Preface
Only slightly later than the planned time after the appearance of Volume 7 of ‘The Collected Letters of Antoni van Leeuwenhoek’, Volume 8 is presented to the reader. It contains the letters 110 up to 119 inclusive, written between 7 September, 1688 and 7 March, 1962 inclusive, thus covering a period of just three and a half years. Out of the ten letters included, seven were numbered by Leeuwenhoek himself: his numbers 65 up to 71 inclusive. The others are so-called intermediate letters, which were sent by Leeuwenhoek, without numeration, to several scholars of his time. Among these it is in particular the letter to Magliabechi of 18 September, 1691, our no. 115, which deserves attention. A variety of subjects are touched upon, and a fairly large number of contemporaries of Leeuwenhoek are mentioned.
Letter 110 (65) is widely known. It is the repeatedly published letter on Leeuwenhoek's observations about the circulation of the blood. In fact, already at that time the passage of the arterial blood to the venous system via the capillaries did not escape his notice. His object of observation was the larva of the frog, and as ‘is his custom’, he did not fail to observe and describe accurately the stages in the development from the egg to the tadpole and to the frog.
Letter 113 (66) essentially deals with the same subject, the circulation of the blood, but this time in various other animals. The so-called eelspy-glass is described at length in this letter, and of course the circulation of the blood in the tail of an eel forms a special subject of study, although he had already devoted attention to it in preceding letters.
Letter 114 (67) deals with the mechanical and hydrostatic problems involved in the circulation of the blood. Leeuwenhoek here also devotes much attention to the circulation of the blood of higher animals, in particular that of the bat.
Letter 119 (71) is devoted to the life cycle of the corn-moth; on the basis of the fundamental investigation not only does he devise a system for combating this noxious incset, but he also describes an experiment performed with it.
So far about the (broad) contents of the letters of Volume 8. Of all the Leeuwenhoek-numbers included, the manuscript again was present in the archives of the Royal Society in London, so that these original documents without exception formed the basis for the preparation. As usual, Dr. B.C. Damsteegt untiringly saw to the Dutch linguistic preparation of the next. Mr. E. van Loo again translated it into Englisch. The Commission cannot be grateful enough for their willingness to continue to lay these essential foundations of protracted preparation of ‘The Collected Letters’. The unity of the work is considerably promoted by it. We owe no less a debt of gratitude to