58 THE VITAL FUNCTIONS. 



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 move- 

 ments among the predaceous tribes which subsist 

 upon them. Thus are continual interchanges pro- 

 duced, contributing to colonize the earth, and ex- 

 tend 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 inter- 

 mediate and necessary link between the mineral 

 and the animal kingdoms. All those regions, which 

 are incapable of supporting an extensive vegeta- 

 tion, are, on that account, unfitted for the habita- 

 tion 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 oc- 

 cupy the summits of the highest mountain chains ; 

 and such is the wide expanse of sai^d, which covers 

 the largest portions both of Africa and of Asia : 

 and often have we heard of the sunken spirits of 

 the traveller through the weary desert, from the 

 appalling silence that reigns over those regions of 

 eternal desolation ; but no sooner is his eye re- 

 freshed by the reappearance of vegetation, than 

 he again traces the footsteps and haunts of ani- 

 mals, and welcomes the cheering sound of sensi- 

 tive beings. 



The kind of food which nature has assigned to 

 each particular race of animals has an important 

 influence, not merely on its internal organization, 



