THE BUILDING OF A BIRD 13 



" A bird does not row with his tail he steers with 

 it, as if it were a rudder ; and the long feathers are 

 therefore called rudder-feathers or rectrices, which is 

 Latin for rudders. But the short ones are called cov- 

 erts, like those of the wings upper tail-coverts, and 

 under tail-coverts." 



" How funny ! " said Dodo, " for a bird to have to 

 row himself and steer himself all at once. I know I 

 should get mixed up if I tried it with a boat. How do 

 feathers grow, Uncle Roy ? " 



" Just like your hair, little girl," said the Doctor, 

 patting her on the head, " or your nails. Didn't you 

 ever notice the dots all over the skin of a chicken ? 

 Each dot is a little hole in the skin where a feather 

 sprouts. It grows in a sheath that pushes out of the 

 hole, like a plant coining up out of the ground from its 

 root. For a while this sheath is full of blood to nour- 

 ish the growing feather ; that is why new feathers look 

 dark and feel soft pin-feathers they are called. The 

 blood dries up when the feather has unfolded to its full 

 size, leaving it light and dry, with a horny part at the 

 root that sticks in the hole where it grew, and a spray- 

 like part that makes up most of the feather. The 

 horny part becomes hollow or contains only a little dry 

 pith ; when it is large enough, as in the case of a row- 

 ing feather from a Goose's wing, it makes a quill pen to 

 write with. But the very tiniest feather on this Spar- 

 row is built up in the same way. 



"See! here is one," continued the Doctor, as he 

 twitched out a feather from the Sparrow's back. " You 

 see the quill part runs in the middle from one end to 

 the other ; this is called the shaft. On each side of it 



