Tira GROWTH OF A FEATHER. 35 



As the construction of the fcathei- proceeds from, below, those parts wliicli are 

 completely formed are rising above tlio surface of the skin. They are still en\elopcd in 

 the capsule which orio-inally protected them, but its upper portions now decay, shrivel, and 

 fall ofi' in shreds. Thus the successive portions of the feather are allowed to come forth, 

 and the laminrc to unfold themselves as they rise and assume their proper shapes. This 

 successive e\-olution proceeds until the jirincipal jDarts of the stem and 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, where 

 the laminae, which follow these lines, also terminates. Having thus performed its proper 

 office, it ceases to be nourished, and is incapable of depositing a hoi-nj' covering for the 

 feather. All that remains of its substance is a thin membrane, which adheres to the 

 outside of the barrel of the quill, and which must be scraped off before the latter can bo 

 used as a pen. 



The tubular part is the product of the anterior portion of the bulb, which now ceasing 

 to deposit the spongy substance, forms a transparent horny material over the whole 

 of its external surface. As it retires to the root, however, it leaves a succession of very 

 thin membranes, in the form of cones, which, when dried, form what is termed the pith 

 of the quill. The last remnant of the bulb is seen in the slender ligament which passes 

 through the lower orifice, and preserves the attachment of the feather to the skin. In 

 due time this also decays, and the whole feather is cast off, jjrcparatorj- to the formation 

 of another, which is to replace it in its season. All the feathers are, in general, moulted 

 annually, or at shorter periods-; and the same comjilicated process is begun and completed 

 by a new mould, produced for the occasion, every time a new feather is formed. 



