102 THEORY OF THE EARTH. 



quire i^rfairi proportions in the muscles which set 

 'ttienrJiJ mo.tioiiv and the impressions formed by 

 iiiese -lAH^oies cmust still farther determine the 

 forms of all these bones. 



After these observations, it will be easily seen 

 that similar conclusions may be drawn with respect 

 to the hinder limbs of carnivorous animals, which 

 require particular conformations to fit them for rar 

 pidity of motion in general ; and that similar con- 

 siderations must influence the forms and connexions 

 of the vertebrae and other bones constituting the 

 trunk of the body, to fit them for flexibility and 

 readiness of motion in all directions. The bones 

 also of the nose, of the orbit, and of the ears, re- 

 quire certain forms and structures to fit them for 

 giving perfection to the senses of smell, sight, and 

 hearing, so necessary to animals of prey. In short, 

 the shape and structure of the teeth regulate the 

 forms of the condyle, of the shoulder-blade, and 

 of the claws, in the same manner as the equation 

 of a curve regulates all its other properties; and, 

 as in regard to any particular curve, all its proper- 

 ties may be ascertained by assuming each separate 

 property as the foundation of a particular equa- 

 tion; in the same manner, a claw, a shoulder- 

 blade, a condyle, a leg or arm bone, or any other 

 bone separately considered, enables us to discover 

 the description of teeth to which they have be- 

 longed; and so also reciprocally we may determine 

 the forms of the other bones from the teeth. Thus, 



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