Wrote Letter L-122 of 1683年01月22日 to Christopher Wren about the function of the ovary, muscles of insects, drinking tea and mild beer, erythrocytes, and a theory on the formation of blood

From both printings of this letter, first in 1684 by Gaesbeeck in Eyerstok, which was sometimes bound with Letter 39, and then by itself probably in 1696 by Boutesteyn and translated into Latin for Arcana Naturae Detecta.

Two weeks after this letter was written, it was produced at a meeting of the Royal Society (Birch's History, vol. IV p. 178, 180):

Sir Christopher Wren produced a letter to himself from Mr. Leeuwenhoek, written at Delft 22 January 1683; which was ordered to be translated against the next meeting.

It was read at the February 7/17 (O.S./N.S.) meeting:

The translation of Mr. Leeuwenhoeck's letter to Sir Christopher Wren of January 22, 1683 was read, concerning generation from an animalcule, not an egg; the muscles of a flea, and its testicles, the worm and nympha, the sting and wings of a gnat, and its feathers; the alteration made in the blood by sal volatile oleosum.

Leeuwenhoek addressed this letter to Christopher Wren after having written since 1679 only to Robert Hooke and a couple of letters to Thomas Gale. Leeuwenhoek began, referring to Letter 36:

In a letter dated the 4th of April 1682 (addressed by me to Mr. Robert Hooke) I have written about the structure of the muscle of the shrimp and the lobster and afterwards I wrote to that gentleman on July 28th 1682 in which latter missive I asked to be informed whether my figures respecting the anatomy of wood, sent to the Royal Society on January 12th 1680, will be published in print, as Mr. Hooke at one time wrote to me they would. Not having received up till now a reply to either letter, I take the liberty to address these trifling observations to you.

A few paragraphs later, he elaborated:

The late Mr. Oldenburg has not sent me the Philosophical Transactions after Nr. 137.

No. 137 had been published in volume 12 in 1677. For almost a year, then, a newly elected member of the Royal Society, Leeuwenhoek had not received any letters from them. For five years, he had not received any copies of Philosophical Transactions even though extracts of Letters 22, 24, and 25 had been published in numbers 140 and 142.

At the end of the letter, he wrote:

Before this I compared this coagulation with the globules in beer in my letter dated June 14th 1680, addressed to Mr. Thoman Gale, Secretary of the Royal Society. Up till now I have not seen this letter published in the Philosophical Collections.

It is not surprising that a year after Leeuwenhoek wrote this letter, Daniel van Gaesbeeck in Leiden began published complete, not extracted, letters in Dutch, not English. Gaesbeeck's dedication to that volume supports the roots of Leeuwenhoek's motivation in his dissatisfaction with the fate of the work he had entrusted to the Royal Society.

"Maggots ... carried in a box in my pocket"

In this letter, Leeuwenhoek mentioned the well from which he obtained some of his specimens as well as water to compare with the water from other sources: canals, ponds, and the North Sea.

This autumn there was an extraordinary multitude of gnats in my little summer-house. I imagined they came from the well which is in its neighbourhood.

This was the same well he mentioned in Letter 10 of February 11, 1675 and Letter 18 of October 9, 1676. The location of his summer house is not clear but it may have been in the garden he had outside of town.

This Letter 37 was the first letter in which Leeuwenhoek noted that he carried live specimens on his body to keep them warm.

This summer I have taken great pains to find out how much time the maggots from the eggs took to become fleas. Several times I had maggots in four days from eggs which I carried in a box in my pocket. I have tried to rear these maggots, but in spite of all my pains, I have not succeeded in keeping them alive longer than to the age of 12 days.

Note: In Letters 56, 57, and 59 from the summer and fall of 1687, Leeuwenhoek also described how he and his wife carried silkworms, beetles, and more maggots on their bodies.

Letter 37 also had a short narrative about Leeuwenhoek's own body.

An important part of Leeuwenhoek's process was how he used evidence to not only make up his mind, but to change his mind. He noted:

Yet I well remember that before now I wrote to the late Mr. Oldenburg similar things (and forwarded them to him) about strings lying intertwined in sperm, an opinion which I now unconditionally reject, having found that this intertwining was merely accidental.

In spite of many comments he made to the contrary, he seemed to think that other people were as rational.

I know quite well that some people would take their oath on having found the supposed eggs in the tuba fallopiana. ... I also imagine that if a so-called egg should be found in the tuba fallopiana immediately after copulation and should be examined closely, the prevailing opinion would be abandoned.

On the other hand, because he found the parts of plants inside their seeds, he expected to find parts of animals inside the little animals. Here he commented on humans.

And why, seeing that the womb or tuba fallopiana is as it were an entire world in comparison with a little animal in male seed, ... cannot we imagine that ... its skin will serve for afterbirth and that the inner body of the little animal will assume the figure of a human being, already provided with a heart and bowels, and indeed having all the perfection of man.

This letter consisted of observations occasioned by the writing of three other researchers and a conversation with a physician. The first was unnamed by Leeuwenhoek but was noted by Alle de Brieven / Collected Letters as a reference to Regnier de Graaf's Een nieuw ontwerp van de ledematen der vrouwen, tot de voort-teelinge dienstig, which he had in the year before his death published in Latin under the title De mulierum organis generationi inservientibus (title page on right).

