CLASS-BOOK OF ZOOLOGY. 



SECTION I. 

 INTRODUCTION. 



§ 1. Natural History is the science which treats sys- 

 tematically of all those bodies of which the earth is com- 

 posed, or which derive their sustenance from it. 



It is usually divided into three grand departments, 

 commonly called Mineralogy, Botany, and Zoology. 



§ 2. These divisions are based upon differences of 

 character and condition which distinguish the objects to 

 which they respectively relate. 



Rocks, earth, metals, etc., termed inorganic bodies, are 

 embraced in the science of Mineralogy. 



Trees, and all other kinds of plants, possessing the 

 principle of life, but deprived of both sensation and volun- 

 tary motion, form the particular province of Botany. 



Animals possessing life, voluntary motion, and sensa- 

 tion, are treated of in the science of Zoology. 



\ 3. All those bodies which are subject to growth 

 and decay, are called organic todies ; as animals and 

 plants. Mineral or inorganic substances are never in- 

 creased or diminished, except by the application of some 

 external force. In this respect they differ from animals 

 and plants. 



§ 4. Organic bodies are further distinguished from in- 

 organic by their power of reproducing, and hence of 

 perpetuating objects like themselves, or their own spe- 

 cies. Thus, from the seeds of plants, and the eggs of 

 animals, new plants and animals are produced. 



\ 5. As life is an essential condition of organic bodies 

 the instant they die, they become inorganic, and the mat 

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