BACTERIOLOGY AND PROTOZOOLOGY 



CHAPTER I 



INTRODUCTION HISTORY THE PLACE OF 

 MICROORGANISMS IN NATURE 



INTRODUCTION 



THE study of disease has brought to light many 

 facts which demonstrate the effect of the association 

 of different forms of life. Chief among these is the 

 fact that minute beings live upon greater ones, either 

 harmlessly or to the detriment of the latter. The study 

 of these small creatures is called microbiology, this 

 being the portion of general biology in which the use 

 of magnification is necessary. Bacteria are classified 

 as plants and their study is called bacteriology. The 

 smallest animals, protozoa, are considered in the sub- 

 ject of protozoology. To explain the causation of 

 infectious diseases the physician has been obliged to 

 study both of these subjects, that is, the large field of 

 microbiology. The lowest forms of life are unicellular 

 bodies capable of leading an independent existence, in 

 contrast to the single units of the cell groups which go 

 to make up the compound organism, a higher animal 

 or a plant. Some of these single-celled bodies have 

 2 



