Wrote Letter L-034 of 1676-02-22 to Henry Oldenburg about hair, cow skin, horn, and bone, inviting Hooke's response

February 22, 1676
Standard reference information
Leeuwenhoek's number: 
Collected Letters number: 
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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 nine folio pages, written and signed by Leeuwenhoek, with a smaller inserted sheet of ink drawings, is preserved at the Royal Society (MS. 1846. Early Letters L1.17).

Leeuwenhoek wrote this letter to Henry Oldenburg about:

  • An account of the structure of hair and how it grows
  • a theory about curly hair and a refutation of Johan van Beverwijk's opinion on the structure and growth of hair
  • the structure of cow's skin; the membranes of eggs

He wrote about hair in direct response to Oldenburg's request. At the end of January, Leeuwenhoek had written

I also have written down my speculations on the reason why one hair curls, another hangs down, and how we imagine to see a cavity in the hair of any animal. If you want to see the drawing of two hairs with the roots, I will send it to you.

In early February, Oldenburg replied that he -- and Robert Hooke -- did indeed want to hear about Leeuwenhoek's observations of hair, so Leeuwenhoek sent this letter right away.

Oldenburg's Letter L-032 was dated February 3 in London, which was February 13 in Delft. Allowing eight days for delivery, Leeuwenhoek received it around February 21. This response, then, was written, or at least dated, the following day.