical Transactions going into a hiatus after Oldenburg's death, van Leeuwenhoek's "new observations" were published the following year by Robert Hooke in Microscopium along with a long response. (See Period 2.)

The "several testimonials" from ministers, a public notary, and "other persons of good credit" were no doubt appreciated, but they were irrelevant, perhaps redundant is a better word because of the success Hooke was about to have.

While we have no evidence of any reaction by van Leeuwenhoek, a quick summary reveals what may well have been a source of frustration.

By October 1674, van Leeuwenhoek had developed sufficiently strong and difficult-to-use lens to begin to see the world of microorganisms. Meeting initial skepticism, he independently performed an extended series of experiments and controlled observation, he made careful records, and he sent them in October 1676, with illustrations, to the Royal Society. It was a another whole year before the Society got around to "considering" his claims, and even then, they wanted to be able to see for themselves.

Could they have asked van Leeuwenhoek to join them? Could they have sent a delegation to Delft? Yes, but that's not how science was learning to work. The members of the Royal Society had to have someone else independently duplicate van Leeuwenhoek's results from scratch.

Fortunately, they had at their disposal probably the only person on earth capable of this feat of replication and verification: Robert Hooke.

Hooke's Three Tries
November 1677

Robert Hooke was a man of many interests. He had paid some attention to the microscope when he published his groundbreaking and best-selling Micrographia in 1665. Other events then occupied his time. He helped Sir Christopher Wren, another Royal Society charter member, rebuild London after the Great Fire of 1666. As Curator of Experiments for the Royal Society, he turned his mind to an wide array of scientific claims in what we now call physics, chemistry, and biology. For years, he devised experiments to replicate these claims at the Society's weekly meetings.

In November 1677, he turned his mind back to microscopy to do what Grew had not been able to do: show the members of the Society the vast number of little animals that van Leeuwenhoek was claiming to see.

First try: "no discovery made"

Birch reports on the meeting of November 1, 1677 (emphasis added):

There were produced a great many exceedingly small and thin pipes of glass of various sizes, some ten times as big as the hair of a man's head; others ten times less. These were made in order to try a conjecture of Mr. HOOKE, propounded to the Society, that the discoveries, affirmed to be made by Mr. LEEWENHOECK, were made by help of viewing with a good microscope such small pipes containing the liquor or water, in which those multitudes of exceedingly small insects or animals wriggling among each other are discovered;

for that he alledged, that the said pipes being filled with liquors became themselves as it were magnifying glasses, augmenting such bodies, as swim in the said liquor, on those parts of the said pipes, which are farthest from the eye-glass;

for the pipes themselves being looked on by the help of a very good microscope, are made very large and conspicuous; and they again augmenting the opposite parts by the refraction on their cylindrical surfaces double the effect of a single microscope, as was very evident.

But notwithstanding this there was no discovery made in the liquor, that was made use of, which was only common pump-water, of any such minute animals.

Using a single-lens microscope of the type he had described in Micrographia in 1665, the same design that van Leeuwenhoek used, and using the glass pipe to effectively double the magnification, this lens apparently did not have the resolution nor did the room provide the visibility. "There was no discovery made."

It was therefore ordered, that against the next meeting pepper-water should be provided, and some better microscope than that made use of, that the truth of Mr. LEEWENHOECK'S assertions might, if possible, be experimentally examined.

Second try: "nothing could be seen"

A week later, at the meeting of November 8, 1677, Birch reports that Hooke had a new, improved experiment:

The first thing exhibited was the experiment charged on Mr. HOOKE at the last meeting, of examining pepper-water with better microscopes and thinner and small pipes. The fabric of the microscope for holding such pipes was new and more convenient and expeditious for such examinations than the usual forms, consisting wholly of pieces, which slid any ways very easily, and would stand fixed and steady in any posture, and admit light to the object every way:

by the comparing of which various ways of inlightening the object one might the more easily and certainly discern the true shape and constitution of any body.

