Wrote Letter 30 of 1680-04-05 (AB 57) to Robert Hooke about the testicles and sperm of a rat and organisms in the gills of oysters and in the sap of vines

Date:

April 5, 1680

Standard reference information

Cole's number:

AB/CL number:

AB/CL volume:

Text of the letter in the original Dutch and in English translation from Alle de Brieven. The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren.

The original manuscript on three quarto pages, written and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1881. L 1. 52).

Leeuwenhoek's summary

From both printings of Levende Dierkens and translated into Latin for all of the editions, some re-titled, of Anatomia Seu Interiora Rerum.

Ontledingen en ontdekkingen, Van de Testicul van een Rot, ende Dierkens in deselve; Van de Mossel en Oester; Van Levende Dierkens in het sap dat uit een Wyngaard-rank droop.

Dissections and discoveries, of the testicle of a rat, and little animals in the same; of the mussel and oyster; of living little animals in the sap that dripped from a vineyard shoot.

Reception in London

Five days after the letter was written, according to Birch's History (vol. IV, p. 32), it had been received in London and read at the April 1/10 (O.S./N.S.) meeting:

Mr. Leewenhoeck's letter to Mr. Hooke, who had translated the sense of it into English, was read, giving an account of some farther discoveries of his about the eel-like worms in the seed of a rat; as also of the motion of the gills of muscles, oisters, &c.

It was ordered, that these should be examined at the next meeting, in order to which Mr. Hunt was directed to procure some oisters and muscles.

There is no indication in Birch's History that Mr. Hunt followed up.

Specimens and methods

"Everything in water shows bigger than outside it."

Leeuwenhoek was aware of the additional magnification that his lenses got from a glass tube:

The reason why I caused it to be drawn hanging in water is that the filaments hang better separated thus than without water, and so can better be distinguished, especially if one allows the light of a candle to shine through the glass. But knowing that everything in water shows bigger than outside it, we must not take the filaments to be as thick as they are drawn here.

This additional magnification may have been what Leeuwenhoek referred to as the method he did not tell anyone about. See the Related page under Learn more below.

He did not get very far with the observations of vine sap. The letter ended with a reference to one of his two gardens, this one within Delft's city walls.

After this, I went to my garden, which lies within this town, and there also observed the sap dripping from the vine but could not discover any living creatures in it, except only a little worm that was uncommonly big, compared with the other living little animals.

I thence went to my garden outside the town and there too observed the sap from divers vines, but could not discover any living creatures in it. I cut off two pieces from vine-shoots to make them drip the more and went to examine the sap again the next day, but could not find in it anything living. I took a new glass bottle and caught the sap in it, and carried it home and examined it, and again could not discern any living little animals in it.

I am now busy finding out if possible, why there are living little animals in one sap and none in the other.

It took Leeuwenhoek two months to answer his question. Letter 31 of June 14, 1680, described and illustrated the little animals that he found in the sap.

The public and their opinions

"It appears impossible even to myself."

Leeuwenhoek made an attempt to counter commonsense opposition to his observations. He tried a human-scale analogy that would help his readers visualize the motion that he could not have drawn.

And when now and then I imagine how exceedingly great the number of animalcules is, it appears impossible even to myself; but then, when I return to such observations, as I repeatedly did a few days ago, I cannot but say that I am not mistaken in what I tell, or when I say that when these little animals would swim from one side of the fiber to the other, they would comparatively cover a greater distance than our cows do when they go from one side of their enclosed meadows to the other.

Figures

The figures of a rat's testicle in a jar of water and a little animal that came from it were the only two figures illustrating this letter. The originals were in ink and are preserved in the Royal Society's archives. In the text, these figures appeared together on a separate unnumbered plate in both the Dutch and the Latin editions. The scans on the left sidebar are from the 1686 first edition of Levende Dierkens.

Leeuwenhoek wrote in the letter that he drew Figure 1 "as far as it was feasible to me" (so veel het mij doenlijk was). He had someone else draw the far more complex Fig. 2 for him: "I caused it to be drawn" (ick heb laten afteijckenen).

Publication history

Related sources, especially Philosophical Transactions, and first editions only of Leeuwenhoek's volumes of letters. For later editions see Related events under Learn more.

Year	Author	Title
1665	various	Philosophical Transactions
1686	Leeuwenhoek, A. van	Levende Dierkens
1686 - 1718	Clerc, J. le, and J. C. de la Croze	Bibliothèque universelle et historique
1687	Leeuwenhoek, A. van	Anatomia Seu Interiora Rerum
1693	Leeuwenhoek, A. van	The Abstract of Two Letters Sent Some Time Since by Mr. Anth. Van. Leeuwenhoeek to Dr. Gale and Dr. Hooke
1948	Leeuwenhoek, A. van	Alle de Brieven. The Collected Letters. Volume 3

Other publications:

In 1686, Jean le Clerc summarized this letter in Bibliothèque universelle et historique, but did not include these figures.

Thirteen years after Leeuwenhoek wrote this letter and seven years after he published it in Levende Dierkens, it was published in Philosophical Transactions (vol. 17, no. 196). They made a different plate from the same drawing, still in the possession of the Royal Society.

Learn more

Period 2 - 1679-1686

Additional magnification

Structure of the letters in Period 2

1680: Member of the Royal Society

Specimens: Sperm

Related people:

Robert Hooke

Related locations:

Dr. Schaepmanstraat

Related events:

Date	Event
June 25, 1664	Bought a garden outside the walls of the city
April 11, 1680	Robert Hooke read Letter 30 of 1680-04-05 about rat sperm and organisms in gills of oysters and sap of vines
January 1, 1686	Published Levende Dierkens (Living Animals), Letters 28 - 31, 34 - 36
January 1, 1687	Published Anatomia Seu Interiora Rerum (Interior Anatomy), 19 Letters from 28 - 52
December 29, 1693	Sold the garden outside the walls of the city
January 1, 1696	Published Arcana Naturae Microscopiorum (Nature's Mcroscopical Mysteries), 19 Letters from 28 - 52 (2nd)
January 1, 1696	Published Levende Dierkens (Living Animals), Letters 28 - 31, 34 - 36 (2nd)
January 1, 1708	Published Arcana Naturae Microscopiorum (Nature's Mcroscopical Mysteries), 19 Letters from 28 - 52 (3rd)
January 1, 1722	Published Opera Omnia, seu Arcana Naturae Microscopiorum (The Works, or Nature's Microscopical Mysteries), 25 Letters from 28 - 60 (4th)

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Letter 30 Figures

Wrote Letter 30 of 1680-04-05 (AB 57) to Robert Hooke about the testicles and sperm of a rat and organisms in the gills of oysters and in the sap of vines

"Everything in water shows bigger than outside it."

"It appears impossible even to myself."

Figures

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