COMPARATIVE ANATOMY 



thickened, and forms a main axis or stem (scapus), to which the 

 barbs are attached on either side. The proximal or basal portion of 

 the scapus which bears no barbs is called the quill {calamus), and 

 the distal part, to which the barbs are attached, the shaft (rachis). 

 The barbs together constitute the vane (vexilhim) (Fig. 14, F). 



TalISm 



Fiu. 14. — Six Stagks ix the L)EVELorMEXT of the Feathek. 

 (Mainly after Th. Studer.) 



Oil, dermis ; SM, stratum Malpighii ; /SV, stratmn corneum ; SiP, .S'c\ extensions 

 of these tissues into the featlier-papilla, Pap ; FK, feather-germ ; F, F\ 

 feather-follicle ; P, pulp ; Fal {SM^), folds of the Jlalpighian layer extending 

 into the feather-germ, and enclosed externally- by the horny layer, HS (.Sf^) : 

 both laj'ers are seen in the transverse section (0) ; F,Sp, quill of feather, which 

 breaks up above into a tuft of rays or barbs (SSf) ; sec, .str, secondary rays 

 (barbules) arising from the latter ; i?, rachis ; V, vexillum. 

 For further details as to the different stages A-F, compare text. 



The barbules are so arranged on each barb as to make the latter 

 resemble an entire feather in appearance. The barbs may become 

 very closely united together by means of minute hooks on the 

 barbules, so that an extremely strong and resistant though pliant 

 structure is formed ; this is especially the case in the large wing 

 and tail feathers (rcmiges and rcdriccs). 



In many Bird.s each quill of the ordinary feathers of the body bears two 

 ^•exilla, the second being spoken of as the (ifteishaft (hiijuDxichis). 



