FEATHERS. 17} 
by the aid of a small magnifying glass, in the quills of a Golden 
Eagle. 
Feathers, then, consist of three parts—the tube, the shaft, and 
the webs (Figs. 48, 49, 50); the webs being the barbs furnished with 
barbules, sometimes barbicels. They are convex above, and are thus 
enabled to resist flexion or fracture from beneath better than from 
any Other direction. They are also elastic; and this property, com- 
bined with their curvature, tends to keep them closer together. 
In the feathers of a large portion of birds there is a plumiform 
— 
OE 
\ 
\ 
\ 
\ \ \ 
Fig. 48.—Tube. Fig. 49.—Shaft. Fig. 50.—Web. Fig. 51.—Plume. 
formation (Fig. 51). The plumule is conspicuous in gallinaceous birds 
—for instance, the Pheasants (Fig. 52); it springs from the fore part 
of the tube, just at the commencement of the shafts; it gradually 
narrows, and is continued in the form of a very delicate, thread-like 
fibre ; from its side proceed two series of barbs, and from the barbs 
two series of barbules, extremely fine, entirely disunited, and very 
loose. This plumule seldom exists among aquatic birds, but in 
gallinaceous fowls it attains the length of two-thirds of the feather, 
and in the Emu and Cassowary it equals it in length. 
» Feathers may be divided into those specially employed as the 
means of locomotion and those intended to protect the Bird from 
extreme cold. The former are much stronger, more compact, and 