The lens, the positioning, the lighting, it was all improved.

But notwithstanding the pepper-mixture was very strong, being made of rainwater and whole black pepper steeped in it for two or three days; and notwithstanding the microscope was much better than that shown at the last meeting; yet nothing of Mr. Leeuwenhoek's animals could be seen.

As it turned out, Hooke was getting interested in microscopy again.

Mr. HOOKE suggested same farther improvement of that instrument by making use of the convexity of the surface of the liquor itself (put upon the plates of Muscovy glass) for augmenting the body within the liquor; as also for augmenting the body beyond it.

Over the next six months, Hooke would continue his investigations, including a detailed response to van Leeuwenhoek, in Microscopium, the second part of his book Lectures and Collections, published in 1678.

Third try: "there could be no fallacy"

At the next meeting a week later, Hooke was back for another try. On November 15, 1677, Birch records:

The first experiment there exhibited was the pepper-water, which had been made with rain-water and a small quantity of common black pepper put whole into it about nine or ten days before. In this Mr. HOOKE had all the week discovered great numbers of exceedingly small animals swimming to and fro.

This time, he let the pepper steep longer and he had successfully seen the little animals before the meeting.

They appeared of the bigness of a mite through a glass, that magnified about an hundred thousand times in bulk; and consequently it was judged, that they were near an hundred thousand times less than a mite. Their shape was to appearance like a very small clear bubble of an oval or egg form; and the biggest end of this egg-like bubble moved foremost.

A hundred thousand was more a sense of an order of magnitude than an actual measurement, but van Leeuwenhoek's claims were now credible.

They were observed to have all manner of motions to and fro in the water; and by all, who saw them, they were verily believed to be animals; and that there could be no fallacy in the appearance.

In an interesting choice of words, they were "believed" AND their appearance was "no fallacy". The whole process had led to this moment of replication. Birch continues:

They were seen by Mr. HENSHAW, Sir CHRISTOPHER WREN, Sir JOHN HOSKYNS, Sir JONAS MOORE, Dr. MAPLETOFT, Mr. HILL, Dr. CROUNE, Dr. GREW, Mr. AUBREY, and divers others; so that there was no longer any doubt of Mr. LEEWENHOECK'S discovery.

These men, (see details on right) would not take van Leeuwenhoek's word for it. They would not take the word of van Leeuwenhoek's credible witnesses. They had to see for themselves. Birch concludes by noting what many useful experiments do; they suggest new experiments.

Notice was ordered to be taken of this discovery, and further trial was desired to be made upon rain-water alone; and upon rain-water, in which had been steeped, wheat, barley, and other seeds and grains: as also that blood and several other liquors should be after the same manner examined.

Manipulate the variables. Try rainwater alone; try other infusions. In addition to water, try blood. Over the next six months, Hooke would do all that and more. And he would publish a book about it, Microscopium.

Science was new, but it was alive and well and in good hands with Robert Hooke and the Royal Society.

Glass Pipes

These glass pipes were discussed in the letter that van Leeuwenhoek wrote to Henry Oldenburg on June 1, 1674.

Below left, a pipe for viewing blood and milk. Right, pieces of that pipe to stick to the pin behind his lens.

In his letter of June 1, 1674, van Leeuwenhoek explained how he used the pipe above to view cow brains.

"A B (See Fig. IV.) is a hollow Glass-pipe, A C is of the thickness of a coarse horse hair. Its end from A to D, I thrust into the white of the Brain (having first open'd it with a Pen-knife,) and to the open end B, I apply my mouth, and there suck as strongly as I can, and during that suction I move the pipe by thrusting it inward and drawing it outward, so that the point A remains still moving in the white matter of the Brain:

"By which means I got a little of that part of the Brain into my Glass-pipe, which I view in the manner above-prescribed in the account of blood."

