FEATHERS OF BIRDS. 579 



While the construction of the feather, in its 

 different stages, is thus advancing from below, 

 those parts which are completely formed, are 

 rising above the surface of the skin, still enve- 

 loped in the capsule which originally protected 

 them, but the upper portions of which, from the 

 action of the air, and the obliteration of the 

 vessels that nourished them, now decaying, 

 shrivel and fall off in shreds, allowing the 

 successive portions of the feather to come forth, 

 and the laminae to unfold themselves as they rise 

 and assume their proper shapes. This succes- 

 sive evolution proceeds until the principal parts 

 of the stem and of the vane are completed ; and 

 then a different kind of action takes place. The 

 posterior part of the bulb now contracts itself, 

 and bringing the edges of that surface of the 

 stem closer together at length unites them at the 

 superior orifice (o), Fig. 228 ; where the laminae, 

 which follow these lines, also terminate. Having 

 thus performed the office assigned to it, it 

 ceases to be nourished, and is incapable any 

 longer of depositing a horny covering to the 

 feather : all that remains of its substance is a 

 thin membrane which adheres to the outside of 

 the tubular part or barrel of the quill, and which 

 must be scraped off before the latter can be 

 used as a pen. The tubular part is the product 

 of the anterior part of the bulb, which now 

 ceases to deposit the spongy substance, but 

 forms a transparent horny material over the 



