Letter, from Antoni van Leeuwenhoek to Francis Aston, dated at Delft Signed autograph Dissection of a lens of a human's eye and lens of other animals; function of eye-lids and the involuntariness of blinking; observations of the cornea of pig and ox; observations of the optic nerve; concerning the skin of the Moors Original figures now no longer exist Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 4, p 209 English extract printed in 'Philosophical Transactions', vol 14, no 165, p 780 14 April 1684