Chapter II 



BACTERIOLOGY 



Origin Several of the philosophers of an- 

 tiquity surmised the existence of living organ- 

 isms too small to be seen by the unaided human 

 eye. However, prior to the work of the Dutch 

 microscopist Leeuwenhoek, in the latter part of 

 the seventeenth century, definite ocular evi- 

 dence for the belief on this point did not exist. 

 Leeuwenhoek (1632-1723) spent many years ex- 

 amining through the microscope a great variety 

 of natural objects and, in the course of his ob- 

 servations, chanced to come across the micro- 

 organisms now known as bacteria. He supple- 

 mented his observations with drawings, and 

 there is no doubt that he was the first to see 

 bacteria and describe them accurately. Al- 

 though Leeuwenhoek himself made no medical 

 application of his discoveries, others did so ; and 

 the " animalcule" or "germ" theory of disease 

 was promulgated to explain the causation of 

 many morbid conditions then ill understood. 



Leeuwenhoek 's observations remained prac- 



21 