"I have formerly sent you my way of seeing the motion
of the Globuls in the Crystallin liquor of the Blood: Having
since contrived a more convenient Glass-pipe for that purpose,
I cannot but give you and your Curious Friends notice thereof;

"See Fig. V. A B is a hollow Glass-pipe from B to 0, about the thickness of a coarse horse-hair; from 0 to D, about the thickness of a Pigeons-quil, and the thickness from D to A somewhat slenderer. 'Tis open on both its ends, A and B: Into this pipe I brought some Blood."

Letter XXVIII

to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practitioner of medicine at the very renowned academy at Leiden
September 28, 1716

Dutch title: Waarneemingen op den Cocos-boom.

English title: Observations on the coconut tree.

Letter XXVIII of September 28, 1716 to Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practitioner of medicine at the very renowned academy at Leiden Van Leeuwenhoek's summary of the contents: Observations on the coconut tree. The straw, the reed, etc. have only ascending vessels. All of our inland wood growth, so much as it is known to the writer, also has horizontal vessels. For what purpose? Every year a new little bark grows on trees. The horizontal vessels also give the stiffness to the trees. The reed, the straw, etc., provided with joints instead of horizontal vessels. The coconut tree also has joints, as do several other Indian trees. The Bambodian Peak tree has no horizontal vessels. Observations concerning the wood of a coconut tree. Vessels in the hairy parts of the rind. Between these parts again lie other parts that also have vessels. Hard bark that covered the hairy parts. The bark is described. The coconut tree receives its growth from the so-called rind. Round globules from the rind going inwards; probably in order to transport the rising sap from the bark inwards. In the trunk of the coconut tree is no hollow part, as the writer had expressed before this. Great usefulness of the coconut tree provides for the human race. How obliquely the limbs on trees run that have no horizontal vessels. The obliqueness gives greater stiffness to the coconut tree. Few branches on the same tree. Various ascending vessels indicated in the coconut tree. Smaller and larger vessels, that are together made out of thread-like parts. The large vessels are enclosed in sheaths. The little sheaths do not lie in order. The thread-like parts, lying next to the bark, are thinner that those lying inwards. The little threads are in turn composed of even smaller threads, that are hollow. The bladder-like parts cut through. Wood from a Curaçaoan coconut tree examined and described. Extraordinary hardness of the same wood on the outer side. The same between the bark and the wood also has hair-like parts. The coconut trees appear to get their thickness from the barks, quite different from what happens in our trees. This last wood also cut through and placed before the magnifying glass. The bladderlike parts cut through lengthwise, and inspected in the same way. The large vessel of the coconut tree is also composed of ring-like parts: and long spiraling parts continue on from there. The spirals in the mentioned vessels were investigated and indicated. Explanation of the spiraling. The same found in the largest vessels of the straw. How useful the spiraling is in order for the saps, that are in the vessels, to be transported upward. Observations concerning a coconut. Long thread-like parts in the rind of the coconut followed up. The thread-like parts may better be called vessels. A section of the rind of the coconut shown. No other thread-like parts are nourished in the bark of the coconut, as are none from the nut and the bark itself. The outermost little sheath or skin of the bark of a coconut depicted. The coconut gets its nourishment and full development from the vessels that are called threads. Eye-like parts in the nut. How the little plant in the coconut is nourished. The coconut opens its bark not at the time of its full development: different from how it is with many other seeds. The innermost parts of the mentioned rind shown. Spiraling parts in the inner vessels of the same rind. The inner sheath of the bark has countless little vessels. This sheath brought before the magnifying glass. An inexpressible multitude of small parts, whose use is unknown. A section of a coconut shown, etc. Again shown that the so-called hair-like parts are nothing other than vessels. Shape of the little vessels. The sap of the coconut is very nutritious. Observations made concerning the same. Abundant little vessels in the pit of a coconut. Smallness of the little vessels. The same pit is made of little pipes, which are described. Oil enclosed in the pipes. The part, that the writer had witnessed