Wrote Letter L-568 of 1721-01-24 to the members of the Royal Society about vessels in wood from Ambon (Indonesia), oakwood, and pinewood, the muscle fibres of a cow, a whale, and a mouse, and the structure of a red blood cell

January 24, 1721
Standard reference information
Collected Letters volume: 

The letter is written in Dutch in an unknown hand. Only the signature and the postscript are written by Leeuwenhoek himself. The writer may have taken dictation from Leeuwenhoek, but he probably made a fair copy of Leeuwenhoek’s manuscript. In any event, the writer/copyist used very few capital letters, his punctuation did not distinguish a comma from a period, and he did not start a new paragraph very often. For the sake of readability, the translated text in Collected Letters, vol. 20, is divided into full sentences, the punctuation is modernized, and the paragraphing follows the text as printed in Philosophical Transactions. The same copyist also wrote Letter L-576 of 13 June 1722.

The letter was read a year later, after James Jurin was elected second secretary and editor of Philosophical Transactions on 30 November 1721 O.S., during the 11 February 1722 O.S. meeting of the Royal Society.