Letter, from Antoni van Leeuwenhoek to Francis Aston, dated at Delft Signed autograph Further observations of saliva, Leeuwenhoek's method for cleaning his teeth and the discovery of bacteria in tartar; examination of spittle from people of different ages and sex; observations of nasal hairs and blackheads (comedones); concerning the structure of the epidermis and comparing scabs with fish scales; discussion of pores and calluses Original figures 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 119 English extract printed in 'Philosophical Transactions', vol 14, no 159, p 568 English extract printed in 'Philosophical Transactions', vol 17, no 197, p 646 B&W negative, text only, Box N101. IM/005322 17 September 1683