84 GENERAL ORNITHOLOGY. 
Structure of Feathers. — A perfect feat 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. t6, hupo, under, paxts, rhachis, a spine or ridge ; 
fig. 19, b), each bearing two webs or vanes (Lat. vexillum, pl. vexilla, a banner; fig. 19, ¢, ¢, ©), 
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, horny, 
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. wmbilicus, 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, from the stem of 
which it springs, at june- 
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- F1G. 20. — Two barbs, 
3 : : a, a, of a vane, bearing an- 
ing in some groups of birds; terior, 6,8, and_ posterior, 
it is never developed on the ¢,barbules; enlarged; after 
: ; Nitzsch. 
large, strong wing- and tail- 
feathers. The vane consists of a series of appressed, 
flat, narrowly limear or lance-linear lamine or 
plates, set obliquely on the rhachis by their bases, 
Fria. 19. — A partly pennaceons, partly plum- diverging out from it at a varying open angle, end- 
ee a ae cee eae ing ina free point: each such narrow, acute plate 
¢, ¢, c, Vanes, cut away on left side in order not 1S called a barb (Lat. barba, a beard ; fig. 20, a, a). 
Be cect eee eee of Now if these laming 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 from both sides of the upper edges of 
the barbs; they make the vane truly 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 hamuh, or hooklets (Lat. hamulus, a little 
hook; fig. 21). These are simply a sort of fringe 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- 
