84 



GENERAL ORNITHOLOGY. 



Structure of Feathers. — A perfect feather, possessing all the parts it can have devel- 

 oped, consists of a main stem, shaft or scape (Lat. scapus, a stalk ; fig. 19, ad), and a supple- 

 mentary stem or after-shaft {hyporhachis ; Gr. vno, hupo, under, paxis, rhachis, a spine or ridge ; 

 fig. 19, ft), each bearing two webs or vanes (Lat. vexillum, pi. veodlla, a banner ; fig. 19, c, c, c), 

 one on either side. The whole scape is divided into two parts : one, nearest the body of the 

 bird, the tube or barrel or "quill" proper (Lat. calamus, a -reed), which is a hard, homy, 

 hollow, and semi-transparent cylinder, containing a little pith in the interior ; it bears no webs. 

 One end of this quill tapers to be inserted into the skin ; the other passes, at a point marked by 

 a little pit (Lat. timbilicus, the navel) into the shaft proper or rhachis, the second part of the 

 stem. The rhachis is a four-sided prism, squarish in transverse section, and tapers gradually 



to a fine point ; it is less 

 horny than the barrel, very 

 elastic, opaque, and solidly 

 pithy; it bears the vexilla. 

 The after-shaft, when well 

 developed, is like a duplicate 

 in miniature of the main 

 feather, fi-om the stem of 

 which it springs, at junc- 

 tion of calamus with rha- 

 chis, close by the umbilicus. 

 It is generally very small 

 compared with the main 

 part of the feather, though 

 quite as large in a few kinds 

 of birds ; it is entirely want- 

 ing in some groups of birds ; 

 it is never developed on the 

 large, strong wing- and tail- 

 feathers. The vane consists of a series of appressed, 

 flat, narrowly linear or lance-linear laminae or 

 plates, set obliquely on the rhachis by their bases, 

 diverging out from it at a varying open angle, end- 

 ing in a free point ; each such narrow, acute plate 

 is called a barb (Lat. barba, a beard ; fig. 20, a, a). 

 Now if these laminae or barbs simply lay alongside 

 each other, like the leaves of a book, the feather 

 would have no consistency ; therefore, they are connected together ; for, just as the rhachis 

 bears its vane or series of barbs, so does each barb bear its vanes of the second order, or little 

 vanes, called barbules (dimin. of barba; fig. 20, b, b, c). These are to the barbs exactly what 

 the barbs are to the shaft, and are similarly given off ft-om both sides of the upper edges of 

 the barbs ; they make the vane tridy a web, that is, they so connect the barbs together that 

 some little force is required to pull them apart. Barbules are variously shaped, but generally 

 flat sideways, with upper and lower border at base, rapidly tapering to a slender thready end, 

 and are long enough to reach over several barbules of the next barb, crossing the latter ob- 

 liquely. All the foregoing structures are seen by the naked eye or with a simple pocket lens, 

 but the next to be described require a microscope : they are the barbicels (another dimin. of 

 barba), also called cilia, or lashes (fig. 21); and hamuli, or booklets (Lat. hamulus, a little 

 hook; fig. 21). These are simply a sort of fi-inge to the barbules, just as if the lower edge 

 of the barbules were frayed out, and only differ from each other in that barbicels are plain hair- 



FiG. 20. — Two barbs, 

 a, a, of a vane, bearing an- 

 terior, b, b, and posterior, 

 c,barbules ; enlarged ; after 

 Nitzsch. 



Fig. 19. — A partly pennaceous, partly plum- 

 ulaceous feather, from Argus pheasant; after 

 Nitzsch. arf, main stem ; rf, calamus ; a, rhachis; 

 c, c, c, vanes, cut away on left side in order not 

 to interfere with b, the after-shaft, the whole of 

 the right vane of which is likewise cut away. 



