Leeuwenhoek did not publish any letters after 1718 in book form with his own summaries. The summary below comes from Alle de Brieven / Collected Letters.
In this letter, L. observes the structure of fat particles in sheep, lamb, flatfish, and perch. By melting the fat, he finds numerous veins and membranes in it.
Signed autograph letter. The manuscript is to be found in London, Royal Society, Early Letters L.4.77; 7 quarto pages.
A contemporary English translation of the letter by John Chamberlayne is found in Londen, Royal Society, Early Letters L.4.78; 7 pages.
The letter was read during the 21 June 1722 meeting of the Royal Society; Royal Society, Journal Book, vol. 13, p. 208; Letter Book Original, 15.75.
The original drawings are lost.
