Feathers a7 
quill—round where the body or body-feathers conceal 
it, square where it supports the vane,—and many other 
niceties which we can each detect for ourselves, show 
how exquisitely exact is the adaptation of a feather to 
its uses. 
Fic. 24.—Powder-down patch on the breast of a live Great White Heron. 
2/3 natural size. 
Growing from the under side of the quill, at the be- 
ginning of the vane, is a tiny feather known as the after- 
shaft. In an ordinary down-feather of a young bird this 
is of considerable size, but it is either small or entirely 
absent in an ordinary feather. It reaches its greatest 
development in the emeu and the cassowary, where it is 
