ANTERIOR LDIBS OF BIRDS, ETC. 99 



of the limbs, still we find in the latter, analo- 

 gous modifications to those presented by the 

 limbs of mammalia, and for the same obvious 

 reasons, to qualify the beings for certain modes 

 of life, and pecuhar habits. Difiering in ana- 

 tomical structure as the limbs of insects do, 

 from those of the vertebrata, still a burrowing 

 insect must have scrapers, and a swimming 

 insect paddles ; so we may say of the rest. At 

 the same time, as we have observed, we cannot 

 trace a, series of structural modifications from 

 the limbs of quadrupeds through those of 

 insects, because insects are modelled upon a 

 difierent type or pattern of organization en- 

 tirely. As in the Crustacea, their external 

 integument serves the purpose of a skeleton, 

 for there is no internal osseous framework. 



Concluding with these remarks, we shall 

 proceed to consider, as we proposed, the ex- 

 tent of the sense of tact or touch in the 

 vertebrata, a sense which, residing par excel- 

 lence in the hand of man, is transferred else- 

 where in the vertebrata below him. 



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