80 ON THE CLASSIFICATION OF BIBDS. 
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 die same shape. 
(74.) The wings bear twosortsof feathers, liesides a diird 
series which lie 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 die 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 le-uer 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 five 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 
