APPLIED BAOTEEIOLOGY. 



CHAPTEE I. 



INTRODUCTION. 



Bacteria : their history and place in Nature — The abiogenesis and 

 biogenesis theories — Structnre of micro-organisms — Types and size 

 of organisms — Method of reproduction — Bate of growth— Move- 

 ments of bacteria — Classification of micro-organisms — Conditions 

 and products of growth — ^Variation of bacteria — Eesistance of 

 bacteria to physical influences : light, heat, etc. — Sterilisation — 

 Action of cold, desiccation, electricity, chemical agents. 



Far down in the scale of life is a large group of organisms 

 which are spoken of in a general way as micro-organisms, 

 bacteria, microbes, germs, etc. The bacteria are so small 

 and simple in their structure, that it has been no easy 

 task for the biologist to decide whether they belong to 

 the animal or vegetable kingdom. It is now definitely 

 settled, however, that they are plants, and are closely re- 

 lated to the algse. The continued hfe of the vegetable and 

 the animal kingdoms is due to their activity, and is 

 modified by it. The science of bacteriology investigates 

 their life-history and its results. 



Bacteria are distributed everywhere in Nature ; they 

 cling to the surface of every substance, and are to be found 



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