Wrote Letter L-116 of 1682-03-03 to Robert Hooke about muscle fibres, hair, the cell nucleus in the erythrocytes of fishes, the liver of salmons, beards of oysters, and the structure and growth of oyster shell

Date:

March 3, 1682

Standard reference information

L-number:

L-116

Leeuwenhoek's number:

Collected Letters number:

Collected Letters 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 eleven quarto pages, written and signed by Leeuwenhoek, is preserved along with seven drawings at the Royal Society (MS. 1894. L 1. 66.).

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 het Vlees, ende groote menigte van kleine Vlees musculen van seer kleine Aaltjens, van de Vis, van 't Hair, van de Oesters en den selver Schulpen, enz.

Dissections and discoveries of flesh, and the great multitude of little flesh muscles of very small eels, of fish, of hair, of oysters and of their shells, etc.

Reception in London

Eight days after Leeuwenhoek wrote this letter, it had been received by the Royal Society and read at the March 1/11, 1682 (O.S./N.S.) meeting (Birch's History, vol. IV p. 132, 135, 530):

Mr. Hooke produced a long letter from Mr. Leeuwenhoeck, containing an account of several curious observations and discoveries made with a microscope by himself. The letter being in Low Dutch was not read; but Mr. Hooke having translated half of it read it to the Society, wherein was an account of several curious discoveries relating to the fibrils, hair or small claws of muscles. He promised to translate the remaining part of this letter against the next meeting.

Hooke did as he promised:

Mr. Hooke brought in the translation of Mr. Leeuwenhoeck's letter, which he read and explained some parts of it, and gave an account of what observations he had himself formerly made about the fibrils of muscles, their smallness, and form much like a chain of beads or a necklace of pearl; and he remarked, that he had several times written to Mr. Leeuwenhoek to desire him to inquire farther concerning the nature of muscles.

Mr. Hooke was desired to answer this letter of Mr. Leeuwenhoeck, and to send him the Philosophical Collections, that had been printed, and to publish this letter in the next Collections.

He did so, and four years later, Jean Le Clerc published a summary of the letter in Bibliothèque universelle et historique. That occasioned the discussion at the April 6, 1687, weekly meeting of the Royal Society.

It was ordered, that Mr. Hunt provide some oisters, to see, whether in a microscope there could be found any such animalcula, as are reported to be in the liquor of oisters from a letter of Mr. Leeuwenhoeck printed in the Bibliotheque Universale.

Specimens and methods

"A deft hand will require all its dexterity."

At the beginning of this letter, Leeuwenhoek confirmed his commitment to the methods of Francis Bacon, empiricism and inductive reasoning:

I have in the past often said that, if I found that I was mistaken in my opinion I would publicly confess my error. The case now is that I often imagined that I could distinctly see that the fleshy fibres of which the greater part of a muscle consists were composed of globules, and it appeared to me that this was distinctly visible when I observed the flesh-fibres through an ordinary microscope after I had cut them across and pulled them asunder crosswise with a fine needle. Thirdly it appeared to me that the rings or wrinkled contractions in each separate fibre of the flesh were globules.

He went on to discuss his dissection of muscle fibers, which consisted of similar thinner fibers. He continued to see globules in other substances.

Fig. 1 is a flesh-fibre in which frequently the rings and wrinkles became apparent to me, such as ABCD and others close to them as at EFGH and also IKLM; and so (as I have said before) they looked like globules when seen through an ordinary microscope.

If by "ordinary" he meant a lens with less magnifiying or resolving power, then "globules" was his catch-all term for objects that lay just beyond his ability to see.

He did not see any logical contradiction between his inductive reasoning and his assumption of a first mover, as he exclaimed later in the letter.

We see that the Creator is so wonderful and incomprehensible in combining the parts of his creatures, we are the more amazed as we penetrate deeper into the mysteries of his creatures.

