Wrote Letter L-544 of 1716-11-05 to Herman Boerhaave about the size of sperm from rams, cod, and ling, little animals from rain water and soil, and blood in arteries and veins

Date:

November 5, 1716

Standard reference information

L-number:

L-544

Leeuwenhoek's number:

XXIX

Collected Letters volume:

Text of the letter in the original Dutch and in English translation in Alle de Brieven / The Collected Letters is not yet available at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren.

The original manuscript is lost.

Continuing his research disproving spontaneous generation, Leeuwenhoek investigated the size of sperm and their occurrence in the epididymis of a ram as well as the number of spermatozoa in the soft roe of a cod and a ling. To learn more about how the sperm could generate so quickly, Leeuwenhoek turned to microbes from rain water and soil and their multiplication. Responding to another researcher, Leeuwenhoek affirmed that arteries and veins have an opening only near the heart. There is no blood outside of blood vessels.

He begins by responding to Boerhaave's question from a previous letter.

Your Honour asks me whether I have seen a difference in the size of the little animals in the male seed of animals.

Leeuwenhoek's summary

Leeuwenhoek's inhoudsopgave, summary of the contents, for Send-Brieven XXX. My translation and emphasis.

Of 'er onderscheyd van grootte in de diertjes van't mannelyk zaad te bekennen is. Onbedenkelyk getal van zulke diertjes in 't mannelyk zaad gezien. Volwassene en onvolwassene diertjes in 't zelve zaad. Of dezelve diertjes in de zaad-ballen voortteelen.

De diertjes, in 't mannelyk zaad van een Ram gezien, zwommen allemaal eenen weg; de eene achter de anderen.

Grootte van de hom der Kabeljaauwen en Lengen, waar uyt de diertjen voortkomen. Een groote Kabeljauw loost wel zoo veel zaad, in den tyd van eene maand, als 'er zoude konnen gaan in de holte van eenen hoed. De Membrane van de hom, als 'er het zaad uyt is, krimpt toe: doch is het naastvolgende jaar volder van diertjes als het voorgaande. Waar door het geschiedt dat 'er zoo veele milioenen van diertjes in de hom voortkoomen.

Water-diertjes, die den geheelen winter op een komtoir gelegen hadden, zwemmen weer door het water. Diertjes uyt het water op het land gevoert door den wind. Diertjes, die de winterkoude niet konnen verdraagen, sterven evenwel niet uyt: en waarom?

De mannelyke zaaden, en de Kuyt-greynen, of Eyeren, zyn zoo groot in de kleyne vischjes, als in de grootste van dezelfde soort.

Diertjes in het regenwater gevonden. Hoe sterk dezelve vermenigvuldigden. Deze sterke vermenigvuldiging aan de zaad-ballen toegepast.

De Arteriën en Venen, of de aders en slag-aders, hebben geene opening als in het Hert. Hoe het voedzel uyt dezelve in de deelen des lichaams gestooten word. Hoe de Bloed bolletjens, in groote benauwtheyt, ongemeene beweginge, enz. door de rokjens geperst worden. Het is niet waar dat het bloed door de vleesfibertjens circuleert, of ommeloopt.

Whether there is any difference discerned in the size of the little animals in the male seed. Unbelievable number of such animals seen in the male seed. Fully grown and not fully grown animals in the same seed. Whether those little animals breed in the seed balls.

The little animals, seen in the male seed of a ram, all swam away, the one behind the others.

Size of the milt of cod and ling, where the animals originate. A large cod discharges as much seed in a month as could go into the hollow of a hat. The membrane of the milt shrinks when the seed is out of it, but the next year is fuller of little animals than the previous one. That is why it happens that so many millions of little animals come into the milt.

Water creatures, after lying in my comptoir all winter, swim through the water again. Little animals leave the water for the land conveyed by the wind. Little animals that could not tolerate winter cold, however, do not die: and why?

The male seeds, and the grains of hard roe, or eggs, are as large in the small fish as in the largest of the same species.

Little animals found in the rainwater. How substantially they multiplied. This substantial multiplication applied to the seed balls.

The arteries and veins have no opening as in the heart. How the nourishment is thrust from the same into the parts of the body. How the blood globules are pressed through the walls in great tightness, unusual movements, etc. It is not true that the blood circulates through the flesh fibers.

Specimens and methods

epididymis of a ram

soft roe of a cod and a ling

microbes from rain water and soil

Calculations

Leeuwenhoek wrote out this math in both words in the text and numbers in a footnote to p. 289 of Send-Brieven.

These little animals had procreated so much in a few days that I stood amazed at it.

I was eager to know how this multiplication came about. Eventually I have observed that these little animals did not live longer than 30. or 36 hours. Then they attached themselves to the glass and were motionless. Soon afterward, its body burst asunder and lay divided into eight little parts, which were in truth little animals, for after five or six seconds some of them swam away.

Now if a little animal produces 8. young, and each young little animal in its turn produces eight young, then after a period of nine days, two hundred and sixty-two thousand, one hundred and forty-four little animals would come forth from one little animal. If we observe this in the waters, who knows, then, how things go on in the seed balls of animals and in the soft roe of fishes.

Visitors to his house

I have shared the letter with Mr Abraham van Bleyswyk, Medicinae Doctor. Thereupon, Mr van Bleyswyk has partially dissected a male rabbit at my house. He will inform Your Honour about that which has been observed with regard to this.

I have put the moisture that came forth from the epididymis during the cutting-through before the magnifying glass in the presence of Mr Abraham van Bleyswyk, ...
After these little animals lying on a glass died, I spread them out thinly and viewed them many times on several successive days.

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
1714	Leeuwenhoek, A. van	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.
1718	Leeuwenhoek, A. van	Send-Brieven
1719	Leeuwenhoek, A. van	Epistolae Physiologicae
1965	Belloni, L.	Leeuwenhoek, Boerhaave und Bleyswyk über Spermatozoën
2024	Leeuwenhoek, A. van	Alle de Brieven. The Collected Letters. Volume 18

Notes

As part of his tendency to favor native Dutch words over foreign imports, Leeuwenhoek uses both in his summary, the foreign terms followed immediately by the Dutch terms.

blood vessels: De Arteriën en Venen, of de aders en slag-aders

circulate: circuleert, of ommeloopt

In the text of this letter, he uses Venae italicized as a Latin word and Arteritjens unitalicized and with a Dutch diminutive ending.

Learn more

Period 6 - 1712-1719

Related people:

Herman Boerhaave

Abraham Cornelis van Bleyswyk

Related events:

Date	Event
September 1, 1716	Visited by Hermaan Boerhaave, Frederik Ruysch, and Abraham van Bleiswijk
October 10, 1716	Herman Boerhaave wrote Letter L-541 to Leeuwenhoek in response to Letter L-540 about coconuts

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Wrote Letter L-544 of 1716-11-05 to Herman Boerhaave about the size of sperm from rams, cod, and ling, little animals from rain water and soil, and blood in arteries and veins

Life in Holland

in the 1600's