Wrote Letter L-070 of 1678-03-18 to Nehemiah Grew about sperm in other animals and what Harvey and de Graaf got wrong about reproduction

March 18, 1678
Standard reference information
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. Collected Letters, vol. 2, p. 325 erroneously lists this letter as appearing in Philosophical Transactions, vol. 12, no. 142.

The original manuscript on seven folio pages, written and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1862. Early Letters L1.34). An English translation is Early Letters L1.35.

An excerpt in English was published in Philosophical Transactions, vol. 12, no. 140, pp. 1003-05, dated 31 August 1678. (This article is not noted in Collected Letters, vol. 2, p. 324 and 325.) Another extract, about sperm, in Latin, was published as the third part of an article in no. 142, p. 1044, that began with an excerpt from Letter L-061 of November 1677 on pp. 1040-43, continued with a note from editor Nehemiah Grew on p. 1043, and concluded with excerpts about sperm from Letter L-073 of 31 May 1678 on pp. 1045-46. See Publication history below. 

Leeuwenhoek wrote this letter to Nehemiah Grew about:

  • the sperm of dogs, rabbits, fish
  • a discussion about fertilisation and the views of Regnier de Graaf and William Harvey; what they got wrong
  • defends and further formulates his animalculistic conception of fecundation
  • the vessels in semen
  • female reproductive organs in cows and lambs

At the end of the letter, a passage indicates that Leeuwenhoek's lab was not portable. Perhaps the instruments he refers to are things like clamps for his microsopes, to keep them still and free his hands.

My only chance lies in using the sperm that the animals may drop now and again after copulation, which I must use at once without loss of time lest it should change into a watery matter. I hardly see my way to do this as I require my customary seat and instruments, which I cannot place everywhere for use. If I could manage to do so I do not doubt that I should see as numerous vessels as I discovered in the case of human semen.