UNITY OF LIFE 263 



they all perform the same fundamental functions. Moreover, 

 each organism is a unity in that the various functions are 

 somehow correlated, or harmonized. In the higher animals it 

 is the coordination and correlation of functions that most arouse 

 our wonder and interest. These harmonizing relations are 

 brought about by three special systems : 



1. The blood system. 



2. The gland system. 



3. The nervous system. 



317. All life is one. From experiments, from our own ob- 

 servations, and from this discussion we should now be able 

 to think of the unity of life in two distinct ways : 



1 . All life is one, in the sense that all organisms, large and 

 small, plant and animal, ancient and modern, useful and indif- 

 ferent and harmful, all live by virtue of doing certain things — 

 getting food, assimilating it after more or less change, liberating 

 energy, eliminating waste. They do other things, too ; but 

 these they all do, and all in ftmdamentally the same way. 



2. All life is one, in the sense that the many parts of an 

 organism, however they differ from one another, are alike in 

 their fundamental properties, and in the sense that they pro- 

 duce a unified series of activities. We can understand the 

 body, perhaps, only by understanding the parts ; but we care 

 nothing about the parts except as they have meaning for the 

 unity, for the whole. 



