214 THE ORIGIN OF fLIFE 



the result of two opposing principles, the con- 

 structive and the destructive. 



In organic life this metabolism is always accom- 

 panied by the cellular structure. There are cellular 

 structures without metabolism, and there are meta- 

 bolic actions without cellular structure ; organic 

 life is the unique combination of these two. 



On the other hand, our idea of the cell admits 

 of considerable modification, and, as has been said, 

 the molecules themselves may be regarded as such 

 elementary bodies. With this extension the atoms 

 and molecules can be regarded also as the seats 

 of a certain amount of metabolic change. For 

 even the atoms themselves may be looked upon 

 as minute organisms of other and far smaller units. 

 In this way the continuity in the process is found 

 to exist, and many phenomena, strictly speaking 

 physical, would come under the realm of biology 

 by the striking resemblances which they thus ex- 

 hibit between physical and biological effects : as 

 links which serve to connect the organic with the 

 inorganic or living with apparently dead matter. 

 As we have said, the luminosity of flames, as 

 well as that of phosphorescent and fluorescent 

 bodies, appears to be due to the building up 

 and breaking down of highly complex molecular 

 aggregations, so that these too, it would appear, 

 come under the class of metabolic actions, although, 

 of course, of a far simpler kind than any which 

 take part in living processes as familiarly under- 

 stood. This idea of the mechanism of vitality 



