CHAPTER XVII 

 BACTERIA 



Vocabulary 



Sterilized, treated so as to kill all germs, either by heat or chemicals. 

 Culture medium, a substance prepared for growth of bacteria. 

 Peptone, soluble form of proteid. 

 Inoculation, intentional infection with germs. 

 Immunity, a condition in which the body is not affected by bac- 

 terial attack. 

 Indispensable, very necessary. 



Bacteria are very minute, one-celled, parasitic fungous plants. 

 There are many kinds but they are sometimes classified into three 

 groups according to their shape. 



1. Coccus forms round 



2. Bacillus forms oblong 



3. Spirillium spiral and curved 



Do not forget that certain one -celled, parasitic animal forms also 

 cause disease so that when we speak of the germ or microbe, it may 

 mean either a plant or animal parasite, but when bacteria are 

 mentioned, only the plant forms are included. Another point to 

 bear in mind is that not all bacteria are harmful nor are all infec- 

 tious diseases due to bacteria. 



Bacteria are very small, one ten thousandth to one fifty thou- 

 sandth of an inch in diameter. Some are so minute that they can 

 neither be caught by a filter nor seen by a microscope. 



Reproduction. Bacteria, since they have but one cell, absorb 

 food and excrete waste directly. Under favorable conditions of 

 food supply, temperature, and moisture, they reproduce with 

 enormous rapidity, so that one of these microscopic cells would, 

 if unchecked, produce a mass of bacteria weighing 7000 tons in 



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