INTRODUCTION. 19 



In the year 1683 he discovered in the tartar scraped 

 from between the teeth a form of micro-organism upon 

 which he laid special stress. This observation he em- 

 bodied in the form of a contribution to the Royal Society 

 of London on September 14, 1683. This paper is of 

 peculiar importance, not only because of the careful, 

 objective nature of the description given of the bodies 

 seen by him, but also for the illustrations which accom- 

 pany it. From a perusal of the text and an inspection 

 of the plates there remains little room for doubt that 

 Leeuwenhoek saw with his primitive lens the bodies now 

 recognized as bacteria. 1 



Upon seeing these bodies he was apparently very 

 much impressed, for he writes : " With the greatest 

 astonishment I observed that everywhere throughout 

 the material which I was examining were distributed 

 animalcules of the most microscopic dimensions, which 

 moved themselves about in a remarkably energetic way." 



This discovery was shortly followed by others of an 

 equally important nature. His field of observation 

 appears to have increased rapidly, for after a time he 

 speaks of bodies of much smaller dimensions than those 

 at first described by him. 



Throughout all of Leeuwenhoek's work there is a 

 conspicuous absence of the speculative. His contri- 

 butions are remarkable for their purely objective 

 nature. 



After the presence of these organisms in water, in 

 the mouth, and in the intestinal evacuations was made 

 known to the world, it is not surprising that they 

 were immediately seized upon as the explanation of the 



1 See Arcana Naturae detecta ab ANTONIO VAN LEEUWENHOEK ; 

 Delphis Batavorum, 1695. 



