Wrote Letter 37 of 1683-01-22 (AB 70) to Christopher Wren

January 22, 1683
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Leeuwenhoek's summary

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.

Ondervindingen en Beschouwingen Der onsigbare geschapene waarheden, Waar in gehandeld werd Vande Eyerstok, ende derselver ingebeelde Eyeren, dat een Mensch uyt een Dierken voort komt, vande samen stremminge, Saden in een Boom, hoe een Dierken in 't Saad van een Haan, Cabbeljaau &c. 't Vlees uyt de Borst en Poten van een Vloy, Testicul, Respiratie, en Wormkens uyt de Eyeren vande Vloy, Vlees uyt de Poten van Vliegen, Sal-volatile Oliosum met Bloed vermengt, geen gistinge in 't Bloed ende de makinge van het selfde.

Experiences and considerations of the truth of invisible creation wherein is treated the ovary, and the same ovary imagined, that a person comes forth from a little animal, of the congealing of the same, seeds in a tree, how a little animal in the seed of a cock, cod, etc. The flesh out of the breast and legs of a flea, testicule, respiration, and the little worms from the ovary of a flea, flesh from the legs of flies, sal volatile oliosum mixed with blood, no fermenting in the blood and the making of the same.

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 eighteen quarto pages, written and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1896. L 1. 67). The seven drawings are lost.


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.

Plate from
Arcana Naturae Detecta

Figures 5 - 7

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.