Letters written by Leeuwenhoek during Period 1

Alle de Brieven / Collected Letters has over 350 letters. However, only those in this chronology that Leeuwenhoek designated Letter 1, Letter 2, etc. did he consider to contain publishable microscopic observations.

April 28, 1673 Wrote Letter L-001 of 1673-04-28 to Henry Oldenburg about mould and a bee's stinger and eye
August 15, 1673 Wrote Letter L-002 of 1673-08-15 to Henry Oldenburg about the bee, the movement of liquids in wood and food in a louse, and the composition of air
November 8, 1673 Wrote Letter L-003 of 1673-11-08 to Henry Oldenburg about globules in milk and in blood and his theory on the structure and growth of hair and of tumours
April 5, 1674 Wrote Letter L-005 of 1674-04-05 to Constantijn Huygens about globules in milk and blood and the growth of hair; first mention of red blood corpuscles
April 7, 1674 Wrote Letter L-006 of 1674-04-07 to Henry Oldenburg about globules in milk and blood, the growth of hair and nails, and the anatomy of a louse
April 16, 1674 Wrote Letter L-008 of 1674-04-16 to Henry Oldenburg about the delivery of his letters and asking Oldenburg to befriend van Conincxbrugh
April 24, 1674 Wrote Letter L-009 of 1674-04-24 to Constantijn Huygens about his further observations about blood, bones, teeth, and salt
June 1, 1674 Wrote Letter L-011 of 1674-06-01 to Henry Oldenburg about movement of liquid in capillary tubes, structure of body parts, growth of skin, and the size of red blood cells
July 6, 1674 Wrote Letter L-012 of 1674-07-06 to Henry Oldenburg bout sweat, hair, fat, tears, and improved capillary tubes
September 7, 1674 Wrote Letter L-014 of 1674-09-07 to Henry Oldenburg, stating that he will send further observations
September 7, 1674 Wrote Letter L-015 of 1674-09-07 to Henry Oldenburg about the anatomy of the eye and optic nerve of a cow, minerals eg. salt, clay, English and Flemish earth; first mention of protozoa in stagnant water
October 19, 1674 Wrote Letter L-016 of 1674-10-19 to Henry Oldenburg about eggs in the bile of cow, sheep, rabbits and poultry, the structure of metals, skin, and the bladder, and theories about the sense of taste.
December 4, 1674 Wrote Letter L-018 of 1674-12-04 to Henry Oldenburg about optic nerves and sight; enclosed specimen of cow's optic nerve
December 26, 1674 Wrote Letter L-019 of 1674-12-26 to Constantijn Huygens, enclosing a drawing of the optic nerve and excerpts from two recent letters
January 22, 1675 Wrote Letter L-021 of 1675-01-22 to Henry Oldenburg about a new technique for observing blood and sectioned brain tissue; optic nerve, smoke, gunpowder, and scorpions
February 11, 1675 Wrote Letter L-022 of 1675-02-11 to Henry Oldenburg about crystals, vinegar, soap, spices, cod, louse, and oak leaf.
March 26, 1675 Wrote Letter L-024 of 1675-03-26 to Henry Oldenburg about meals, seeds, and pearls; transparency; movement of fluids in plants and animals
August 14, 1675 Wrote Letter L-026 of 1675-08-14 to Henry Oldenburg about blood, taste of saps, sugar, and salt, and the mechanics of taste and digestion
December 20, 1675 Wrote Letter L-028 of 1675-12-20 to Henry Oldenburg about various omissions in previous letters, small animals in water, his theory of “globules”, and the aerometer he devised
January 1, 1676 Wrote Letter L-029 of some time in 1676 to Theodore Craanen about gold and mercury
January 22, 1676 Wrote Letter L-031 of 1676-01-22 to Henry Oldenburg about forwarding his mail and about sending his observations of little animals in water
February 22, 1676 Wrote Letter L-034 of 1676-02-22 to Henry Oldenburg about hair, cow skin, horn, and bone, inviting Hooke's response
April 21, 1676 Wrote Letter L-035 of 1676-04-21 to Henry Oldenburg about movement of liquid in ash and other trees, little animals in wine, and cinnamon and taste
May 29, 1676 Wrote Letter L-037 of 1676-05-29 to Henry Oldenburg about disagreements with Grew about the structure of wood and a further account of the vessels, fibres, and medullary rays of wood
July 28, 1676 Wrote Letter L-038 of 1676-07-28 to Henry Oldenburg; now lost
July 28, 1676 Wrote Letter L-039 of 1676-07-28 to Robert Boyle about the effects of air on ammonia and copper
October 9, 1676 Wrote Letter L-040 of 1676-10-09 to Henry Oldenburg about little animals in various waters and spice infusions, the relationship of their shape to taste, and whether there were little animals in the air
October 30, 1676 Wrote Letter L-043 of 1676-10-30 to Henry Oldenburg about his discussions with Grew and Boyle as well as the unreliability of the postal system
November 7, 1676 Wrote Letter L-045 of 1676-11-07 to Constantijn Huygens summarizing the observations of little animals in Letter L-040
November 27, 1676 Wrote Letter L-047 of 1676-11-27 to Henry Oldenburg, now lost
February 15, 1677 Wrote Letter L-051 of 1677-02-15 to Christiaan Huygens to thank him for translating a letter into French
March 23, 1677 Wrote Letter L-054 of 1677-03-23 to Henry Oldenburg about the quantity of little creatures in one drop of water
May 14, 1677 Wrote Letter L-056 of 1677-05-14 to Henry Oldenburg about muscles, blood, the movement of fluids in fruit, moxa, and cotton
October 5, 1677 Wrote Letter L-058 of 1677-10-05 to Henry Oldenburg about skin, eels, fleas, and measuring and counting the little animals; enclosed testimonials
October 16, 1677 Wrote Letter L-059 of 1677-10-16 to William Brouncker; he is sending some observations and a Latin translation
November 9, 1677 Wrote Letter L-060 of 1677-11-09 to William Brouncker about sperm and their movements in fresh human semen
December 2, 1677 Wrote Letter L-061 of 1677-12-02 to William Brouncker; now lost
January 1, 1678 Wrote Letter L-064 of some time in 1678 to Robert Boyle; now lost
January 14, 1678 Wrote Letter L-067 of 1678-01-14 to Robert Hooke about human blood, blood transfusions, flea larvae, and little animals in pepper water
February 14, 1678 Wrote Letter L-069 to Joseph Williamson, as Grew had requested
March 18, 1678 Wrote Letter L-070 of 1678-03-18 to Nehemiah Grew about sperm in other animals and what Harvey and de Graaf got wrong about reproduction
May 31, 1678 Wrote Letter L-073 of 1678-05-31 to Nehemiah Grew about teeth, bone, hair, and sperm and what de Graaf got wrong about ovulation
September 27, 1678 Wrote Letter L-074 of 1678-09-27 to Nehemiah Grew about sweat and globules in saliva and blood
December 26, 1678 Wrote Letter L-077 of 1678-12-26 to Constantijn Huygens about how son Christiaan's observations of little animals correspond to his own
February 21, 1679 Wrote Letter L-078 of 1679-02-21 to Nehemiah Grew about cod sperm and about not finding any little animals in blood or saliva