80 



THE FLIGHT OF BIRDS 



take place. The rigidity there is more easily 

 brought about owing to the fact that of the two 

 small rows of wrist-bones the further one has been 

 fused with the hand-bones. When the fore-arm 

 is brought into line with the upper arm, the hand 

 also falls almost into line and is held tight in that 

 position by ligaments. As soon as the wing is 

 flexed at the elbow, it bends also at the wrist — 

 bends backward, that is, towards where digit 5 



MC 



Skeleton of wing of Adjutant (from the elbow). D 1, 2, 3 : 

 Digits 1, 2, 3. MC 1, 2, 3 : Metacarpals 1, 2, 3. R : Radius. 

 RC : Radial carpal. Ul : Ulna. UC : Ulnar carpal. The 

 marks left by the little pockets in which the secondary feathers 

 are planted can be seen on the ulna. 



would be if it existed — and then at the latter joint 

 much freer upward movement also is possible. And 

 so the wing is rigid when rigidity is wanted, and 

 pliant when pliancy is in demand {see fig. 23). 



