46 



INTRODUCTION. 



Comparatice size of Quaifriipcds. 



2. J^umber and Distribution of Species. The number of species in the animal kingdom 

 has been estimated at about 100,000. Each genus is generally confined to a particular region 

 or climate, and where the same genus is found in diflerent continents the species are different. 

 Most of the domestic animals (the horse, cow, dog, sheep, goat, hog, and cat) thrive in nearly 

 every variety of climate, although some of them become more or less degenerate in high lati- 

 tudes. The camel and the elephant on the contrary cannot be naturalized in the colder climates. 



3. Zoological Regions. The earth appears to be divided into at least eleven zoological 

 regions or districts, of which each is the residence of a distinct set of animals ; 



(I.) The Arctic region contains several tribes common to the eastern and western con- 

 tinents, a circumstance owing doubtless to the communication between them afforded by means 

 of ice. (2.) The temperate regions of the eastern continent are inhabited by peculiar races, 

 quite distinct from the kindred tribes of the (3.) corresponding zone in the American continent. 

 The equatorial region contains four extensive tracts, widely separated from each other by seas, 

 and each peopled by distinct races ; these are (4.) the intertropical parts of Asia ; (5.) those 

 of Africa ; (6.) those of America ; (7.) the islands which constitute Malaysia ; and (8.) Pa 

 pua and the surrounding islands. (9.) . The extensive region of New Holland forms a distinct 

 zoological province, inhabited by several very singular tribes ; and the southern extremities (10.) 

 of America, and (11.) of Africa, separated from the northern temperate regions of their re- 

 pective continents by the heals of the torrid zone, are each distinguished by peculiar races. 



4. Jlnimals of Islands. The animals of islands situated near continents are in general the same 

 as those of the neighboring mainland. Small islands lying at a great distance from continents are 

 nearly or quite destitute of quadrupeds, except such as appear to have been carried to them by man. 



