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 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 mor- 
phologically demonstrable nucleus and reproduce by simple transverse 
fission, the resulting individuals being of approximately equal size. 
This monotony of form characteristic of bacteria, combined with a 
considerable versatility of physiological activity, has compelled the bac- 
teriologist to pay much attention to means w^hereby such activities 
may be registered accurately in order that they may serve as a supple- 
mentary basis for classification. These manifestations of cell activity 
furthermore have become most important phenomena for study, since 
it is through such considerations that the elucidation of the phenomena 
of parasitism and pathogenesis, of infection and immunity must be 
sought for. 
"It is what bacteria do, rather than what they are," as Theobald 
Smith has so aptly said, "since our interest centers in the host rather 
than the parasite." What bacteria do is a problem in dynamics— of 
chemistry and physics— rather than one of pure morphology, and in 
this sense bacteriology is a focal point of the natural sciences. 
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° C. ; some even develop in thermal 
springs at a temperature of 70° C. Free or atmospheric oxygen is 
essential for the development of most types of bacteria, but to a few it 
is actually a poison. 
Bacteria are intimately related to many fields of human activity, 
therefore bacteriology 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 
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