Letter, from Antoni van Leeuwenhoek to Robert Hooke, dated at Delft Signed autograph Analysis of a hog's bristle; discussion of shedding hair; observing blackheads; examination of Leeuwenhoek's faeces when he had diarrhoea; discussing micro-organisms in human faeces, and several other animals; examining the structure of clay; the possibility that a blood transfusion can cure gout Four figures of hog's bristle are in red chalk Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 3, p 345 4 November 1681