Letter, from Antoni van Leeuwenhoek to Henry Oldenburg, dated at Delft Signed autograph Observations about the structure and nature of blood, and the growth of skin and of plants Further theories about the motion of liquid in tubes and the globular form of fluid bodies The microscopical observations of the structure of bone, teeth, liver, and brain Technique for examining the cerebral texture, spinal marrow and muscular tissue Concerning the growth of the epidermis Figures of capillary tubes in margin. A small envelope containing three original small packets was attached to the last sheet and is now stored separately. The packets contained specimens: of cork; of pith of elder; and the white of a quill. The original packets contain >70% of the original material, in 1981 Brian Ford separated two portions of the samples, a first portion was placed in separate packets, kept in an envelope; a second portion of the samples were sputtered in gold and are kept in a separate container. For summary see 'The correspondence of Henry Oldenburg', ed and trans by A Rupert Hall & Marie Boas Hall, vol 11, p 23 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, part 1, p 90 See 'The van Leeuwenhoek specimens' by Brian Ford in 'Notes and Records', vol 36, no 1, pp 37-59 at p 46 for further information 1 June 1674