The Framew ork of the Bird 



91 



the adult bird the shifting backward of this bone until it 

 is parallel with the ischium is wholly an avian feature. 



^'''" '^'^■7lm,i''lo?- hi-'whl'?''* '" l^' back shows the great development of the 

 Uium toi bipedal locomotion in the sense of leaping ability. 



Wings 



We will now consider the framework of the fore limb, 

 or wing, of a bird, and a glance at the illustration show- 

 ing the arm of a man and the wing of a bird will at once 

 make plain the relation between the two. Here we again 

 find a great help in the fact that many of the bones keep 

 to their respective places in frogs, lizards, birds, and man. 



We know but little of the direct change from a fin to 

 a hand or foot, although there are some fishes living at 

 the present day with large finger-like bones in their pec- 



