ARCHITECTURE NATURE-ACTION 185 



We need not enter into a technical discussion of 

 the differences between plant and animal life. They 

 are fully described in most text books of biology. Very 

 briefly stated, and without reference to well-known ex- 

 ceptions that do not seriously affect the general rule, 

 they are as follows: In plants, the living protoplasm 

 is enclosed in woody chambers, or cellulose walls, 

 through which only soluble foods may pass. In ani- 

 mals, these woody envelopes are absent and solid foods 

 may be taken into the body, and particles of suitable 

 size may pass freely into the living cells. Plants have 

 certain instruments, which, in cooperation with light, 

 transform inorganic solutions into living protoplasm. 

 Animals cannot do this. They must live on the prod- 

 ucts of the plant, or on other animals that live on plants ; 

 and their foods must be broken up, dissolved, and dis- 

 tributed in roundabout ways before they can be util- 

 ized in the construction of animal protoplasm. Plants 

 use carbon dioxide and liberate oxygen. Animals use 

 oxygen and give off carbon dioxide. Plants have no 

 muscles, nerves, and sense organs. These are the chief 

 instruments of animal life. 



These characteristic instruments of plants and ani- 

 mals rigidly restrict their respective manners of living, 

 but open to each resources unavailable to the other. To 

 the plant, they open to self-constructive usage the physi- 

 cal powers of heat and light and the chemical materi- 

 als of air and soil, but bind them to the soil, and to the 

 sun, for they are the sources of their nourishment. 

 The animal is restricted to plant products for its foods; 

 but it is free to move from place to place, sustaining 

 itself by rightly following the trails of countless subtle 

 influences which have no existence for the plant. 



