OUTLINES OF COMPARATIVE PHYSIOLOGY 

 AND MORPHOLOGY OF ANIMALS. 



INTRODUCTORY. 



SOME GENERAL PRINCIPLES. 



SECTION I. 



RELATIONS OF THE THREE KINGDOMS OF NATURE TO 

 ONE ANOTHER. 



Nature is primarily divided into two kingdoms, 

 the living and the nonliving. The living kingdom is 

 subdivided into the animal and the plant kingdoms, 

 thus : 



. (3. Animal. 



LlVln S j 2 . Plant. 



Nonliving 1 . Mineral. 



We may, indeed, divide Nature into three kingdoms 

 — mineral, plant, and animal — as seen above; but, if so, 

 it is necessary to remember that the gap between the 

 organized and the unorganized, the living and the non- 

 living, is far greater than between the two divisions of 

 the living kingdom, i. e., between plants and animals. 

 The study of unorganized or nonliving Nature belongs 

 to physics and chemistry; the study of organized or 

 living Nature belongs to biology. 



Living vs. Nonliving. — Besides the essential proper- 

 ties belonging to all matter, living things have certain 



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