76 INTRODUCTION. 



quill-coverts, are in most cases perfectly simple, although there 

 are some birds, especially among the Rasores, and, in particu- 

 lar, the Ptarmigans, which in those feathers have a very dis- 

 tinct rudimentary accessory feather, existing in the form of a 

 short tapering lamina, fringed along its free edges with small 

 simple barbs. 



Feathers, considered with regard to their uses, may be dis- 

 tinguished into two kinds. Those which are more especially 

 employed as the medium of locomotion, are much stronger, 

 more compact, and more elongated than the others. Of this 

 kind is the row of feathers bordering the wing behind, and that 

 terminating the coccygeal extremity or tail. The name of 

 quills ought to be applied to these latter, although it is usually 

 confined to the former. The feathers which lie immediately 

 over the wing-quills, on both sides of the wing, partake in this 

 respect of the nature of the quills themselves ; but those 

 which lie over the tail-quills are seldom, if ever, of so dense 

 a texture. ' 



In the feathers of many birds, the downy part. Fig. 20, c^ 

 occupies by far the greater portion ; in some it is merely the 

 tip that is compact, while in others the loose part is limited to 

 a very small extent, and in others scarcely exists. As an ex- 

 ample of feathers all downy, may be mentioned the subcaudal 

 feathers of the Peacock, and the abdominal feathers of Owls. 

 The Gallinaceous birds and Pigeons have a very large pro23or- 

 tion of down upon their feathers, although the latter are desti- 

 tute of the accessory plumule so highly developed in the former. 

 The crest-feathers of many birds are almost entirely destitute 

 of downy filaments, which is also the case with quills. In the 

 downy barb the filament or shaft is nearly equal in all its dia- 

 meters, and is extremely attenuated. The barbules are also 

 elongated in many of the Gallinaceous birds, for example, being 

 twenty times the length of the barbules of the apicial part of 

 the feather. These barbules are in all cases biserial like the 

 others, but very frequently they assume a direction the reverse 

 of these, coming off from the filament, not in the plane of the 

 web, but at right angles to it, or, in other words, from the face 

 and back of the web, so as to present on these surfaces a layer 



