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ON THE CLASSIFICATION OF BIRDS. 



is only one small bone representing a finger, with the 

 vestige of two others. If, therefore, the human arm 

 was also an instrument of flight, it would present the ap- 

 pearance of the two figures in the last cut blended together. 

 The absence of digits or fingers to the carpus, or hand, 

 is supplied by the longest and most powerful of all the 

 wing feathers, which, by thus representing the enormous 

 fingers of the bat, bring the wings of both, however 

 differently constructed, nearly to the same shape. 



(74.) The wings bear two sorts of feathers, besides a third 

 series which He over the base of the humerus, and cover 

 that and the tertial quills. The first are those by which 

 the broad part of the wing is covered, and which serve 

 to protect and strengthen the base of the second series, 

 or the quills, which more especially are the instruments 

 of flight. We must consider each of these separately. 

 The first, which of course are the smallest, are called 

 the wing covers, and they are of three sorts, — the shoul- 

 der, the lesser, and the greater. They are disposed not 

 so much in an imbricate form as in rows ; so that the 

 outer web of one lies on the inner web of the next, and 

 so on. Those on the shoulder are the smallest : at 

 the edge or margin, adjoining the bones of the wing, they 

 are very small, each series gradually increasing in size, 

 and assuming more and more a parallel direction ; but 

 this disposition is not perfectly observable until we come 

 to the lesser covers, which consist of a single row of 

 feathers larger than any of the preceding, and which 

 are disposed in the manner just mentioned. The greater 

 covers immediately follow ; being, as their name de- 

 notes, larger than the last, but forming a single row, 

 and disposed in the same manner. Their use is ob- 

 viously to protect and strengthen the base of the most 

 important feathers belonging to the bird, which we shall 

 now notice. 



(75.) The quills constitute the greatest proportion 

 of the length of the wing, the longest being generally 

 four or rive times more developed than the greater co- 

 vers ; their length, however, is entirely regulated by the 

 situation they occupy with reference to the joints of the 



