THE BEGINNINGS OF LIFE. 133 



plants only^ and merely transferred by digestion to the bodies 

 of etwmals? 



Thus we find that the vegetable world is the great 

 originator and source of that pabulum which is necessary 

 for the existence of animals. Plants are the active 

 agents ever ministering to the wants of animals. They, 

 in fashioning their own structures, are continually 

 giving birth to organic substances which are to consti- 

 tute the materials necessary for the maintenance of 

 animal life. Animals, as a rule, are powerless for the 

 creation of organic matter 1 j they can assimilate and 

 modify the organic substances which have been built 

 up for them in the tissues of plants ; but they cannot 

 abstract from earth, air, and water the elementary con- 

 stituents of organic matter, and force them to enter 

 into such and such combinations. They use the 

 materials which have been elaborated for them by 

 plants, since they all feed either directly upon members 

 of the vegetable kingdom, or else indirectly by living 

 upon animals which have been so nourished. Plants, then, 

 are the great factors of organic matter the vegetable 



1 ' Animals assimilate or absorb the organic substances which plants 

 have formed. They alter them by degrees ; they destroy or decom- 

 pound them. New organic substances may arise in their tissues, in 

 their vessels ; but these are always substances of greater simplicity, 

 more akin to the elementary state than those they had received. They 

 decompose, then, by degrees the organic matters created by plants. 

 They bring them back by degrees towards the state of carbonic acid, 

 water, azote, and ammonia, a state which admits of their ready resto- 

 ration to the air.' Dumas, loc. cit. p. 48. 



