194 NATURAL THEOLOaY. 



CHAPTER XYII. 



THE RELATION OF ANIMATED BODIES TO INAN 

 IMATE NATURE. 



We have already considered relation, and under difierent 

 Tiews ; but it was the relation of parts to parts, of the parts 

 of an animal to other parts of the same animal, or of an- 

 other individual of the same species. 



But the bodies of animals hold, in their constitution and 

 properties, a close and important relation to natures alto- 

 gether external to their own — to inanimate substances, and to 

 the specific qualities of these ; for example, they hold a sti'ict 

 relation to the elements by which they are surrounded. 



I. Can it be doubted whether the wings of birds bear 

 a relation to air, and the fins of fiish to water ? They are 

 instruments of motion, severally suited to the properties oi 

 the medium in which the motion is to be performed ; which 

 properties are diflerent. Was not this difference contempla- 

 ted 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 oisuch a medium 

 that the undulations excited by the surrounding body are 

 carried to the organ — that a communication is formed be- 

 tween the object and the sense ; which must be done be- 

 fore the internal machinery of the ear, subtile as it is, can 

 act at all. 



III. The organs of voice and respiration are, no less than 

 the ear, indebted, for the success of tlieir operation, to the 

 peculiar qualities of the fluid in which the animal is im- 

 mersed They, therefore, as well as the ear, are constituted 

 upon the supposition of such a fljiid, that is, of a fluid with 

 such particular properties, being always present. Ohauffv- 



