74 INTRODUCTION. 



for the purjDOse of general description, as a perfect feather, is, 

 what is termed in botany, supra-decompound, there is yet in 

 feathers the following gradation in resj^ect to division : 



1^^. A feather may only have a tube and a shaft, without 

 any other part ; for example, the quill of the Cassowary. 



^dly. There are feathers which have a tube, a shaft, and 

 barbs destitute of barbules, as in the crest feathers of the Golden 

 Pheasant. 



Zdly. Feathers consisting of tube, shaft, barbs, and barbules ; 

 as in most birds. 



Attlihj. Feathers composed of tube, shaft, barbs, barbules, and 

 barbicels, as in the examples mentioned above. 



A barb also may have barbules in one part, and be simple 

 toward its extremity, which is a case of very frequent occur- 

 rence. 



Feathers, then, in general, consist of three parts, — the tube, 

 the shaft, and the webs ; or they may be primarily divided 

 into two parts, the tube and the vane, the latter of which con- 

 sists of the shaft and webs. The webs consist of barbs fur- 

 nished with barbules. 



With respect to the immediate consequences of their me- 

 chanism, it may be remarked of feathers in general, that, from 

 being convex above, they resist flexion or fracture more from 

 beneath upwards than in any other direction ; pulled to either 

 side also, they feel stronger than when bent downward in the 

 direction of their concavity. They are elastic, and this pro- 

 perty, together with their curvature, tends to keep them close 

 together, and enables the bird to present, when occasion re- 

 quires, a more or less compact surface to the air. When the 

 barbules are disjoined, they readily unite again, on being placed 

 in apposition. The weaker the feather is, provided it be com- 

 plete in all its parts, the greater is the cohesion between its 

 barbs. Compare, for example, the quills of the Golden Eagle 

 and Barn Owl. 



The webs ordinarily consist of united barbs, more or less 

 stiff, although elastic, and compact in their whole length, ex- 

 cepting toward the junction of the shaft with the tube, where 

 they are of a looser texture, often entirely disunited and float- 



