BACTERIOLOGY IN A NUTSHELL. 



Parasitic 

 Bacteria 

 Our Foes. 



Good 

 Bacteria. 



more numerous than the parasites. Of the num- 

 berless species of bacteria only about forty (40) 

 are known to cause disease in man. Parasites 

 are enemies to animal life; they are the so- 

 called disease germs" or "microbes"; they 

 exist only at the expense of other living bodies. 

 They invade various parts of the living body 

 and under favorable conditions they weaken 

 and sometimes destroy the parts they invade. 

 They take away from us substances on which 

 our health is dependent, and deposit in their 

 place that which poisons and frequently com- 

 pletely destroys. Because of their power to 

 produce pathological changes in animal bodies, 

 parasitic bacteria are also called pathogenic 

 bacteria. 



Saprophytic bacteria not only are our friends, 

 but they are of such benefit to mankind that we 

 could not live without them. They live upon 

 dead organic matter, and by their activities de-- 

 composition, fermentation and putrefaction are 

 produced. Nourishment necessary to the sus- 

 tenance of vegetable life is derived from car- 

 bonic acid gas, ammonia and water, which are 

 all produced by the action of saprophytic 

 bacteria on dead animals and vegetables. Veg- 

 etable and plant life would cease to exist if the 

 carbon and nitrogen to which they owe their 

 growth and development could not be obtained 

 from this source. Animal life is sustained, by 

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