126 



GENERAL ORNITHOLOGY 



PART II 



in the interior 



it bears ne 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. umbilicus, 

 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 

 PiG.2o.-Twobarbs,a,a, ^"^ ^°^^ S™ups of birds _; it is never developed 

 of a vane, bearing anterior, on the large, Strong wing- and tail-feathers. 



h, 6, and posterior, c, barb- rm • , p . p t ^ , 



uies ; enlarged ; after The vcine consists ot a Series of appressed, flat, 



^''^^*' narrowly linear or lance-linear laminse or plates, 



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



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



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



Fig. 20, a, a). Now if these laminse 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 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 



obliquely. All the foregoing structures are seen by _ 



the naked eye or with a simple pocket lens, but the sin^e' barbuiel 



next to be described require a microscope 



barbicels (another dimin. of barba), also called cilm, or 



lashes (Fig. 21) ; and hamuli, or booklets (Lat. hamulus, Nitzsch. 



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



FlG. 



ba 

 ,1 .-i bearing barbi- 



tney are the cels and book- 

 lets; magni- 

 fied; after 



