46 THE FUNCTIONS OF LIFE. 



crease can take place in their number, except by resorting 

 to the expedient which we find actually adopted, namely, 

 that of employing the substance of one animal for the nourish- 

 ment of others. Thus the identical combinations of ele- 

 ments, effected by the powers of vegetation, are transformed 

 in succession from one living being into another, and be- 

 come subservient to the maintenance of a great number of 

 different animals before they finally, by the process of de- 

 composition, revert to their original inorganic state. 



** See (lying" vegetables life sustain, 

 See life dissolving- veg-etate again; 

 All forms that perish other forms suppl)'-. 

 By turns we catch the vital breath and die." — Pope. 



Hence has the ordinance been issued to a large portion of 

 the animal world that they are to maintain themselves by 

 preying upon other animals, either consuming their substance 

 when already dead, or depriving them of life in order to pro- 

 Ions: their own. Such is the command given to the count- 

 less hosts of living beings which people the vast expanse of 

 ocean; to the unnumbered tribes of insects which every spot 

 of earth discloses; to the greater number of the feathered 

 race; and also to a more restricted order of terrestrial ani- 

 mals. To many has the commission been given to ravage 

 and to slaughter by open violence; others are taught more 

 insidious, though no less certain arts of destruction; and some 

 appear to be created chiefly for the purpose of quickly clear- 

 ing the earth of all decomposing animal or vegetable mate- 

 rials, which might otherwise have filled the air with noxious 

 exhalations and contaminated the sources of vitality.* 



This new law of animal existence must necessarily intro- 

 duce new conditions of organization and of functions. Struc- 

 tures adapted to rapid locomotion must be supplied for the 



* As especially appointed for the performance of this useful task may be 

 cited, among- the larger beasts of prey, the hyaena, the jackal, the crow, and 

 the vulture: among- marine animals, the Crustacea, and mimerous mollusca; 

 and among the lower orders, imiumerable tribes of insects, such as ants, 

 flesh flies, he. 



