Drawings of animalcules from Leeuwenhoek's letter, 17th September 1683 to the Royal Society in London, in which he describes what he saw when he mixed white matter" from between his cleaned teeth with rain water & examined it under his microscopes. The animalcules are now identified as types of bacteria. A) is a motile bacillus. B) Selenomonas buccalis & the track of its movement (C to D). E) Micrococci. F) Leptothrix buccalis. G) A spirochaete, probably Spirochaeta buccalis, the largest one occuring in the mouth. Figure F does not appear in the original letter. It was published in a Latin edition of Leeuwenhoek's work titled Arcana Naturae Detecta (1695)."