96 STRUCTURE OF BIRDS. 



LESSON XV. 



STRUCTURE OF BIRDS WINGS, LUNGS, CROP, 



FEATHERS, ETC. 



THE frame of birds is very beautifully adapted 

 to their habits. Many of them pass a great portion 

 of their time in the air, either in the pursuit of 

 their prey, or in sportive gambols, and in these we 

 find every part of the body framed as lightly as 

 possible. In order to enable them to glide easily 

 along, all their feathers lie one way, pointing 

 backwards, and folding over each other in. regular 

 order. No resistance is offered to their flight by 

 this arrangement, whilst beneath these there is a 

 layer of soft down, which preserves them from 

 cold, to the effects of which, but for this provision, 

 they would have been much exposed. 



The wings of birds are the means by which they 

 support themselves, and contain the largest and 



