WHAT IS PHYSICAL LIFE 



we may say that muscle cells are much 

 less alive than the nerve cells in the spinal 

 cord, and these in turn much less alive than 

 nerve cells in the brain. 



But what is meant by the term, alive? 

 It is altogether too great a word to be 

 defined. An insect is alive, and a stone is 

 not. A little spider can make a web, which 

 nothing however great if it is not alive can 

 do. Only that which is alive can " make " 

 anything. Hence in the metazoa one form 

 is more alive than the other below it, and so 

 on through the whole series from a simple 

 living growth to living movement, and 

 then on to sensation, thought, and purpose. 



But this development of the metazoa 

 was very slow in its course, the slowest, 

 greatest, and last of all being nervous de- 

 velopment. We might almost liken it to a 

 prolonged course of education, each suc- 

 ceeding class learning what its predecessor 

 had, and then adding to it. 

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