APPLIED BAOTEEIOLOGY. 



CHAPTEE I. 



INTRODUCTION. 



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

 genesis theories — Structure of micro-organisms — Types and size of 

 organisms — Method of reproduction — Bate of growth — Movements 

 of bacteria — Classification of micro-organisms — Conditions and 

 products of growth — Besistance of bacteria to physical influences : 

 Kght, heat, etc. — Sterilisation — The antagonism of micro-organisms. 



Fae 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 

 tagji 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 algae. 



Bacteria are distributed everywhere in Nature ; they 

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

 in greater or lesser numbers in air, water, dust, etc. We 

 only perceive their presence under ordinary circumstances, 

 however, when the conditions are favourable to their 

 growth and development. Sometimes they give rise to a 

 putrefactive smell, or impart a colour to the body on which 



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