The Audubon Societies 469 



reached their final growth, when they cease to be nourished from their base in 

 the skin and may be said to have become dead structures. As soon as they 

 become worn and unfit for use, they are displaced by new feathers that grow in 

 their stead ; and since the feathers of a bird, as we shall see, are fitted together 

 in a particular way, this displacement of old feathers by new ones takes place 

 regularly. Ordinarily we speak of this change of feathers as 'shedding 

 feathers,' or molting. 



Of all feathers belonging to a bird's pliunage, the quill or contour feathers 

 are the most symmetrically developed, especially the so-called 'flight-feathers' 

 which are found in the wings and tail. For this reason, we ^\dll take as a t>^e a 

 quill-feather, and study its general parts, omitting details that could not be 

 well understood without the use of a microscope. Two parts of such a feather 

 at once attract the eye, namely, the long, semi-transparent, somewhat horny 

 shaft, and the flexible feathery sides, or vane. The shaft is larger and conical at 

 the end where it is attached to the body, and this part is called the quill, while 

 the word shaft is used only in connection with the part which is somewhat 

 flattened, thinner, and angularly edged where the vane is attached. An easier 

 word to remember than vane possibly is vexillum, which means a pennant or 

 flag. Any one of you who has ever carried a flag knows that it has a wooden 

 shaft to which the flag or pennant part is attached, and that this shaft ends in 

 a handle. In similar fashion, a quill-feather, or any contour-feather, is made up 

 of a stiff supporting shaft with a handle and a flexible pennant. The entire 

 feather, it is needless to say, is very Hght. The expression 'of scarcely a feather's 

 weight' is familiar to everyone. 



So long as the feather is growing, it must have some place for nourishment 

 to enter. By looking carefully at the end of the quill, you can discover a tiny 

 hole, and if your eyes are very sharp you may find another on the inside of the 

 feather, where the quill flattens into the shaft. 



The vane, or vexillum, is far more complex than the quill and shaft. 

 Although it looks so smooth and whole, it is in reahty made up of thousands of 

 tiny parts. By running your fingers along the edges of the vane, you can easily 

 break it apart at any point, and when you do this, if your finger-tips are 

 sufficiently sensitive, you will feel a kind of rough, burlike surface. Starting 

 from the shaft, one might run a pin to the edge of the vane, as one can 

 between the teeth of a comb, and so break up the vane on either side of the 

 shaft into numberless pieces. Each of these pieces is called a harh. Seen under a 

 magnifying glass, a barb looks something like a tiny, lath-shaped structure, 

 ending in a point. Now each barb has a central stiffened part, supporting more 

 or less flexible parts on either side. Unlike the big general vane of the feather, 

 which is alike except in size on either side of the shaft, a barb carries two sets 

 of minute structures on either side of its central shaft, known as harhules, and 

 these, in turn, are further subdivided into barbicels, or hooklets. Since we can- 

 not see these without magnifying glasses, we wiU attempt to remember only 



