MICROBIOLOGY 



naturalist and pioneer in the world of the infinitely little. 

 By the aid of home-made lenses of wonderful efficiency, he 

 found in the saliva from the human mouth minute organ- 

 isms to which he gave the name animalcula on account of 

 their power of movement. 



Pig. 1. Oldest known figures of genuine bacteria (Bacteria of 

 the mouth) from v. Leeuwenhoek. A and F represent Bacillus 

 buccalis maximus. B is perhaps Vibrio buccalis; its movements were 

 followed by v. Leeuwenhoek from C to D. E is a species of coccus 

 and G no doubt Spirillum sputigenum (Fischer). 



In the description x and in the figures he gives curved 

 and straight forms; long and short rods are plainly recog- 

 nizable. They constitute the first reliable record of bacteria, 

 the study of which in later times has revolutionized medi- 

 cine and expanded into a new science. 



After van Leeuwenhoek, the study of these lower forms 

 was given up, because of the difficulty of observing them 

 with the simple microscope. The discovery of the com- 

 pound microscope marked a great advance in the study of 

 microorganisms. Miiller 2 was the first to apply this dis- 



1 van Leeuwenhoek. Arcana naturae detecta. The figure dates 

 from the year 1683, and is taken from a new edition of the Arcana 

 published in 1722 (vol. ii, p. 40). 



2 Miiller. Vermium terrestrium et fluviatilium Historia, 1774, 

 and Animalcula infusoria fluviatilia et marina, 1786. 



