350 



AVES. 



feather is a mechanical wonder ;" " their dis- 

 position, all inclined backward, the down 

 about the stem, the overlapping of their tips, 

 their different configuration in different parts, 

 not to mention the variety of their colours, 

 constitute a vestment for the body, so beau- 

 tiful, and so appropriate to the life which 

 the animal is to lead, as that, I think, we 

 should have had no conception of any thing 

 equally perfect, if we had never seen it, or 

 can now imagine any thing more so." 



Notwithstand- 

 ing the varieties Fig. 177.* 

 of size, consis- 

 tence,and colour, 

 all feathers are 

 composed of a 

 quill or barrel 

 (a, fig. 177), a 

 shaft (b b), and 

 a vane or beard 

 (c c) ; the vane 

 consists of barbs 

 (e e, fig. 178) 

 and barbules (ff, 

 fig. 178). 



The quill, by 

 which the feather 

 is attached to the 

 skin, is larger 

 and shorter than ^ 

 the shaft, is near- 

 ly cylindrical in 

 form and semi- 

 transparent; it 

 possesses in an 

 eminent degree 

 the opposite qua- 

 lities of strength 

 and lightness. It 

 terminates below 

 in a more or less 

 obtuse extremity, 

 which is pierced 

 by an orifice 

 termed the lower 

 umbilicus (e,fig. 

 177); a second 

 orifice, leading into the interior of the quill, 

 is situated at the opposite end, at the point at 

 which the two lateral series of barbs meet and 

 unite; this is termed the upper umbilicus (J\ 

 fig. 1 7?). The cavity of the quill contains a series 

 of conical capsules fitted one upon the other, and 

 united together by a central pedicle. 



The shaft is more or less quadrilateral, and 

 gradually diminishes in size from the upper 

 umbilicus to its distal extremity. It is always 

 slightly bent, and the concave side is divided 

 into two surfaces by a middle longitudinal 

 line continued from the upper umbilicus ; this 

 is the internal surface (c, fig. 178). The 

 opposite, or external surface (b, fig. 178), is 

 smooth, and slightly rounded ; both sides are 

 covered with a horny material similar to that 



* This figure and fy. 179, 180, 181, are copied 

 from the Monograph of F.Cuvier, '' Surle developpe- 

 ment des Plumes," Alemoires du Museum, torn. xiii. 



of which the quill is formed, and they inclose 

 a peculiar white, soft, elastic substance, called 

 the pith (a, fig. 178). 



Fig. 178 * 



-e 



Section of the Shaft and Vane magnified. 

 The barbs are attached to the sides of the 

 shaft near the external surface, and consist of 

 lamina, varying as to thickness, breadth, and 

 length. They are arranged with their flat sides 

 towards each other, and their margins in the 

 direction of the external and internal sides of 

 the feather ; consequently they present a con- 

 siderable resistance to being bent out of their 

 plane, although readily yielding to any force 

 acting upon them in the line of the stem : e e, 

 fig. 178, are the bases of the barbs of a 

 feather magnified. The barbules (ff, fig. 

 178) are given off from either side of the barbs, 

 and are sometimes similarly barbed themselves, 

 as may be seen in the barbules of the great 

 feathers of the Peacock's tail. 



Sometimes, as in these feathers and in the 

 plumes of the Ostrich, the barbules are long 

 and loose ; but more commonly they are short 

 and close-set, and by their form and disposition 

 constitute the mechanism by which the barbs 

 are united together. The barbules arising from 

 the upper side of the barb, or that next the 

 extremity of the feather, are curved downwards 

 or towards the internal surface of the shaft ; 

 those which arise from the under side of the 

 barb are curved in the contrary direction : so that 

 the two adjoining series of hooked barbules lock 

 into one another in a manner which the Pari- 

 sian dissectors compare to the fastening of a 

 latch of a door into the catch of the door-post. 



But besides the parts which constitute the 

 perfect feather, there is also an appendage 

 attached to the upper umbilicus of the quill 

 which requires to be noticed. This is termed 

 the accessory plume. It is usually a small 

 downy tuft, but varies both in different species, 

 and even in the feathers of different parts of 

 the body of the same bird. In the quill- 

 feathers of the wings and tail, it usually 

 remains in the rudimentary state of a small 

 tuft of down; but in the body-feathers of 

 Hawks, Grouse, Ducks, Gulls, &c. it is to 

 be found of all sizes, acquiring in some species 

 a size equal to that of the feather from which 

 it is produced. 



* Perrault, Hist. Nat. des Animaux, p. 336. 