in front of the plant, is shown. The same cut into slices, in which, as they dried, a little gap showed itself. It was found that the part, which was witnessed in front of the plant, was not part of the plant; but was by itself wound around the plant. Various parts of the coconut depicted, and shown to the reader. The plants, cut lengthwise, shown in various figures. In a plant, that was neatly cut in the middle, no root, tree, and leaf could be distinguished. The plant, not lying in the middle of the coconuts, was a sign that they were already grown. Description of the plant, closed up in the coconut, and indication of its parts. The coconut is also a seed of a tree; just as an almond, peach, plum, etc. The hard barks of the last have seams in order to expand when fully grown: the coconuts do not: and thus must the full growth of the coconuts happen in another manner. The benefits that the coconut tree, as also the date tree, bring to the human race. The whitish material depicted that lies inside against the bark of the coconut.	Letter XXVIII of September 28, 1716 to Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practitioner of medicine at the very renowned academy at Leiden Van Leeuwenhoek's summary of the contents: Waarneemingen op den Cocos-boom. Het Stroo, het Riet, enz. hebben maar opgaande vaten. Doch al ons inlandsch Hout-gewas, voor zoo veel 't den schryver bekent is, heeft ook horizontale vaten. Waar toe de laatste dienen? Alle jaren groeyt 'er een nieuwe bastje aan de Boomen. Die horizontale vaten geeven ook de styfte aan de Boomen. Het Riet, het Stroo, enz. met leden voorzien, in plaats van horizontale vaten. De Cocos-boom heeft ook leden, gelyk ook eenige andere Indiaansche Boomen. De Bambodiaassche Piek boom heeft geene horizontale vaten. Waarneemingen omtrent het hout van een Cocos-boom. Vaten in de hairachtige deelen van de Schorsse. Tusschen die deelen leggen weer endere deelen die ook hunne vaten hebben. Harde bast die de hairachtige deelen bekleedt. Die bast word beschreven. De Cocos boom geniet zyn aanwassinge uyt de zoogenaamde schorse. Rondachtige bolletjes uyt de schorsse binnewaart gaande; waarschynlk om de opgevoerde sappen uyt de bast binnewaart te voeren. In den stam van den Cocos-boom is geene holligheyt, gelyk de Schryver voor dezen geoordeelt had. Groote nuttigheyt die de Cocos-boom het menschelyke geslagte verschaft. Hoe schuyns dat de leden om de Boomen loopen, die geene horizontale waten hebben. Die schuynsheyt geeft grooter styfte aan den Cocos-boom. Weynige takken aan den zelven Boom. Verscheyde opgaande vaten in den Cocos-boom aangewezen. Kleynder en grooter vaten, die 't zamen een draadachtig deel uytmaaken. De grootachtige vaten zyn met vliesjes omvangen. Doch die vliesjes leggen niet op order. De draatachtige deelen, naast de bast leggende, zyn dunder dan die binnewaarts leggen. De draatjens bestaan weder uyt draatjes, die hunne holligheden hebben. De blaasachtige deeltjes doorsneden. Hout van een Kurassouwschen Cocos-boom onderzocht en beschreven. Ongemeene hardigheyt van 't zelve hout aan de buitenste kant. Het zelve tusschen de bast en 't hout ook bezet met hairachtige deelen. De Cocos-boomen schynen hunne dikte te bekommen uyt de basten, recht anders als in onze boomen geschiedt. Dit laatste hout ook doorsneden, en voor het Vergroot-glas geplaatst. De blaasachtige deeltjes in hunne lengte doorsneden, en op de selfde wyze bezigtigt. De groote Ader, ofte 't groote vat, van den Cocos-boom bestaat ook uyt kringsgewyze deeltjes: en vervolgens uyt lange omwentelende deelen. Die omwentelingen der gemelde vaten worder nagespeurt en aangwezen. Uytlegging van die omswentelinge. Het zelve bevonden in een der grootste vaten van het Stroo. Hoe dienstig de omwenteling is om se sappen, die in de vaten zyn, opwaart te voeren. Waarnnemingen omtrent een Cocos noot. Lange draatachtige delen in de schorsse van de Cocos-noot nagezocht. Die draatachtige deelen mogen beter vaten genoemt worden. Een gedeelte van de schors van de Cocos-noot vertoond. Geene andere draatachtige deelen in de bast van de Cocos-noot, als de geenen waar uyt de noot, en de bast zelf, gevoedt worden. Het opperste vliesje of huydje van de bast van een Cocos-noot afgetekent. De Cocos-noot geniet haar voedzel en Wasdom uyt de vaten die men draaden noemt. Oogswyze deelen in de Noot. Hoe het plantje in den Cocos-noot gevoedt word. De Cocos-noot opent haare bast niet ten tyde van haaren wasdom: ander als het met veele andere zaaden gaat. De binnenste deelen van de gemelde schorsse vertoont. Omwentelende deeltjes in de binnenvaatjes van dezelve schorsse. Het binnenvlies van de bast met ontelbaare vaatjes bezet. Deze vlies voor het Vergroot-glas gebragt. Onuytsprekelyke menigte van kleyne deeltjes, welker gebruyk onbekent is. Een