CHAPTER II 



CONDITIONS FOR GROWTH AND PRODUCTS OF THE 

 GROWTH OF BACTERIA 



Soil. Bacteria differ in their selection of material 

 upon which they grow: some preferring dead organic 

 matter, others living only on the tissues of living or- 

 ganisms. Some grow well on either soil. 



Saprophytes are those bacteria which grow on dead 

 organic matter; for this reason they must be looked upon 

 as benefactors to the human race. It is through their 

 action that dead bodies and other highly complex or- 

 ganic materials are broken up into simpler forms and 

 reduced to the dust from whence they sprang; thus is 

 the earth rid of its carrion, and at the same time vegeta- 

 tion, upon which man and the higher animals subsist, is 

 furnished with the simpler compounds of nitrogen, 

 hydrogen, carbon dioxid, ammonia, and water necessary 

 for its growth. 



Parasitic bacteria live upon living tissue of man and 

 other animals, and must, therefore, be looked upon as 

 foes of mankind. 



Pathogenic bacteria are those bacteria which produce 

 disease. Inasmuch as practically all parasitic bacteria 



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