LIB E A II Y 



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MANUAL OF ZOOLOGY 



GENERAL INTRODUCTION. 



i. DEFINITION OF BIOLOGY AND ZOOLOGY. 



NATURAL HISTORY, strictly speaking, and as the term itself 

 implies, should be employed to designate the study of all 

 natural objects indiscriminately, whether these are endowed 

 with life, or exhibit none of those incessant vicissitudes which 

 collectively constitute vitality. So enormous, however, have 

 been the conquests of science within the last century, that 

 Natural History, using the term in its old sense, has of 

 necessity been divided into several more or less nearly related 

 branches. 



In the first place, the study of natural objects admits of an 

 obvious separation into two primary sections, of which the 

 first deals with the phenomena presented by the inorganic 

 world, whilst the second is occupied with the investigation of 

 the nature and relations of all bodies which exhibit life. The 

 former department concerns the geologist and mineralogist, 

 and secondarily the naturalist proper as well; the latter 

 department, treating as it does of living beings, is properly 

 designated by the term Biology (from )8ios, life, and Xo'yos, a 

 discourse}. Biology, in turn,, may be split up into the sciences 

 of Botany and Zoology, the former dealing with plants, the 

 latter with animals; and it is really Zoology alone which is 

 nowadays understood by the term Natural History. It should 

 also be borne in mind that the science which deals with those 

 forms of life which have existed during previous periods of the 

 earth's history to the present, and which is usually designated 



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