ZOOLOGY 



I. THE RELATION OF ANIMALS TO MINERALS, 

 TO PLANTS, AND TO ONE ANOTHER 



Most of us are familiar in a general way with animals 

 and plants, and with those inanimate objects we call 

 minerals. Yet not all of us, if asked suddenly, could tell 

 the difference between an animal and a piece of coal. It 

 would hardly do to say that the difference lies in the abiUty 

 of an animal to move from place to place while the piece 

 of coal cannot, because some animals cannot move about 

 any more than the coal ; for example, sponges, coral polyps, 

 etc. Moreover, there is a similarity between an animal and 

 a piece of coal of which we had perhaps never thought. 

 Either of them, if subjected to high heat for a sufficient 

 length of time, will be reduced to ashes. Since the ashes 

 to which plants and animals are reduced by heat con- 

 sist of mineral matters, it is evident that these organisms 

 are built up, partly at least, of mineral substances and to 

 this extent are similar to coal. 



This structural relation of plants and animals to minerals 

 is much more intimate than we are accustomed to think. 

 Plants take up mineral substances, — carbon, hydrogen, 

 and oxygen, — form starch from them, and use that starch 

 as food to build up vegetable tissue. Animals depend 

 largely for their food upon the starch and cellulose manu- 

 • factured and stored up by plants. Evidently, then, animals 



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