gedeelte van een Cocos-noot vertoont, enz. Wederom getoont dat de zoogenoemde hairachtige deeltjes niet anders zyn als vaten. Maakzel van die vaatjes. Het sap van de Cocos-noot is zeer voedzaam. Waarnemingen omtrent het zelve gedaan. Menigvuldige vaatjens in de pit van een Cocos-noot. Kleynte van die vaagtjens. Dezelve Pit bestaat uyt pypjens, dewelke beschreven worden. Oly in die pypies besloten. Het deel, dat de Schryver voor de plant aangezien had, word vertoont. Het zelve in schyfjens gesneden, in dewelke, als ze gedroogt waren, zich een gaatje vertoonde. Word bevonden dat het deel, 't welk voor de plant aangezien was, de plant niet en was; maar alleenlyk een omwindzel van de plant. Verscheyde deelen in de Cocos-noot afgetekent, en den leezer vertoond. De planten, in de lengte doorsneden, vertoonden zich in verscheyde figuuren. In eene plant, die net in 't midden doorsneden was, wierd getoont het geen de Wortel, de Boom, en de Bladen zal uytmaken. De plant, niet in 't midden van de Cocos leggende, was een teken dat ze al aan 't groiyen was geweest. Beschryving van de plant, in de Cocos-noot opgesloten, en aanwyzing van haare deelen. Cocos-noot is ook een zaad van een Boom; zoo wel als een Amadel, Perzik, Pruym, enz. Doch de harde basten van de laatste hebben naaden om zich ten tyde van Wasdom uyt te zetten: de Cocos-noot niet: en dus moet de wasdom in de Cocos-noot op een andere maniere geschieden. Voordeelen die de Cocos-boom, gelyk ook de Dadel boom, aan 't menschelyk geslagt toebrengt. De witachtige stoffe, die van binnen tegen de bast van de Cocos-noot leyt, afgetekend.
English     ||    Nederland Van Leeuwenhoek's summary of Letter XXVIII
Figure 1: small piece of coconut wood showing the joints that draw nearer and farther from each other Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 1
Figure 1: small piece of coconut wood showing the joints that draw nearer and farther from each other Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 1
Figure 2: cross-section of coconut tree showing the large vessels rising obliquely to give the trunk its stiffness Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 2
Figure 3: cross-section of coconut wood from close to the bark showing hollow threads within hollow threads surrounded by bellow-like parts Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 3
Figure 4: lengthwise section of coconut wood through the bellow-like parts Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 4
Figure 5: lengthwise section of one of the bellow-like parts Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 5
Figure 6: section of spiraling vessel from coconut tree shown at T in Figure 2 Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 6
Figure 7: rind of a coconut cut away, showing the nut Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 7
Figure 8: section of rind showing vessels Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 8
Figure 9: lengthwise section of the sheath or outermost skin that lies against the rind of a coconut Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 9
Figure 10: section of the hard rind of a coconut showing a vessel composed of smaller vessels Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 10
Figure 11: a coconut cut away Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 11
Figure 12: cross-section at W in Figure 11, showing the six-sided tubes filled with oily globules Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 12
Figure 13: section of the pit of a coconut at its thinnest Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 13
Figure 14: cross section of pit taken at E in Figure 13, showing bark along the lower edge and vessels filled with oil Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 14
Figure 15: section cut at G in Figure 13 with lower part transporting fluids downwards and upper part transporting them upwards. Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 15
Figure 16: section cut through the middle with lower part transporting fluids downwards and upper part transporting them upwards. Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 16
Figure 17: a similar section showing dried part at the top Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 17
Figure 18: section of white material inside the hard rind of the coconut showing the spiraling parts Letter XXVIII to: Den Heer Herman Boerhave. A.L.M. Philosoph: en Medic: Doctor; Professor der Kruyd-kunde, en Praktyk der Medicyne in de seer Vermaarde Academie te Leyden - philosopher and medical doctor; professor of herbal knowledge, and practicioner of medicine at the very renowned academy at Leiden September 28, 1716 Dutch title: Waarneemingen op den Cocos-boom. English title: Observations on the coconut tree. Letter XXVIII Figure 18

