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Relationsnips or 

 tne Living Worla 



This book is about animals, those that are regularly called animals and 

 others, the human animals. The human ones descended from some now un- 

 known ancestors of the apes, developed language and mind with ideas and 

 became unique among all animals. It is about the relations of animals to one 

 another, and to the plants upon which they depend, to water, to the sun, and 

 to the earth about them. The organization and relationships inside and out- 

 side of animals are the keys to their existence. Inside, the secretion of a gland 

 in one part of the body is carried by the blood and stimulates the heart and 

 muscles in other parts. Outside, the seasons change, the woodchucks go into 

 their holes for the winter and the bobolinks fly south. 



Like the sun and the atmosphere and the soil, living organisms — the wood- 

 pecker in its hole in the pear tree and the fisherman and the fish — are composed 

 of atoms and molecules. For every organism, life is a concern of matter and 

 energy. It is not that its substances are so unusual; it is the way they are put 

 together that makes living matter different from everything else. 



Living matter occurs in cells. They are samples of its composition and 

 activity, units of the architecture of plants and animals, rosebush and man. To 

 the passing glance cells appear disarmingly simple although they are complex 

 far beyond our present understanding. In many-celled animals the bridge 

 over which all inheritable qualities pass to the next generation is in the con- 

 tent of two microscopic cells. By their union and the divisions which follow it, 

 the billions of cells in the body receive their quotas of inheritance. 



Plants and animals are bound together in a multitude of ways and the same 

 fundamental processes of living are common to both. A cactus is nearer to 

 human kin than a stone; the starvation of corn is not as spectacular as the 

 starvation of cattle, but it also is a disaster. 



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