Letter, from Antoni van Leeuwenhoek to Thomas Gale, dated at Delft Signed autograph Observations of beer whilst it ferments; microscopic observations of yeast; observations of the formation of carbonic acid; experiments with micro-organisms will reproduce in infused pepper-water kept in hermetically-sealed tubes (this led to the discovery of bacteria in general and the existence of anaerobic bacteria) Three figures - two red-chalk figures of yeast cells and one of a glass tube for determining the presence of micro-organisms in fluids drawn in ink See partial translation EL/L1/58 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 3, p 243 B&W negative, red chalk drawing of yeast cells. IM/005319 14 June 1680