BACTERIOLOGY AND PROTOZOOLOGY. 



CHAPTER I. 



INTRODUCTION HISTORY THE PLACE OF 

 MICRCORGANISMS 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 subject 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 characteristics placing them without 

 question among the plants, while others with equal definite- 

 ness belong to the animals. The line between is by no means 

 sharp, and much difference of opinion exists among investi- 

 gators as to the borderline forms. 



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