BACTERIOLOGY. 
DEFINITION, OCCURRENCE, STRUCTURE, PRODUCTS 
AND DEVELOPMENT OF BACTERIA. 
What are bacteria ? 
They are minute vegetable organisms of the simplest form. They 
are microscopic in size and contain no chlorophy! as do plants of higher 
types. 
Where are they found ? 
In the air, water and surface soil. They are especially abundant 
about human habitations, or wherever there is decaying organic 
matter. 
To what is putrefaction due ? 
To the presence and activity of bacteria. 
What effect do bacteria have upon dead organic matter ? 
They separate the complex structures of animal and vegetable life 
into simpler compounds. A small part of the resulting elements they 
use as food while the greater part is set free. It is by the activity of 
these ininute organisms that suitable food is prepared for more highly 
organized plants, which in turn go to support animal life. It can 
therefore be said that without the bacteria all life would ultimately 
cease. 
What are saprophytes ? 
Saprophytes or saprophytic bacteria are the ones which grow upon 
dead organic matter and cause decomposition and fermentation. 
What are parasites ? 
Parasites or parasitic bacteria require as their place of growth a 
living organism. They not only appropriate for their own nourish- 
ment material necessary to the well-being of the organism in which 
they are growing, but also form products which are poisonous to the 
surrounding tissues. Pathogenic or disease-producing bacteria belong - 
to this class. 
Are bacteria normally present in the human body ? 
Yes; especially in the alimentary tract, where they perform the 
offices of saprophytic bacteria. 
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