126 



GEiVERAL ORNITHOLOG Y 



Fig. 20. — Two barbs, a, a, 

 of a vane, bearing anterior, 

 b, b, and posterior, c, barb- 

 ules ; enlarged ; after 

 Nitzsch. 



in the interior ; it bears no webs. One end of this quill tapers to 

 be inserted into the skin ; the other jDasses, at 

 a point marked by a little pit (Lat. umhilims, 

 the navel) into the shaft proper or rhachis, the 

 second part of the stem. The rhachis is a 

 four-sided prism, squarish in transverse sec- 

 tion, and tapers gradually to a fine point ; it is 

 less horny than the barrel, very elastic, opaque, 

 and 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 junction of calamus 

 with rhachis, 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 wanting 

 in some groups of birds ; it is never develojied 

 on the large, strong wing- and tail-feathers. 

 The rave consists of a series of appressed, flat, 

 narrowly linear or lance-linear laminae or j^lates, 

 set obliquely on the rhachis bj^ their bases, diverging out from it at 

 a varying open angle, ending in a free point ; each such 

 narrow, acute plate is called a barb (Lat. barba, a beard ; 

 Fig. 20, a, a). Now if these laminre or barbs simply 

 lay alongside one another, 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 bai'bs 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 

 obliquely. All the foregoing structures are seen by p . oi 

 the naked eye or with a simple pocket lens, but the single barbuie, 

 next to be described require a microscope : they are the ceis 'and hook- 

 barblcels (another dimin. of barba), also called cilia, or |.^j*g^ . !j"f f'er 

 lashes (Fig. 21) ; and hamuli, or booklets (Lat. hamulus, Nitzsc'ii. 

 a little hook; Fig. 21). These are simply a sort of fringe to the barb- 



