An Extract of a Letter from Mr. Anthony Van Leeuwenhoeck, F. R. S. Dated October the 12th. 1713. Concerning the Fibres of the Muscles, &c.

Leeuwenhoek, A. van
Philosophical Transactions of the Royal Society
29, no. 329, pp. 55-58
Royal Society

The extract referred to in the title is from Leeuwenhoek's letter of 1712-11-08 (AB 296) to Anthonie Heinsius, the first letter in the Send-Brieven. A year later on 1713-10-12, Leeuwenhoek sent a copy to Philosophical Transactions editor Hans Sloane, which explains the date in the Philosophical Transactions title as well as the first paragraph, which does not exist in the version Leeuwenhoek published as the first letter in Send-Brieven.

The Philosophical Transactions translation by John Chamberlayne is interesting to compare to the one in Alle de Brieven / Collected Letters. If the letter in Send-Brieven was the one Leeuwenhoek sent to the Royal Society, then Chamerlayne's translation is significantly less precise. His translation was published in Philosophical Transactions v. 29 no. 329, probably in Spring 2014, though the official date of v. 29 is January 1, 1714 (right sidebar; click to enlarge).

Leeuwenhoek's letter, about muscles in whales as well as in other fish, oxen, and mice, was immediately followed not by another letter but by an article (right sidebar) in which an unnamed writer, probably Philosophical Transactions editor Edmond Halley, summarized the work of Wijer Willem Muys (1682-1744), a professor of medicine at the university in Franaker, Friesland. Muys had found that blood left the arteries and spread through the hollow muscle fibers and was then collected in the veins to return to the heart. Muys noted that his findings, supported by microscopic observation, were contrary to Leeuwenhoek's.

That summary is preceded by:

To these Observations of Mr. Leewenhoek I shall join,

III. An Extract from the Journal Literaire, Publish'd at the
Hague, for the Months of January and February, 1714.
Pag. 238. Being,

An Account of several Observations concerning the Frame and Tex-
ture of the Muscles; By Mr. Muys of Franequer.

The Celebrated Mr. Muys, who always acts for the Honour of the Academy of Franequer, and Advantage of Students in Physick and Anatomy, has made several Discoveries, as to the Mechanism and Texture of the Muscles of Animals; of which these are some.

That "I" in "I shall join" must be the journal's editor, Edmond Halley. The preceding letter by Leeuwenhoek was the only letter by Leeuwenhoek published during Halley's six years as editor of Philosophical Transactions. It wasn’t just Leeuwenhoek. Halley was not interested in publishing any biological topics. The index to Volume 29, which Halley edited, shows a scant six articles under anatomy, what we would now call biology, and all the rest of the articles under topics of interest to Halley, from astronomy to geometry to the earth's meridian lines.

Why publish it at all? This one Leeuwenhoek letter and the summary of Muys following it came in Halley's second number. Perhaps it had been left to him by the previous editor, Hans Sloane, who may have been a few numbers into v. 29 before Halley took over.

By the time Leeuwenhoek wrote Letter XXIX of 1716-11-05 (AB 328) to Herman Boerhaave a few years later, he must have read the article following his in Philosophical Transactions. He took exception to this passage:

[Muys] injected a coloured Liquor by the same Artery [of a lamb]; and then not only the small Arteries appeared filled with this tinged Liquor, but he found also that the Liquor past thro' each Fibre, either in a Serpentine manner, or undulating, or frameing several Angles, or joined by a great number of Anastomoses.

He observed also, that many small Branches of the Arteries which before could not be seen, appeared visibly, spread all round the little Fibrillae, and tinged with the same Colour.

In the letter to Boerhaave, Leeuwenhoek responded:

Some years ago I saw that a certain Doctor Medicinae says in his writings that the blood circulates through the little fibres of flesh; and also that a Professor in an adjacent Province wanted to maintain this as well. In order to prove this he says that for this reason flesh is red.

These are silly arguments, for if they would merely look at the flesh of calves, flesh of fowls, flesh of turkeys, etc., which is always white, this should, then, also be red, according to their thesis. Briefly, they err greatly.

It's an open question whether Halley added the Muys article in the interests of dialogue or to undercut Leeuwenhoek with the work of an academic authority. It's also interesting that Leeuwenhoek responded to Muys in a letter to Boerhaave and not to the Royal Society, where it probably would have been published in Philosophical Transactions.


Since Professor Muys lived in Franeker, which had the only university in Friesland, an “adjacent province” might be Groningen.

Maty's Index has an extra entry here for AvL but the TOC of that volume gives Mr Muys as the author.