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Chapter X. 



VERTEBRATA CAPABLE OF FLYING. 



§ 1 . Vertehrata ivithoutFeathers, formed for flying. 



Few problems in mechanic art present greater 

 practical difficulties than that of raising from 

 the ground, and of sustaining and moving rapidly 

 through the air an animal body, composed as it 

 must be of many ponderous organs, that are re- 

 quisite for the performance of the higher func- 

 tions of life : yet Nature has achieved all this, 

 not only in endless tribes of the more diminutive 

 invertebrate animals, but also in the more solid 

 and massive organizations vrhich are modelled 

 on the vertebrate type. These objects have been 

 accomplished, in all cases, without the employ- 

 ment of any other than the ordinary elements of 

 those organizations ; modified, indeed, to suit 

 the particular purpose in view, but yet essentially 

 the same, and regulated by the same laws of 

 developement which prevail throughout the whole 

 animal system. The adaptation of these ele- 

 ments to the construction of an apparatus of so 

 refined a nature as that which is required for 

 flying, implies the deepest foresight, the most 



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