84 



GENERAL OEXITHOLOGY. 



..--W^S 



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

 opeil, cuusists of a main stem, shaft or scape (Lat. scapus, a stalk ; tig. 19. ad), and a supple- 

 mentary stem or after-shaft {hyporhachis ; Gr. iiro, hupo, under. pa\i.s. rhacltis. a spine or ridge : 

 fig. 19. h), each bearing two webs or vanes iLat. vexiUum,])!. rexilla, a banner; fig. 19, c, c, c). 

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

 bird, the tube or barrel or ■■quill" proper iLat. calamus, a reedi, which is a hard, horny, 

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

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

 a little pit (^Lat. umhUicus, the navel) into the shaft proper or rhaclus, the second piart of the 

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



to a fine pioiut ; it is less 

 horny than the liarrel, very 

 elastic, .ipaque. and solidly 

 piithy : it bears the vexiUa. 

 The after-shaft, when well 

 devehiped, is like a duplicate 

 in miniature of the main 

 feather, fi-oni the stem of 

 wliich it springs, at junc- 

 tion oi calamus u'ith rha- 

 chis, close by the umbihcus. 

 It is generally very small 

 compared with the main 

 part of tlie feather, tliough 

 quite as large in a few kinds 

 of birds ; it is entirely want- 

 ing in Some groups of birds ; 

 it is never developed ou the 

 large, strong wing- and taU- 



feathers. The vane cousists of a series of appresseii. 

 flat, narrowly linear or lance-linear lamina? or 

 plates, set obliquely on the rhacliis by then- bases, 

 diverging out from it at a varying i.>pen angle, end- 

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

 is called a barb (Lat. barba, a board ; tig. HO. a. a). 

 Xow if these lamina; or barbs shnply lay alongside 

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

 wnuld 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 seci>nd order, or little 

 vanes, called baibiiJiS (dimin. of barba : fig. :30, b, b, c). These are to the barbs exactly what 

 the barbs are to the shaft, and are similarly given ofi' fi-om both sides of the upper edges of 

 the barbs ; they make the vane truly a u-eb. that is. they so comiect the barbs ti-igcther that 

 some httle force is required to puU them apart. l>arliules are variously shaped, but generally 

 fiat sideways, with iq>per and lower border at base, rapidly t.apering to a sleuder 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 piicket lens, 

 but the next to be described require a microscope: they are tlie ?'(n-;)(cA- (another dimin. t'f 

 barba), also called e(7('<T, or lashes (fig. '21); and hamuli, or booklets (Lat. hamulus, a httle 

 hook; fig. ^1). These are simply a sort of fringe to the barbules, just as if the lower edge 

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



FlG. 20. —Two l.iirbs. 

 a, a. of a vane, bearing an- 

 terior, h, h. and posterior, 

 t', barbules ; enlargeil : after 

 ^"itzsch. 



Fig. 19. — -^ partly pennaceous. partly plum- 

 ulaceous feather, from Ar^us pheasant; after 

 Nitzscli. a(f. main stem I'/, calamtis; 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. 



