VI ANIMALS AND PLANTS 169 



the exact researches of the modern chemical in- 

 vestigators of the physiological processes of plants 

 have clearly demonstrated the fallacy of attempt- 

 ing 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 gi^een 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 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 invah dated as the 

 third and second ; and even the first can be re- 

 tained only in a modified form and subject to 

 exceptions. 



But has the advance of biology simply tended 

 to break down old distinctions, without establish- 

 ing new ones ? 



With a qualification, to be considered presently, 

 the answer to this question is undoubtedly in the 

 affirmative. The famous researches of Schwann 



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 aiq)aratus which greeii plants possess exceeds that 

 absorbed in the concurrent respiratory process. 



