638 



BIRDS. 



The skeleton of the wing includes the stout humerus, the 

 separate radius and ulna (the latter the larger), two free 

 carpals, a carpo-metacarpus of three metacarpals fused to 

 one another and to some carpal elements, and three digits 



-the thumb with one joint, the first finger with two joints, 



the second with one. In adaptation to flight, the wing of a 



bird has much less flexibility of parts than the arm of a 



Mammal. The radius and ulna do not move upon each other. 



The pelvic girdle consists of dorsal ilia fused to the 



