FUNCTIONS AND INSTINCTS. 141 



maintain an equilibrium, and make good the 

 deficiency just stated. 



There is another function which is devolved 

 upon animals with respect to the vegetable 

 kingdom ; to keep the members of it within due 

 limits, and to hinder them from encroaching too 

 much upon each other. All organised beings 

 have a natural tendency to increase and mul- 

 tiply ; and while there is space this tendency is 

 beneficial ; but when plants or animals exceed 

 certain limits, they stand in each other's way, 

 and prevent all further growth or healthy pro- 

 gress. The herbivorous animals, in various 

 ways, serve as a countercheck to this tendency, 

 and keep the vegetable tribes from encroaching 

 too much upon each other. As I have detailed the 

 effects of this when I spoke of the ravages of the 

 locusts, and shall have occasion again to notice 

 it, I shall not now enlarge further upon it. 



I am next to consider another general function 

 of animals, or the effects they produce upon their 

 own body : and here the reason just alluded to, 

 their constant tendency to multiply so as to be 

 injurious to each other, and also to vegetable 

 productions, especially those that are important 

 to man or beast, which in the present state of 

 things is so constantly recurring, renders it 

 necessary that some bounds should be set to 

 their increase, which Providence effects by let- 

 ting them loose against each other. The great 