Having read a certain book, edited by a physician of this country and dealing with human procreation, in which the author writes at great length about the ovary of woman (as it is now called), I once more took the ovaries of a number of lambs, now about a year old, and fattened a few months in a stable this winter. These lambs rut every month, but no rams serve them. And I imagine that if anything could be said about the so-called ovaries of woman, those of quadrupeds could serve just as well.

In addition to responding to his old friend De Graaf, he was also involved with Cornelis 's Gravesande and the other physicians in the group portrait that Cornelis de Man painted the previous year. By demonstrating it in their presence, he could have been referring to one of the Wednesday afternoon meetings in the Theatrum Anatomicum.

This so-called ovary I have not only studied by myself, but have also demonstrated it in the presence of a certain learned Anatomist and other learned gentlemen and have there adduced the reasons why I cannot imagine why so many learned men agree with, and adhere to, the opinion that the tuba fallopiana sucks off or pulls off an egg from the ovary and transmits it through such a narrow channel as I showed the tuba fallopiana to have, the more so because the supposed eggs, that is to say the largest in the ovary, were as big as peas, nay, some as large as an entire ovary, mostly consisting of glandular parts, full of blood-vessels and so tightly enclosed in membranes that I was not able to tear off with my nails one of these so-called eggs.

Second, he responded to a false charge made about him in a book that the editors of Alle de Brieven / Collected Letters have not been able to identify.

Third, he had a conversation with a local physician, unnamed, but they were discussing a remedy prescribed in several books at the time.

A certain physician told me that many people suffering from fever were entirely cured after having taken Sal volatile oleosum, because Sal volatile oleosum makes the blood very quick and thin. So I resolved to mix the Sal volatile oleosum with blood, in order to discover, if possible, its action on blood.

Fourth, he responded to a book that Alle de Brieven / Collected Letters identifies as Nieuwe beginselen tot de genees- en heelkonst, published in 1681 by Heydentryck Overkamp (title page on right).

A few days ago a certain booklet, recently published, fell into my hands, in which a physician of this country proclaims that there is fermentation in our blood, just as batter is made to rise by yeast, salt, and eggs; also that the fermentation is caused by the air which acts upon our blood, especially in the lungs and is mixed with it.

But to me it is inconceivable that air-bubbles are made in the blood. ... If there had been air-bubbles in the blood, though a thousand million times smaller than a grain of sand, I should certainly have discovered them in the numerous observations of the blood and the globules contained in it which I have made in the course of 11 or 12 years.

"Why are there so many thousands of little animals in one drop?"

Leeuwenhoek seems to have discussed his observations with other people in Delft. In this letter, he responded to two of their questions. Why are there so many little animals in male seed? and Why don't women produce many children at one birth?

And the second question:

Figures

The original drawings are lost. The Dutch and Latin editions that Leeuwenhoek published used the same plates with all eight figures. The figures were placed in the text where Leeuwenhoek discussed them, except for Figs. 5 - 7, which appeared on one plate in the text. The one below (click to enlarge) came from page 37 of the 1695 first edition of Arcana Naturae Detecta, as did the images on the sidebar.

In the text, Leeuwenhoek did not say who drew Fig. 1. He noted that he drew Fig. 2 himself.

Once more I have taken the testicles of a flea, this time with less difficulty. I have put them before a microscope and drawn them as best as I could. In fig. 2 ABCD is the testicle; AF and DE are sperm-vessels that carry unto and carry down.

He noted that all of the other figures were drawn by someone else. He instructed that person to distort what he saw in order to emphasize what Leeuwenhoek wanted to direct the reader's attention to.

I caused these to be drawn as in fig. 3. A gnat's wings are also furnished with feathers which I have also caused to be drawn. Fig. 4 is a wing of a gnat, as it appears to the naked eye. In fig. 5 ABC I had the wing drawn on a larger scale in order to show that not only the entire circumference of a gnat's wing is covered with big and smal feathers as in fig. 6.

These original drawings were lost, so we do not know how the figures were arranged. When the plates were prepared for printing in 1684, Fig. 4 was engraved on the same plate as Fig. 3 and inserted into the text on page 14 of Eyerstok. However, Fig. 4 did not relate to Fig. 3. It was the life-size version of the feather in Fig. 5, which appeared on a plate with Fig. 6 and Fig. 7 that was inserted into the text on the following page 15. It would have made more sense to group the life-size and enlarged images on the same plate so that their relative size could be more easily compared.

Two months after Leeuwenhoek wrote this letter, it was excerpted in Philosophical Transactions, vol. 13, no. 145, dated March 10, 1683.

It was also published in September 1684 (not August, as in Alle de Brieven / Collected Letters vol. 4, p. 2) in Nouvelles de la republique des lettres on pages 646 to 653, without any figures.

After Leeuwenhoek's death, in 1766 an extract from the Philosophical Transactions excerpt was published in Collection académique. Vol. VII pp. 47-48, also without any figures.

Leeuwenhoek wrote of the toedraagende and afdraagende vessels, which Alle de Brieven / Collected Letters translated as "afferent" and "deferent", scientific terms not common until two centuries after he wrote this letter.