64 THE VITAL FUNCTIONS. 



the same never ending cycle of vicissitudes and 

 transmutations. 



The diffusion of animals over wide regions of 

 the globe is a consequence of the necessity which 

 prompts them to search for subsistence wherever 

 food is to be met with. Thus while the vegetation 

 of each different climate is regulated by the sea- 

 sons, herbivorous animals are in the winter forced 

 to migrate from the colder to the milder regions, 

 where they may find the pasturage they require; 

 and these migrations occasion corresponding 

 movements among the predaceous tribes which 

 subsist upon them. Thus are continual inter- 

 changes produced, contributing to colonise the 

 earth, and extend its animal population over 

 every habitable district. But in all these changes 

 we may discern the ultimate relation they ever 

 bear to the condition of the vegetable world, 

 which is placed as an intermediate and necessary 

 link between the mineral and the animal king- 

 doms. All those regions which are incapable of 

 supporting an extensive vegetation, are, on that 

 account, unfitted for the habitation of animals. 

 Such are the vast continents of ice, which spread 

 around the poles ; such are the immense tracts 

 of snow and of glaciers, which occupy the sum- 

 mits of the highest mountain chains ; and such 

 is the wide expanse of sand, which covers the 

 largest portions both of Africa and of Asia : and 

 often have we heard of the sunken spirits of the 



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