Leeuwenhoek revealed very little about the specific techniques he used to prepare his specimens. In this letter, he explained what the problem was, but concealed his exact technique with "a deft hand".

If now any gentleman lover of learning should feel inclined to continue my observations, I would recommend him not to try this in hot, dry weather, but rather in damp and misty weather, for if, after having separated the minute membranes from the flesh-fibers, one takes a fiber to a clean place in order to split it, a deft hand will require all its dexterity to prevent the moisture from evaporating, causing the filaments composing a flesh-fiber, owing to their thinness, to dry up into a single, firm and clear substance - and perhaps in most cases bad success will follow.

In this letter, Leeuwenhoek mentioned his horse for the second letter in a row:

In the month of May I rode my horse, a mare, very hard over 4 or 5 miles

Response to other researchers

Leeuwenhoek frequently responded to the ideas of both the uninformed public and the supposedly well-informed experts. He did not usually name the person, but in this case, Alle de Brieven / Collected Letters makes an accurate identification of Stephen Blankaart's De nieuw hervormde anatomie.

My only purpose in inserting in this place my calculations of the flesh-fibres - which a certain physician in our country calls flesh-threads - was to bring out their minuteness; the more so because this gentleman tries to state as a fact that these flesh-fibres are implanted in the mouth of the vena, and that they end in the arteries; also that the circulation of the blood passes through these fibres; nay, he maintains that he has seen that there are valves in them, and that he made these observations not by means of a microscope but with the naked eye, evidently having taken an entire minute muscle for a fiber.

Leeuwenhoek stated the problem and what he saw as a probable cause. He responded with three different calculations (see below).

Calculations

How small are muscle fibers?

Leeuwenhoek's simple arithmetic showed that the fibers were much too small for Blankaart to see with his naked eyes.

Once more I have taken the flesh of oxen and cows on several days. I concluded that the flesh-fibers are so thin that if 50 of them are put side by side they cover 1/22 of an inch. If you take only 1/20 of an inch and leave the rest for the very small membranes which envelop the fibers, this will come to 1000 flesh-fibers for the length of one inch, that is to say 1.000.000 flesh-fibers enveloped in their membranes in one square inch.

If now we assume that every 200 of these flesh-fibers, enveloped by their membranes, form a little muscle of flesh, 5000 of these little muscles will go to a square inch.

Next, he calculated a human-scale comparison.

I have also compared the thickness of the flesh-fibers with the thickness of a hair from my wig and considered that 4 flesh-fibres taken by me from the diaphragm of an ox, near the ribs, could only be the thickness of a hair; and I judged that a hair from my beard be 9 times thicker.

Having set that up, he could invoke an ancient Greek authority to support these "astonishingly large" (verwonderens groot) numbers.

So there are 200 filaments in the circumference of a flesh-fiber, and because this number of filaments composing it is so astonishingly large, I cannot omit making a calculation in this place. In order to calculate the surface area of a circle if we know the circumference, Archimedes teaches us that 88 gives 7, which then gives the square number of the circumference.

He showed the calculation in the text and concluded that it:

... yields 3181 filaments as the contents of one fish-fiber. Who can realize such an incomprehensible number of filaments in one fish-fiber and who can tell whether each of these 3181 filaments may not be furnished in its turn with membranes and contain an incredible number of filaments.

Figures

The Dutch and Latin editions that Leeuwenhoek published used the same plates placed in the text where he discussed the figure. The scans on the left sidebar came from the 1708 third edition of Arcana Naturae Microscopiorum. The scans on the right sidebar show the original seven drawings preserved by the Royal Society.

In the text, Leeuwenhoek indicated that he drew these figures in red chalk. Referring to Fig. 2, he wrote:

I made a drawing of it as best as I could (for I cannot draw).

A few pages later, he wrote:

And if I had drawn fig. 4 according to the size that I observed constantly, it should have been more than 16 times thicker.

