CHAPTER VIII 



MOTHER EARTH 



Questions. 1. What do we mean when we say that *'man is made of 

 earth " ? 2. In what sense is this statement not true ? 3. What chemical 

 elements are present in the human body but not in plants ? 4. What 

 chemical elements are present in the human body but not in the earth ? 

 5. Are any elements present in the earth but not in the bodies of living 

 things ? 6. How cail people find out what substances are present in a 

 plant or animal? 



66. Man is made of earth. What does this statement mean ? 

 Our flesh and blood and our delicate nerves are very different 

 from the coarse materials of the earth, although the bones are 

 more easily likened to stones. Some people seem to picture to 

 themselves a clay image that is somehow suddenly inspired with 

 life, like the miracle of Galatea. Yet the statement is perfectly 

 true, and the process is as wonderful as any miracle, although 

 we understand many parts of it pretty well. " Man is made of 

 earth" because every particle in his body, like every particle in 

 the body of every other living thing, comes directly or indirectly 

 out of the soil out of the water, out of the air— the material 

 world in which we find ourselves. The food out of which we 

 build up our bodies comes directly from the bodies of other ani- 

 mals or from the bodies of plants. These other animals nearly 

 all derive their food from plants. The plants in turn build up 

 their bodies directly from three sources— water, air, and soil. 



67. The soil and the young plant. We saw that seeds can 

 sprout without depending upon the soil. Yet we know that the 

 soil is essential to the growth of plants, after the reserve in the 

 endosperm or cotyledons is all used up. 



We can plan experiments in which the various materials that 

 make up soil (such as sand, clay, and the various salts) are used 



91 



