34 INTRODUCTION. 



plane. These solid parts are moved upon each other, and upon 

 the scapula, hy a complicated muscular apparatus ; and the 

 arm, thus constructed, is converted into an instrument of flight 

 by having appended to its posterior edge a large lamina or plate, 

 composed of a series of strong, elastic feathers, named quills, 

 and varying in firmness, form, length, and relative proportion, 

 according to the kind of flight necessary for the species. When 

 about to be employed, the parts, which in a state of rest vrere 

 folded up, are stretched out so as to unfold the feathers some- 

 what in the manner of a fan, and form a horizontally expanded 

 lamina, which being alternately raised and forcibly pulled down, 

 furnishes a lever by which the body is elevated into the air ; 

 when, by repeated strokes, by which the wing is alternately 

 drawn upwards, forwards, and inw^ards, and then more forcibly 

 outwards, downwards, and backwards, the bird advances, direct- 

 ing its course by the tail, but more especially by a difference 

 in the action of the two wings. 



In Plate II. is represented the wing of a domestic Pigeon, 

 Columba Livia^ deprived of all its feathers excepting the quills, 

 and viewed, first from above. Fig. 1 ; then from beneath. Fig. 

 2. In these figures, «, is a portion of the body ; ^, c, the 

 humerus ; (?, d^ the cubitus ; d^ e^ the carpus and metacarpus ; 

 ^, /, the digital bones ; ^, the poUex. The ten quills attached 

 to the hand, from d to /, are the primary quills ; those at- 

 tached to the cubitus, from c to c?, are the secondary quills. 

 They are arranged, as is observed, in two distinct sets. Those 

 on the first finger, g^ are named the alula, or spurious wing : 

 they are few, and of small size. Besides these, there are large 

 feathers, not however so strong, attached to the skin along the 

 edge of the humerus, ^, c ; but these, which are named tertiary 

 quills, have been removed. Now the order of nomenclature, 

 if numerical, ought to have commenced at the part nearest the 

 body ; those on the first joint or brachium, ought obviously to 

 have been named primary ; those on the second, secondary ; 

 those on the third, tertiary. A decidedly preferable mode, 

 however, is to name the quills according to their relations : 

 those on the arm, brachial ; on the fore-arm, cubital ; on the 

 hand, digital ; on the outer finger, alular. 



