VIL] ANIMALS AND PLANTS. 155 



stituent 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 sun- 

 shine and the animal, in so far as, under these circum- 

 stances, the green plant decomposes carbonic acid and 

 exhales oxygen, while the animal absorbs oxygen and 

 exhales carbonic acid ; yet, the exact researches of 

 the modern chemical investigators of the physiological 

 processes of plants have clearly demonstrated the 

 fallacy of attempting to draw any general distinction 

 between animals and vegetables on this ground. In 

 fact, the difference 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. 1 On the other hand, those plants, such as the 

 fungi, which contain no chlorophyll and are not green, 

 are always, so far as respiration is concerned, in the 

 exact position of animals. 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 



1 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 absorbed in the concurrent respiratory 

 process. 



