§ 15. 



GENERAL INFERENCES. 145 



The enamel is unequally distributed round the tooth, being 

 very thin behind and thick in front, by which means the 

 cutting edges are always preserved; for by the act of 

 gnawing, the hinder part of the incisor wears away quicker 

 than the fore part, and thus a sharp inclined edge, like that 

 of an adze or chisel, is maintained, and which is the very 

 form required in the economy of the animal. The teeth of 

 the common rabbit or hare will exemplify these remarks. 



15. General inferences. — These are but a few in- 

 stances of those admirable adaptations of means to ends, 

 which are observable throughout the various classes of 

 organized beings : but the limits of a single lecture will not 

 admit of more examples, and it is, I trust, unnecessary 

 to offer additional proofs, that the conclusions of geologists 

 as to the nature of the ancient inhabitants of our globe, are 

 not vague assumptions, as those unacquainted with the 

 science might suppose, but the legitimate deductions of 

 laborious and patient investigations. A few teeth and 

 bones — sometimes but a single relic of this kind — are the 

 elements by which the palaeontologist is enabled, not only 

 to restore the forms of creatures now banished from the 

 face of the earth, but also to ascertain their habits and 

 economy, and even arrive at positive conclusions respecting 

 the nature of the country of which they were once the 

 inhabitants. If we find the remains of animals which were 

 herbivorous, it follows that there must have been a condi- 

 tion of nature calculated for the growth of vegetable pro- 

 ductions for their subsistence ; a suitable soil and climate, 

 and a country diversified by hills, valleys, and plains, with 

 streams and rivers to carry off the superfluous waters. 



The same laws, under certain modifications, apply to 

 other classes of beings. In birds, the form of the feet is 

 modified according to the habits of the different orders. 

 In the parrot, (Lign. 22, fig. 3,) the claws are adapted to 

 climb trees and perch on the branches; but in the eagle 



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