Letters written by Leeuwenhoek during Period 2

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 25, 1679 Wrote Letter L-080 of 1679-04-25 to Nehemiah Grew about living little animals in fish, hare, and dogs and his calculation that more than ten times as many living animals come from the milt of a cod as there are people living on the Earth
April 27, 1679 Wrote Letter L-081 of 1679-04-27 to Constantijn Huygens about the number of sperm in the milt of the cod
May 11, 1679 Wrote Letter L-083 of 1679-05-11 to Lambert van Velthuysen about people with gout
May 15, 1679 Wrote Letter L-084 of 1679-05-15 to Christiaan Huygens to explain more about his observations of little animals
May 20, 1679 Wrote Letter L-085 of 1679-05-20 to Constantijn Huygens about the number and size of the little animals he was observing
June 13, 1679 Wrote Letter L-087 of 1679-06-13 to Nehemiah Grew asking him to acknowledge two letters from earlier that year
June 13, 1679 Wrote Letter L-088 of 1679-06-13 to Lambert van Velthuysen about the origin of life and the lack of appreciation by physicians and surgeons
July 11, 1679 Wrote Letter L-090 of 1679-07-11 to Lambert van Velthuysen about about the chalk produced by gouty patients and about bladder stones
October 13, 1679 Wrote Letter L-092 of 1679-10-13 to Robert Hooke to inquire of Hooke why he had not received any correspondence from the Royal Society for months, also discussed bladder stones
November 14, 1679 Wrote Letter L-095 of 1679-11-14 to Lambert van Velthuysen about gout, salt, and drinking tea
November 20, 1679 Wrote Letter L-096 of 1679-11-20 to Robert Hooke, copying his Letter L-095 of 14 November 1679 about gout, salt, and drinking tea
January 12, 1680 Wrote Letter L-097 of 1680-01-12 to Robert Hooke about the structure of wood and sperm in fish
January 16, 1680 Wrote Letter L-098 of 1680-01-16 to Robert Hooke, enclosing a copy of Letter L-085 of 1679-05-20 to Constantijn Huygens about the number and size of little animals
February 13, 1680 Wrote Letter L-100 of 1680-02-13 to Robert Hooke that being elected a member of the Royal Society would be an honour
April 5, 1680 Wrote Letter L-102 of 1680-04-05 to Robert Hooke about the testicles and sperm of a rat and organisms in the gills of oysters and in the sap of vines
May 13, 1680 Wrote Letter L-104 of 1680-05-13 to Members of the Royal Society expressing his surprise and gratitude at being elected a member
May 13, 1680 Wrote Letter L-105 of 1680-05-13 to Robert Hooke to gratefully accept his election as a foreign member of the Royal Society and to acknowledge the receipt of his diploma
May 13, 1680 Wrote Letter L-106 of 1680-05-13 to Thomas Gale about little animals in sap and whether little animals are in the air
June 14, 1680 Wrote Letter L-107 of 1680-06-14 to Robert Hooke, a short cover letter
June 14, 1680 Wrote Letter L-108 of 1680-06-14 to Thomas Gale about beer, yeast, crab's eyes in vinegar, and little animals reproducing in hermetically-sealed tubes
August 9, 1680 Wrote Letter L-109 of 1680-08-09 to Robert Hooke to ask whether the Royal Society received previous letters and to promise further investigations into the formation of blood
September 28, 1680 Wrote Letter L-110 of 1680-09-28 to Thomas Gale to inquire whether Letter 107 of 1680-06-14 had arrived
November 12, 1680 Wrote Letter L-111 of 1680-11-12 to Robert Hooke about blood globules, lees of wine, globules in rain water, milk vessels, reproduction, little animals in the male seed of animals, and their incomprehensible smallness
November 4, 1681 Wrote Letter L-114 of 1681-11-04 to Robert Hooke about hog bristles, shedding hair, blackheads; living little animals in excrement, horse urine, clay, and gout
March 3, 1682 Wrote Letter L-116 of 1682-03-03 to Robert Hooke about muscle fibres, hair, the cell nucleus in the erythrocytes of fishes, the liver of salmons, beards of oysters, and the structure and growth of oyster shell
April 4, 1682 Wrote Letter L-119 of 1682-04-04 to Robert Hooke about the structure of the muscle tissue of lobsters and shrimps.