Letter XXX

to: Den Heer Godfried Willem van Liebniz, etc.
November 17, 1716

Dutch title: Uyttreksel uit het schrift van de heer Pauli wederlegt.

English title: Summary of the writing of Mr. Pauli refuted.

Letter XXX of November 17, 1716 to Den Heer Godfried Willem van Liebniz, etc. Van Leeuwenhoek's summary of the contents: Summary of the writing of Mr. Pauli refuted. One can examine in animals whether conception happens through an egg. That will never be found. The little animals in the male seed are living. The author has many times shown this to different gentlemen. What the use is for the multitude of little animals. The milt of a cod pours out in one year more living little animals, than there are people living on the face of the earth. The little egg of a female cod mixed with the seed of a male cod: what follows next. The little animals, in the male seed of the cod, are not larger than those found in the male seed of the smelt. The large multitude of the little animals compares to the abundant seeds of the trees, that also do not all grow into full trees. This appears still more clearly in the currant tree. Also in the strawberry. Mr. Naboth, from Leigzig, answered. The little worms in the male seed are not dead but living little animals. The same have a form in the male seeds, and of the same size. However, there are some differences in the tail of the little worms, close to the body. Male and female in the seed are distinguished. Honorable testimony by the certainly learned gentleman given to the writer. The uterus, Fallopian tube, the little mouths of the Fallopian tube, and the imagined egg nest are indicated in order to refute the common opinions. The so-called eggs also investigated. Never has the author seen that such an egg was thrust so far out of the so-called egg nest by nature, that half protruded outside the strong membrane of the egg nest. Whereby some have probably been threatened; and have intended to see a sucked-off egg. It is not understood how such an egg can be transported in the tube and though the tube in the uterus. The movement in the tube, in order to transport something in the uterus, is also not understood. And other opinions refuted; to know that the little animal which is found in the male seed, truly is the creature from the animal; but only is placed on or in an egg. The answer to the question, why the egg nest would be made. The male animals also have parts, that appear unnecessary. How long the little animals would be able to live in the seed ball.	Letter XXX of November 17, 1716 to Den Heer Godfried Willem van Liebniz, etc. Van Leeuwenhoek's summary of the contents: Uyttreksel uit het schrift van de heer Pauli wederlegt. Men kan wel in de dieren onderzoeken of de ontfankenis geschiet door een Ey. Dat zal noit bevonden worden. De diertjens in het mannelyk zaad zyn levendig. De Auteur heeft dit menigmaal aan verscheydene Heeren getoont. Waar toe de menigte van die diertjens dienstig is. De hom van eenen Kabeljauw stort in een jaar meer levendige diertjes uyt, als 'er menschen op den aardbodem leven. Het eytje van een Kabeljauw wyfje vermengt met het zeed van een Kabeljauw mannetje: wat daar opgevolgt is. De diertjes, in het mannelyk zaad van