Preface
Through a variety of circumstances the publication of Volume IX of The Collected Letters of Antoni van Leeuwenhoek has been delayed much longer than the Commission cared for. The principal causes consisted on the one hand in the tardy way in which requested notes were forthcoming and on the other hand in changes in the staff of workers on this edition, to be mentioned below. However, the Commission and the present editor seriously intend to speed up the publication of the later volumes.
Volume IX contains the Letters 120 up to and including 133, written between 22 April 1692 and 24 February 1694, i.e. a period of nearly two years. Eight of these letters were numbered by Leeuwenhoek himself: 72 up to and including 79. The other six letters are the so-called intermediate letters, which he sent, without numbering them, to Richard Waller, Queen Mary II of Great Britain, and Pieter Rabus.
As has been done previously, in this volume again some letters have been included which were written to Leeuwenhoek by contemporaries, viz. by Christiaan Huygens, Richard Waller, George Garden, and Pieter Rabus, since they elucidate the content of Leeuwenhoek's letters to some extent.
The Letters 120 [72] and 121 [73] describe a number of experiments with an air-pump, from which Leeuwenhoek draws the conclusion that blood does not play any appreciable role in the absorption of air into the body.
In Letter 122 [74], which deals with the anatomy of wood, he reconsiders his earlier views about the structure and function of various elements of wood.
In Letter 123 [75] Leeuwenhoek again describes his observations of micro-organisms in dental tartar and makes an - unsuccessful - attempt to elucidate the reproduction of the eel.
In Letter 126 [76] a wonderful description of the reproduction of the flea is to be found.
Letter 129 [77] contains excellent observations on the reproduction of the mite and the louse.
In Letter 131 [78] Leeuwenhoek deals with some worms which are parasitic on man and makes an attempt to build up a theory about the way in which the infection takes place.
In Letter 133 [79], finally, Leeuwenhoek evinces his interest in chemistry and describes the oxidation of white phosphorus.
The notes contain more details than in earlier volumes about the notions of Leeuwenhoek's contemporaries, which throw into relief the background of his observations and views. Additional remarks will also be found, which are based on the records of the Royal Society and concern the receipt and the handling of the letters to this learned society. Furthermore, a separation has been brought about between the alternative readings of the text and the scientific notes.
The preparation of some of these letters was still attended to by Dr J.J. Swart, to whom the Commission is indebted for the editing of the three preceding volumes. Dr Swart laid down his task on 1 January 1969; it was taken over by Drs J. Heniger, who is on the staff of the Biohistorical Institute at Utrecht, where the editorial activities already took place from the moment the former editor took up his task.