162 ANIMALS AND PLANTS. 



widespread as a constituent of the skeletons of the lower 

 animals ; and it is probable that amyloid substances are 

 universally present in the animal organism, though not 

 in the precise form of starch. 



Moreover, although it remains true that there is an 

 inverse relation between the green plant in sunshine 

 and the animal, in so far as, under these circumstances, 

 the green plant decomposes carbonic acid and exhales 

 oxygen, while the animal absorbs oxygen and exhales 

 carbonic acid ; yet, the exact investigations of the mod- 

 ern chemical investigators of the physiological processes 

 of plants have clearly demonstrated the fallacy of at- 

 tempting to draw any general distinction between ani- 

 mals and vegetables on this ground. In fact, the dif- 

 ference vanishes with the sunshine, even in the case of 

 the green plant; which, in the dark, absorbs oxygen 

 and gives out carbonic acid like any animal.* On the 

 other hand, those plants, such as the fungi, which con- 

 tain no chlorophyll and are not green, are always, so far 

 as respiration is concerned, in the exact position of ani- 

 mals. They absorb oxygen and give out carbonic acid. 



Thus, by the progress of knowledge, Cuvier's fourth 

 distinction between the animal and the plant has been 

 as completely invalidated as the third and second ; and 



* There is every reason to believe that living plants, like living animals, 

 always respire, and, in respiring, absorb oxygen and give off carbonic acid ; 

 but, that in green plants exposed to daylight or to the electric light, the 

 quantity of oxygen evolved in consequence of the decomposition of carbonic 

 acid by a special apparatus which green plants possess exceeds that ab- 

 sorbed in the concurrent respiratory process. 