de Kabeljauw, syn niet grooter als die in het mannelyk zaad van de Spiering gevonden worden. De groote menigte van de diertjens toegepast op de menigvuldige zaaden der Boomen, die ook niet alle tot Boomen opwassen. Dit blykt nog klaarder in een Aalbesie Boom. Ook in de Aarbeyen. De Heer Naboth, te Leipsich, beantwoordt. De wormtjes in 't mannelyk zaadd zyn geen doode maar levende diertjes. Dezelve zyn in de mannelke zaaden van een maakzel, en van dezelve groote. Echter is 'er eenig onderscheid aan de staart der wormtjes, dicht aan het lyf. Mannetjes en wyfjes in het zaad zyn onderscheyden. Loffelyke getuigenis door zeker geleerd Heer aan den schryver gegeven. De Baarmoder, Tuba Fallopiana, de mondekens van de Tube Fallopiana, en het gewaande Eyer-nest worden aangewesen, om het gemeen gevoelen te wederleggen. De zoogenaamde Eyeren ook doorzocht. Noit heeft de Auteur gezien dat zoo een Eye zoo verre uyt het zoogenaamde Eyer-nest door de natuur gestoonten was, dat het ten halve buyten de sterke Membrane van het eyernest uytpuylde. Waar door sommige waarschynlyk bedrogen zyn geweest; en gemeent hebben een afgesogen Ey te zien. Het is niet te begrypen hoe dat zoo een Ey in de Tuba, en door de Tube in de Baarmoeder, kan gevoert worden. De beweeginge in de Tuba, om iets in de Baarmoeder te voeren, is ook onbegrypelyk. Een ander gevoelen wederlegt; te weeten dat het diertje, 't welk in 't mannelyke zaad gevonden word, waarlyk het schepzel is van het dier; maar dat het aan of in een Ey word gesplaatst. Antwoord op de vragt, waar toe het Eyer-nest gemaakt zoude zyn. De mannelyke dieren hebben ook wel deelen, die onnoodig schynen. Hoe lang dat de diertjes in de zaad-bal zouden konnen leeven.
English     ||    Nederland Van Leeuwenhoek's summary of Letter XXX
Figure 1: sheep's uterus showing Fallopian tubes Letter XXX to: Den Heer Godfried Willem van Liebniz, etc. November 17, 1716 Dutch title: Uyttreksel uit het schrift van de heer Pauli wederlegt. English title: Summary of the writing of Mr. Pauli refuted. Letter XXX Figure 1
Figures 2 and 3: sheep's "egg nests" or ovaries Letter XXX to: Den Heer Godfried Willem van Liebniz, etc. November 17, 1716 Dutch title: Uyttreksel uit het schrift van de heer Pauli wederlegt. English title: Summary of the writing of Mr. Pauli refuted. Letter XXX Figures 2 and 3

Witnesses

According to Birch's History, Hooke's replication of van Leeuwenhoek's observations were witnessed by nine named members and "various others". The two most historically prominent, Christopher Wren and Nehemiah Grew, are mentioned elsewhere on this web. In addition:

Thomas Henshaw
1618-1700
Founder Fellow of the Society

Sir John Hoskins, Bart
1634-1705
fellow 1674
president 1682-1683
also spelled Hoskyns

Abraham Hill
1633-1721
Founder Fellow 1663
secretary 1673-1675
treasurer 1679-1700

John Mapletoft
1631-1721
clergyman and physician
Fellow 1676
member of council 1677, 1679, 1690, and 1692

Jonas Moore
1617-1679
mathematician, surveyor, Ordnance Officer and patron of astronomy
Fellow 1674


William Croone
1633-1684
physician
Founder Fellow 1663
nominated van Leeuwenhoek for election as Fellow in 1680
also spelled Croune

John Aubrey
1626–1697
antiquary and writer
Founder Fellow 1663