July 28, 1682 Wrote Letter L-120 of 1682-07-28 to Robert Hooke, now lost, asking whether figures of the anatomy of wood in Letter L-097 of 12 January 1680 will be published in print
January 22, 1683 Wrote Letter L-122 of 1683-01-22 to Christopher Wren about the function of the ovary, muscles of insects, drinking tea and mild beer, erythrocytes, and a theory on the formation of blood
March 9, 1683 Wrote Letter L-124 of 1683-03-09 to Francis Aston promising to send observations about generation and colors
May 20, 1683 Wrote Letter L-126 of 1683-05-20 to Anthonie Heinsius about generation and about the circulation of the blood, which he intends to communicate in a letter to the Royal Society
July 16, 1683 Wrote Letter L-128 of 1683-07-16 to Christopher Wren about the procreation of frogs, sperm in fowl's egg, reproduction of rabbits, little animals in frog intestines, a theory about digestion in humans and fish, and blood
July 22, 1683 Wrote Letter L-129 of 1683-07-22 to Anthonie Heinsius about Heinsius's reactions to an earlier letter
September 2, 1683 Wrote Letter L-132 of 1683-09-02 to Anthonie Heinsius, requesting his opinion of observations in Letter L-128
September 16, 1683 Wrote Letter L-134 of 1683-09-16 to Anthonie Heinsius about whether Heinsius would like a copy of his speculations on the living organisms in mouths and on the structure of the skin
September 17, 1683 Wrote Letter L-135 of 1683-09-17 to Francis Aston about saliva, nasal hairs and blackheads, skin, pores, calluses, and cleaning teeth; the discovery of bacteria in tartar
September 30, 1683 Wrote Letter L-136 of 1683-09-30 to Anthonie Heinsius, a note accompanying a copy of Letter L-135
October 14, 1683 Wrote Letter L-141 of 1683-10-14 to Anthonie Heinsius in reply to his recent Letter L-139
December 28, 1683 Wrote Letter L-144 of 1683-12-28 to Francis Aston about human skin and its diseases, the intestines, the effects of vinegar, the intestinal wall and peristalsis, and an experiment to demonstrate the adsorption of food nutrients in the intestines.
April 14, 1684 Wrote Letter L-147 of 1684-04-14 to Francis Aston about lenses and corneas, the function of eye-lids, the involuntariness of blinking, the optic nerve, and the skin of Moors
July 25, 1684 Wrote Letter L-150 of 1684-07-25 to Members of the Royal Society about parts of the brain of several animals, chalk stones of gout, leprosy, and the scales of eels
January 5, 1685 Wrote Letter L-152 of 1685-01-05 to Members of the Royal Society about salts in wine and vinegar and in the stomach, the eye, the need for food and water, Descartes's theory on smallest water particles, and a theory of taste - salt, sour and sweet
January 23, 1685 Wrote Letter L-154 of 1685-01-23 to Members of the Royal Society about salts and their crystals and his theory about the causes of taste
March 30, 1685 Wrote Letter L-157 of 1685-03-30 to Members of the Royal Society about sperm, the uterus of a bitch, sheep embryos, ovaries in young animals and apples, and his claims that sperm are the life-carriers and that there are male and female sperm
July 13, 1685 Wrote Letter L-159 of 1685-07-13 to members of the Royal Society about reproduction of trees, transfer of nutrients, male and female trees, hazelnut, comparing reproduction of mammals with reproduction of plants, cross-breeding, and germination
August 10, 1685 Wrote Letter L-162 of 1685-08-10 to Anthonie Heinsius about cochineal
September 21, 1685 Wrote Letter L-164 of 1685-09-21 to Anthonie Heinsius about cochineal
October 12, 1685 Wrote Letter L-166 of 1685-10-12 to members of the Royal Society about the beginning of plants in seeds; chyle, sweat, about skin, optic nerve, and bile of fish; salts in beer vinegar and lemon juice; and spirits mixed with blood and wine vinegar
January 22, 1686 Wrote Letter L-168 of 1686-01-22 to members of the Royal Society about cinnabar naturalis, gunpowder, saltpeter, and air made by gunpowder and crab's eyes
April 2, 1686 Wrote Letter L-173 of 1686-04-02 to members of the Royal Society about the structure of bone, the bark of trees, skin and scales, the moisture evaporating from his body, and a little peeling piece of skin
April 14, 1686 Wrote letter L-174 of 1686-04-14 to Antonio Magliabechi, now lost
May 14, 1686 Wrote Letter L-175 of 1686-05-14 to members of the Royal Society about gall-nuts found on oak trees and the germination of plants
June 10, 1686 Wrote Letter L-177 of 1686-06-10 to members of the Royal Society about seeds of cotton, kapok, Bupariti, and coconuts, the reproduction of shrimp and lobster, and the eggs of shell fish
July 10, 1686 Wrote Letter L-178 of 1686-07-10 to members of the Royal Society about the growth and durability of wood felled in different seasons and countries, the annual growth rings, and how wooden barrels can be made watertight
September 10, 1686 Wrote Letter L-180 of 1686-09-10 to Daniël Papenbroek, a cover letter for Letter L-181
October 30, 1686 Wrote Letter L-182 of 1686-10-30 to Antonio Magliabechi, a cover letter for copies of two of his books