Structure of the letters in Period 2

The 25 letters that Leeuwenhoek numbered and self-published from 1679 to 1687 (Period 2) have similar structure. On the right (click to enlarge) is the first page of the printed version of Letter 43 of January 5, 1685 (AB 82) to Members of the Royal Society. It was, as were all of Leeuwenhoek's self-published letters, preceded by a summary that was not in the manuscript and thus not in any of the volumes of Alle de Brieven / Collected Letters.

The 29 unnumbered letters share some of these structural features.

All 54 letters had openings and closings of the conventional formal nature common to the Seventeenth Century. They were not usually printed with the extract in Philosophical Transactions, but Leeuwenhoek always included them in his self-published volumes. For example, the letter of October 30, 1686, to Antonio Magliabechi began:

Most Illustrious, Highly Learned and Very Renowned Sir

The letter of May 13, 1680, to the members of the Royal Society ended:

Praying that the Almighty may mercifully protect you each and all, I am, Gentlemen,

Your most obedient servant,

The body of every letter referred to, described, and discussed the specimens that Leeuwenhoek observed, many illustrated with figures. In the process, he sometimes noted the source of his specimens and the methods he used to study them.

Before, after, and in between his observations, Leeuwenhoek wove a number of other topics that fall into four types, shown in the box on the right. An individual letter may or may not address them, so the table below shows which letters included information of each type.

Repeated topics in Leeuwenhoek's letters

His response to other researchers, usually by name and the publication to which Leeuwenhoek was responding.

The reception of his discoveries by the public and their opinions on things that his observations confirmed or, usually, debunked.

Arithmetic calculations that he made of the size and number of the microbes that he observed.

The visitors to his house, usually by name.

The columns on Leeuwenhoek's response to other researchers and their books and to the public make it clear. Far from being a solitary genius, Leeuwenhoek was part of a network of other scholars and interested members of the public, some of whom visited his house and only some of whom he mentioned in his letters. Along with dozens of other researchers who used empirical methods and exchanged information in the form of letters, Leeuwenhoek was a participant in what even then was called the Republic of Letters. Their research responded to his and his research responded to theirs.

Leeuwenhoek was also concerned with how his observations contradicted or confirmed what most people thought. The column on calculations shows Leeuwenhoek's awareness of the difficulty people had accepting the minute sizes and innumerable quantities he reported in his letters.

Key to the table

The letters themselves had no headings or subheadings; the column headings on the table below did not appear in the letters themselves. Nor did the contents of the table cells unless enclosed in quotation marks. The quotations give a sense of the text. A blank cell indicates that the letter did not address that topic.

For more on each letter's content, see the page for that letter below under Learn more or the pull-down menu at the top of the right sidebar.

 Letter Response to other researchers Public reception Calculations Visitors to his house
28
1679-04-25
  "Fire in the little animals." How many little animals?  
29
1670-01-12
Robert Hooke

members of the Royal Society

  How much water circulates in a tree?  
30
1680-04-05
  "It appears impossible even to myself."    
31
1680-05-13
       
32
1680-06-14
Francesco Redi    
33
1680-11-12
  "I only tell fictitious stories about the little animals." How small are the little animals?  
34
1681-11-04
       
35
1682-03-03
Stephen Blankaart   How small are muscle fibers?  
36
1682-04-04
Robert Hooke      
37
1683-01-22
Regnier de Graaf

unnamed physician

Heydentryck Overkamp

"Why are there so many thousands of little animals in one drop?"    
38
1683-07-16
Dionisius van der Sterre

Cornelis Bontekoe

"I shall be contradicted by many all over the world."    
39
1683-09-17
members of the Royal Society "They vowed they would never use vinegar again."    
40
1683-12-28
some physicians

Stephen Blankaart

"I examined the child closely which did not please the showmen."    
41
1684-04-14
  "I coated the ball - thus wound about - with strong glue." How many fibers in the lens of an eye? interested gentlemen
42
1684-07-25
Dr. Willem ten Rhijne

Herman Bushoff

  How small are blood vessels in the brain?

How small are blood vessels in the human eye?

 
43
1685-01-05
Heydentryck Overkamp

Rene Descartes

"Speculations ... are nothing but brain-work." How large is a particle of salt?  
44
1685-01-23
  "A given remedy does not have precisely the same effect upon all cases of the same disease."    
45
1685-03-30
Charles Drelincourt

Johannes van Dueren

"Here, then, we have another of the most absurd fallacies relating to the theory of sucked-off eggs."   Charles Drelincourt

Cornelis 's Gravesande

Cornelis Bontekoe

other “learned gentlemen, including four doctors of medicine”

46
1685-07-13
       
47
1685-10-12
Nehemiah Grew "Many persons cannot accept what I write, and boldly dare to say that they do not believe me."   A former captain in the East Indies
48
1686-01-22
       
49
1685-04-02
Thomas Gale "I am well aware that many persons believe ...." How many sweat vessels in skin?  
50
1686-05-14
Jean Baptiste Tavernier "He had dismissed one of his maids, because she was full of lice."

"The miraculous power to cure of haemorrhoids or piles was to me incredible."

   
51
1686-06-10
Paulus Hermans "Those who still, through prejudice, embrace the stupid and fanciful propositions." How small is a crab's egg? Mr. Colson
52
1686-07-10
  "The ability to learn from their mistakes."