II 



LIVING MATTER 



55 



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 -^ 3 3 G QjgOrt 



energy of the sun's rays, as observed by J. E. Mayer (1845), plants 



reduce carbonic acid and form organic sub- , 



stances, which serve as fuel for the animals 



that constantly devour the plants and disperse 



the energy stored up in them. The plant is 



accordingly an apparatus for reduction, the 



animal an apparatus for oxidation. 



This theory was more particularly devel- 

 oped in France by Dumas and Boussingault, 



in Germany by Liebig. There is between 



plants and animals a constant circulation of 



matter and exchange of energy. The animal, 



by means of the oxygen of the air, transforms 



into heat, electricity, or motion the potential 



energy contained in the food-stuffs obtained 



directly (herbivores) or indirectly (carnivores) 



from plants, and produces water, carbonic acid, 



ammonia and salts. The plant draws these 



ultimate products from the air and soil, and 



by means of solar radiation builds them up 



into carbohydrates, fats, and proteins. Animal 



life as a 

 whole is 

 thus sub- 

 ordinated 

 to the pre- 

 existence 

 and co-ex- 

 istence of 



plant life, the latter being wholly 

 independent of the former. 



This doctrine of vital an- 

 tagonism between plants and 

 animals is no less false than the 

 teaching of Linnaeus and Guvier, 

 as was readily demonstrated by 

 Pniiger in 1875. It is a fallacy 

 to assume any radical difference 

 of function between plant and 

 animal protoplasm. In the last 

 chapter we saw that both kinds 



FIG. 12. Leaf of i)rosera roMdi/oZMi. (Darwin.) o f protoplasm differentiate into 



The leaf shows numerous peduuculated t 



glands, each having at its extremity a drop cells Ol* elementary OrgaillSlllS 



-' - '- - ''- -' ~ '"i catch anil digest j . -,-1 , -11 



endowed with an essentially 

 analogous structure and corn- 

 position. In considering the vital characters common to all 

 living beings we recognised both in plant and in animal metabolism 



Fie;. 11. Ascidium of leaf 

 of Ncjienthe-i. At the 

 bottom of the pitcher- 

 shaped receptacle is seen 

 the fluid F, secreted by the 

 glands, in which the ani- 

 malcules that fall in can 

 be digested. This figure 

 is somewhat reduced. 



