44 THE FUNCTIONS OF LIFE. 



setting up of temporary structures, which are 

 required only at an early stage of growth, and 

 which are afterwards removed to give place to 

 more permanent and finished organs. 



The utmost solicitude has been shown in every 

 part of living nature to secure the perpetuity of 

 the race, by the establishment of laws, of which 

 the operation is certain in all contingent circum- 

 stances. It has also been manifestly the object 

 of various provisions to diffuse the races as 

 widely as possible over a great surface of the 

 habitable globe. 



We are next to advert to the important conse- 

 quences which, in the animal kingdom more 

 especially, flow from this law of indefinite pro- 

 duction. As animals are ultimately dependent 

 on the vegetable kingdom for the materials of 

 their subsistence, and as the quantity of these 

 materials is, in a state of nature, necessarily 

 limited by the extent of surface over w hicli vege- 

 tation is spread, a time must arrive when the 

 number of animals thus continually increasing 

 is exactly such as the amount of food pro- 

 duced by the earth will maintain. When this 

 limit has been attained, no farther increase 

 can take place in their number, except by re- 

 sorting to the expedient which we find actually 

 adopted, namely, that of employing the sub- 

 stance of one animal for the nourishment of 

 others. Thus the identical combinations of ele- 



