10 TWENTIETH CENTURY CLASSICS 



attached to the large central shaft that extends the entire 

 length of the feather. The barbs interlock with each 

 other by means of still smaller parts growing out from 

 them, giving the web a remarkable firmness. The inner 

 end of the feather terminates in the quill, which is con- 

 nected with the blood-vessels of the skin that supply it 

 with nourishment. They are moved by muscles just un- 

 der the skin and have a limited period of growth, when 

 they fall out and new ones appear. This gives rise to 

 the annual (sometimes oftener) moult. The duck family 

 lose their wing-feathers nearly all at the same time and 

 are hence unable to fly for a time. 



Feathers do not all answer to the above description. 

 Some, under the outer layer, are soft and fluffy because 

 the barbs of the web are not bound together by the little 

 hooks which we found on the wing-feathers. These are 

 called down-feathers. Then there are the long hair-like 

 forms plainly seen after " picking " a chicken, and which 

 are removed by singeing. These are called hairy feath- 

 ers, because they look so much like hairs. 



A singular fact about the. arrangement of feathers is 

 that they do not grow from every part of the skin that is 

 apparently covered by them, but grow in. tracts, so that 

 there are feather tracts and bare tracts. "If we com- 

 pare a bird's skin to a well-kept park, part woodland, 

 part lawn, where -they do not grow is the lawn." The. 

 ostrich and penguin are exceptions to this, for they have 

 a continuous feathering on every part of the skin. 



We are quite sure, too, that the bird's coat is warm, 

 making an excellent wrap. It serves him in this quite as 

 well as in flying, for his heart beats much faster than ours 

 and he requires more oxygen in proportion to his size than 

 we do ; and were it not for this warm coat, much of his 

 heat would be lost. 



