18 HISTORICAL INTRODUCTION 



also the cause of fermentation. Van Helmont (1578-1644) 

 gives directions for making artificial mice. Kircher (1602- 

 1680) describes and figures animals produced under his own 

 eyes by water on plant stems. 



However, many thinkers of the seventeenth century 

 doubted the truth of this long-established belief. Francesco 

 Redi (1626-1698) made a number of experiments which 

 tended to prove that maggots did not arise spontaneously 

 in meat, as was generally believed, but developed only when 

 flies had an opportunity to deposit their eggs on the meat. 

 It seems that by the latter part of this century the idea 

 that organisms large enough to be seen with the naked eye 

 could originate spontaneously was generally abandoned by 

 learned men. 



The work of Leeuwenhoek served to suspend for a time 

 the subject of spontaneous generation, only to have it revived 

 more vigorously later on. He is usually called "The Father 

 of the Microscope," though the compound microscope was 

 invented probably by Hans Zansz or his son Zacharias, of 

 Holland, about 1590. Leeuwenhoek used a simple lens, but 

 his instruments were so much more powerful that they 

 opened up an entirely new and unknown world. 



Anthony van Leeuwenhoek (1632-1723) was apprenticed 

 to a linen draper, and accumulated a comfortable fortune 

 in this business. He became interested in the grinding of 

 spectacle lenses, then an important industry in Delft, 

 Holland, where he lived, and did a great deal of experimental 

 work in this line, mainly for his own enjoyment. Finally he 

 succeeded in making a lens so powerful that he could see 

 in water and various infusions very minute living bodies 

 never before observed. Leeuwenhoek contributed 112 papers 

 to the Royal Society of Great Britain, the first in 1673, 

 many of them accompanied by such accurate descriptions 

 and drawings, for example a paper submitted September 12, 

 1683, that there is no doubt that he really saw bacteria and 

 was the first to do so (Fig. 1). Rightly may he be styled 

 "The Father of Bacteriology," if not of the microscope. He 

 says in one paper: "With the greatest astonishment I 

 observed that everywhere through the material which I 



