Feathers 37 



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. 



FIG. 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 