When he described what we now know as the nucleus of the blood cell, he wrote:

It seemed to me that some of them enclosed in a small space a little, round body or globule, and at some distance from this body there was round the globule a clear ring and round that ring again a slowly shadowing contour, forming the circumference of a globule and, as well as I could, represented in fig. 5.

The oyster shell, not included in the printed versions, was the most technically demanding of these drawings. Leeuwenhoek does not explicitly state that he drew it himself. Nor does he say that he had it drawn by someone else.

Comparison of the drawings and the prints on the sidebars shows how the engraver's skill improved the look of the drawings, though perhaps not their accuracy.

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
1678	Blankaart, S.	De nieuw hervormde anatomia
1679 - 1682	Hooke, R.	Philosophical Collections
1682	Leeuwenhoek, A. van	An account of several curious Discoveries ... made by Mr. Anth. Leuwenhoek with Microscopes
1683	La Roque, J. (ed.)	Journal de médecine
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
1754 - 1787	Berryat, J. (ed.)	Collection académique
1756	Birch, T.	The History of the Royal Society of London
1948	Leeuwenhoek, A. van	Alle de Brieven. The Collected Letters. Volume 3

Other publications:

Other publications

Immediately after receiving this letter, Robert Hooke published most of it and six of the figures in Philosophical Collections, number 5 for February 1682, pp. 152-160.

The following year, Jean-Paul de la Roque published part of this letter on pp 203 - 219 of the May 1683 issue of the short-lived Journal de médecine. He included four of the seven figures.

In 1686, Jean Le Clerk published an excerpt with none of the figures in Bibliothèque universelle et historique vol. 2, pp. 466-469.

After Leeuwenhoek's death, in 1755 Jean Berryat published excerpts in French translation in Collection académique, vol. II pp. 552-556.

Notes

Leeuwenhoek often used the word globulen, which is not in the Dutch dictionaries of the time. The Woordenboek der Nederlandsche Taal notes that it is an obsolete word meaning a more or less spherical piece of organic material. The only three citations are from Leeuwenhoek letters in 1670.

Alle de Brieven / Collected Letters translates Heeren Liefhebbers as "naturalists" with a footnote: beoefenaren der natuurwetenschappen (practicing the natural sciences).

Naturalist in this sense was a rarely used word before the end of the 18th century.

Sewel's 1735 dictionary translates it as "a Lover, also a Lover of learning or arts."

In this letter, Alle de Brieven / Collected Letters translates comptoir as "study", which is closer to an accurate description than some of the translations in other letters, for example "closet".

Learn more

Period 2 - 1679-1686

Structure of the letters in Period 2

1681-82: Hooke's Philosophical Collections

Related people:

Robert Hooke

Related events:

Date	Event
December 1, 1681	Robert Hooke wrote Letter L-115 of some time in December 1681 to Leeuwenhoek about his previous letters
February 1, 1682	Philosophical Collections number 5 published in London, including Leeuwenhoek's Letter L-116 of 1682-03-03 to Robert Hooke
March 11, 1682	Robert Hooke read the first part of Letter L-116 of 1682-03-03 about striated muscle fibres of mammals and fishes
March 18, 1682	Robert Hooke read part of Letter L-116 of 1682-03-03 about muscle fibers
April 22, 1682	Robert Hooke showed the Royal Society part of a flesh muscle in a microscope, but the rimples mentioned by Leeuwenhoek could not be seen
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
January 1, 1696	Published Levende Dierkens (Living Animals), Letters 28 - 31, 34 - 36 (2nd)
January 1, 1696	Published Arcana Naturae Microscopiorum (Nature's Mcroscopical Mysteries), 19 Letters from 28 - 52 (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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Wrote Letter L-116 of 1682-03-03 to Robert Hooke about muscle fibres, hair, the cell nucleus in the erythrocytes of fishes, the liver of salmons, beards of oysters, and the structure and growth of oyster shell

"A deft hand will require all its dexterity."

How small are muscle fibers?

Figures

Other publications

Life in Holland

in the 1600's