INTRODUCTION. y 



of the feather ceases to be grooved and a continuous horny cylinder 

 is formed which constitutes the quill. Shortly, a feather may be said 

 to consist of a tube or quill (calamus), a shaft, and two webs. The 

 tube or quill is horny and transparent, varies in length according to 

 the species, and is fixed in the skin. The shaft or rhachis is that part 

 above the quill which is filled with an elastic, corky, white buoyant 

 pith-like substance which bears the vane or web. It is coated on the 

 outer or generally convex side with a horny lamella not unlike the 

 tube, and on the inner or pithy side (also coated, though slightly) is 

 a well-defined groove along its length up to the umbilicus or the 

 small opening into the interior of the tube, which is closed inside by 

 dry membrane. On the side of the shaft, from above the quill or 

 tube, are vane rays or webs. These latter are, in general, fine, filiform, 

 and nearly cylindrical in the smaller feathers, and flattened in 

 the larger ones, as the quills. These, again, are furnished with 

 barbs, barbules and barbicels, which help to give coherency to the 

 entire web. 



Then there are the plumules or accessory plumes which, constructed 

 like the larger feathers issue from the margin of the quill tube below 

 the opening into the interior of the tube, which is regarded as an 

 appendage checked in its growth. This is inconspicuous in galli- 

 naceous birds, as pheasants. The plumules, unlike other feathers, have 

 the vane rays very delicate and fibre-like; two series of barbs issue 

 from them and from the barbs barbicels, extremely fine, entirely dis- 

 united, and loose. In the Cassowary and the Emu this plumula 

 accessoria is as large as the outer shaft and vane ; in others as Grouse 

 and Falcons, about three-fourths the length, downy and incoherent. In 

 the most well-developed feathers, as the quill feathers, the plumule is 

 not present, and in other altogether wanting throughout the whole of 

 their plumage, as in Strix, Columba, and Anas, while in song-birds 

 it is very minute and downy. 



Feathers may be divided into those which protect the bird from 

 extreme cold, and those specially intended for flight. Those 

 which are next the body, and commonly known as down, are 

 analagous to the under fur of quadrupeds. These keep the body in an 

 equal temperature, and may be said to resist cold or wet. 



