3,98 DISSECTION OF THE PIG-EON 



b. The vexillum, or vane, is the flattened portion of the 



feather, attached along the sides of the raohis. 



It is made up of barbs and barbules. 

 i. The barbs are a series of narrow, elastic laminae, 

 attached by their bases along the two sides of 

 the rachis. 

 ii. The barbules are much smaller processes, which 

 form fringes along the sides of the barbs : they 

 bear booklets, which hold together the adja- 

 cent barbs, and so give the feather that resist- 

 ance to the air on which the bird's power of 

 flight depends. 



c. The after-shaft is a miniature feather, attached to 



the ventral surface of the base of the rachis, and 

 overhanging the superior umbilicus. It is usually 

 very small, but is in some birds as large as the 

 primary feather. 



2. Varieties of feathers. 



a. The quill feathers are the large feathers of the wings 

 and tail : they are of two kinds, 

 i. The remiges, or wing-quills, have the inner or 

 posterior half of the vane much broader than 

 the outer or anterior half. They are divided 

 into groups in accordance with the bones to 

 which they are attached (fig. 67, p. 406). 



The primary quills are those attached to 

 the bones of the manus. They are eleven- in 

 number, of which six are attached to the 

 second metacarpal, and are hence called meta- 

 carpal quills : one, ad-digital, is attached 

 to the phalanx of the third digit ; two, mid- 

 digital, to the proximal phalanx of the second 

 digit ; and two, pre-digital, one of which is 

 small, are attached to the distal phalanx of 

 the second digit. 



The secondary quills are those attached to 

 the ulna. 



