Letter, from Antoni van Leeuwenhoek to Hans Sloane, dated at Delft Signed autograph Observations of blood circulation in flounder; on red blood corpuscles of flounder and salmon, their oval form and the way they change shape to pass through capillaries; on blood vessels; observations of the sperm of a young cock No original figures attached Read to the Royal Society on 17 July 1700 English translation see EL/L3/18 Transcribed in JBO/10/192 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 13, p 131 English translation printed in 'Philosophical Transactions', vol 22, no 263, p 552 9 July 1700