NATURE AND NATURAL HISTORY 



§ 



When we are hard-pressed for an explanation of 

 natural phenomena we fall back upon the nature of 

 things. That is the final court of appeal. We can 

 take no step beyond that. It is a generalization so 

 vast that all the mysteries of creation may be hid- 

 den in it. The question of the nature of things is in- 

 volved in the question of the nature of the human 

 mind that speculates about the nature of things. 

 There is the nature of things, and there is the na- 

 ture of man. How are the two related? How do they 

 interact? Is not man a part of nature? What is com- 

 mon between a man and a rock, or a man and a 

 river, or a man and a tree, or a man and his horse, 

 or his dog? 



The same primary elements and forces are in all, 

 the same chemistry, the same physics. In all ver- 

 tebrate animals the metabolism is^ about the same, 

 and the ontogeny and philogeny. Protoplasm is 

 the physical basis of life in both the animal and the 

 vegetable; the cell is the unit of structure, the tree 

 breathes or takes in oxygen through its leaves, as 

 man through his lungs. The sunlight does for the 

 tree what it does not do for the animal; it enables 

 it to appropriate the carbon dioxide from the air. 

 This poisons the animal, but nourishes the plant. 

 Man must get his carbon through his food. The 

 vegetable world stands between him and the min- 

 eral. His only direct hold upon the world of non- 

 301 



