NATURAL THEOLOGY. 307 



CHAPTER XVII. 



THE RELATION OF ANIMATED BODIES TO INANIMATE 



NATURE. 



We have already considered relation, and under 

 different views ; but it was the relation of parts 

 to parts, of the parts of an animal to other parts of 

 the same animal, or of another individual of the 

 same species. 



But the bodies of animals hold, in their consti- 

 tution and properties, a close and important rela- 

 tion to natures altogether external to their own: 

 to inanimate substances, and to the specific quali- 

 ties of these ; e. g., they hold a strict relation to the 

 ELEMENTS hy wMch they are surrounded. 



I. Can it be doubted, whether the ivings of birds 

 bear a relation to air, and ihe fins of fish to water ? 

 They are instruments of motion severally suited 

 to the properties of the medium in which the mo- 

 tion is to be performed ; which properties are dif- 

 ferent. Was not this difference contemplated 

 when the instruments were differently constituted? 



II. The structure of the animal ear depends for 

 its use not simply upon being surrounded by a fluid, 

 but upon the specific nature of that fluid. Every 

 fluid would not serve: its particles must repel one 

 another ; it must form an elastic medium : for it is 

 by the successive pulses of such a medium that the 



