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THE RELATION OF ANIMATED BODIES 
praise of invention and of successful thought: least of all 
could it ever be questioned, whether intelligence had been 
employed about it, or not. 
CHAPTER XVII. 
THE RELATION OF ANIMATED BODIES TO INANIMATE NATURE. 
We have already considered relation , and under differ¬ 
ent 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 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; e. g. they hold a strict 
relation to the elements by which they are surrounded. 
I. Can it be doubted, whether the wings of bh'ds bear 
a relation to air, and the fins of fish to water? They are 
instruments of motion, severally suited to the properties 
of the medium in which the motion is to be performed: 
which properties are different. Was not this difference 
contemplated, when the instruments were differently con¬ 
stituted ? 
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 medi¬ 
um, that the undulations excited by the surrounding body 
are carried to the organ; that a communication is formed 
between 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 their opera¬ 
tion to the peculiar qualities of the fluid in which the 
animal is immersed. They, therefore, as well as the ear, 
are constituted upon the supposition of such a fluid, i. e. of 
a fluid with such particular properties, being always pres¬ 
ent. Change the properties of the fluid, and the organ 
cannot act; change the organ, and the properties of the 
fluid would be lost. The structure therefore, of our or- 
