294 ORGANIC EVOLUTION CONSIDERED 



himself. Many things that were formerly regarded as 

 worthless, have, in recent times, been made to minis- 

 ter to his welfare. 



Many organisms that would seem to be useless 

 serve to advance the general good of the organic 

 world. Numerous humble forms, such as worms and 

 insects, loosen the soil, thus adapting it the better for 

 the growth of plants, while all organic beings by 

 the decomposition of their bodies render the soil 

 more fertile. In fact, the fertility of soils depends 

 largely upon the decomposition of organic remains. 

 Many organisms act as scavengers, thus helping to 

 purify the earth and to render it a more fit dwelling- 

 place for man. 



The relations between minerals, plants and ani- 

 mals show a wise economy in the use of materials. 

 Minerals serve as food for plants, and plants as food 

 for animals; and when these organisms decay they 

 give back to the air and the soil the materials of 

 which they are composed, mostly in such inorganic 

 forms as serve for the food of plants. In this way 

 the same matter may enter in succession into count- 

 less organic beings. 



Plants purify the air for animals by removing from 

 it carbon dioxide, and animals exhale this gas for the 

 use of plants. During the Carboniferous Age, the 

 amount of carbon dioxide which plants removed from 

 the air was enormous, as is shown by the great depos- 

 its of coal in many parts of the world, and in this 

 way the air was the better adapted to the use of the 

 higher animals, and coal was stored up in anticipa- 

 tion of the coming man. 



Organic matter has also, by its deoxidizing power, 

 played an important part in storing up in many places 

 beds of iron ore for the use of man. 



The wonderful adaptations of many flowers and in- 



