SECTION I. 



GENERAL BACTERIOLOGY. 



INTRODUCTION THE DEVELOPMENT AND SCOPE OF 

 BACTERIOLOGY. 



BACTERIOLOGY is that branch of Natural Science which treats of 

 the structure, functions and chemistry of bacteria. Bacteria are 

 intimately related to many fields of human activity, therefore bacterio- 

 logy is inseparably associated with a number of the arts and sciences. 

 In those branches of science which treat of the diseases of plants, 

 of animals and of man, bacteria enter into complex reciprocal relations 

 with their hosts as parasites or pathogens, relations which are neither 

 purely bacterial, animal nor vegetal in their limitation. A new science, 

 Immunology, is rapidly developing which is concerned chiefly with 

 the elucidation of these relationships between host and parasite. 



Bacteria are the smallest in size and simplest in structure of known 

 visible living organisms. They are rigid unicellular organisms devoid 

 of chlorophyll or other photodynamic pigment; they possess no 

 morphologically demonstrable nucleus and reproduce by simple 

 transverse fission, the resulting individuals being of approximately 

 equal size. 



Bacteria are ubiquitous in their distribution; they are found in all 

 climates in association with animal and vegetable life. Some thrive 

 at temperatures but slightly above the freezing point of water; the 

 majority flourish between 15 and 40 Centigrade; some even develop 

 in thermal springs at a temperature of 70 Centigrade. Free or atmos- 

 pheric oxygen is essential for most types of bacteria, but to a few it 

 is actually a poison. 



Bacteria are ordinarily classed as plants, but they exhibit several 

 prominent characteristics which suggest a relationship with the lowest 

 animals. The most important of these is the absence of photodynamic 

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