156 LIFE ON THE FARM 



strength, but has added thereto. Here is where 

 these wonderful micro-organisms perform such an 

 important part in the physical and chemical 

 changes going on in the earth's crust. 



As soon as plants and animals die, decomposi- 

 tion sets in due to the action of bacteria. When 

 their bodies fully decay, as much substance is 

 returned to the earth as was taken from it by them. 

 Another generation of plants and animals uses up 

 this; but they, in turn, give back their bodies in 

 decay to the soil. Thus, in nature's cycle of 

 change, there is a using over and over again of the 

 same substances; but the powerful action of bac- 

 teria makes it possible for the complete transfor- 

 mations to take place. 



Even if the soil had been extremely fertile and 

 deep in the beginning, the bodies of dead plants 

 and animals would have accumulated to such an 

 extent as to make further life impossible, had it 

 not been for the presence of decomposing germs. 

 Bodies of animals have been found preserved for 

 ages in the ice of very cold regions. Decomposi- 

 tion did not take place because bacteria are dor- 

 mant at such low temperatures. 



It is similar with dried specimens. Decomposi- 

 tion germs cannot work without the presence of 

 moisture. So bacteria keep the surface of the 

 earth free from dead bodies of plants and animals 

 by decomposing them and returning them to the 

 soil from whence they came. Bacteria are thus 



