20 The Story of the Bacteria 



to the needed conditions and the spore swells 

 into a bacterium again, and the roots of 

 a new ancestral tree begin to sprout. 



These bacteria are really very simple forms 

 of cells, and like the cells 

 which we have looked at in 

 the last chapter, their life 

 expresses itself in certain 

 activities; they move, they 

 nourish themselves and 

 grow, they reproduce their 

 kind. They have the power in carrying on 

 the processes of their own nutrition, when 

 moisture and air are present, of tearing to 

 pieces, in the chemical sense, dead organic 

 material, using up such parts of it as they need 

 for their own purposes, and setting free the 

 rest in such form as to be available for the use 

 of other living things. 



Everybody knows who thinks about it, that 

 the supply of such material as makes up the 

 bulk of the tissues of man, animals, and plants, 

 on this earth, is limited. So that if things were 

 not so arranged that living beings should have 

 the use of the material which goes to make up 



