Protoplasm. 



49 



chlorophyll are independent of organic compounds for their 

 nutrition, since they seize the solar energy and use it to 

 decompose the carbonic acid of the atmosphere. Oxygen is 

 returned to the atmosphere, carbon is retained, and, uniting 

 with the elements of water, is finally precipitated in the form 

 of some comparatively simple organic compound. This 

 being digested as required, and water, mineral matters, and 

 nitrogen being obtained from the soil by the roots, the re- 

 integration of new protoplasm is effected. 



As explained in section iv., the same destructive meta- 

 bolism exemplified by animals is also exhibited by plants, 

 but masked in great measure by constructive metabolism 

 where chlorophyll is present. 



There is thus in the economy ot nature a double 

 balance : 



(i) Between animal and vegetal life, or more strictly 

 between colourless and green protoplasm ; and (2) between 

 fresh and foul air, or more strictly between oxygen and 

 carbonic acM. 



Thi APct is so important in Biology that it warrants 

 repetition yet once mj^^n the diagrammatic form appended 

 which wieadil understood from the above 



NH, 



anima s 



and plants not 



possessing chlorophyll, 



which disintegrate 

 complex chemical com- 

 pounds, liberating 

 energy in the 

 process. 



Plants 

 possessing chlorophyll 



integrate complex 



chemical compounds, 



storing up solar energy 



in the process. 



They 



->NH 3 



\ 



<^. c Energy originally obtained from the sun 

 radiated by the animal (chiefly) into 

 space as heat, and thereby becoming 

 ultimately unavailable. 



