Bird Flight 183 



never will. He would not have the strength to wield 

 wings large enough to sustain so much avoirdupois on 

 the yielding air. 



The wings are highly specialized members of the avic- 

 ular organism, and hence differ in many important respects 

 from the fore or pectoral limbs of the mammals. Begin- 

 ning at the point nearest the body, let us examine one of 

 these wonderful instruments. The wing proper begins at 

 the shoulder joint, which hinges freely upon the shoulder 

 in a shallow socket, into which the globular head of the 

 first bone fits closely, and in which it is firmly held by the 

 powerful muscles that control the organs of flight. The 

 first bone is called the humerus, and is the largest and 

 strongest bone of the wing, extending from the shoulder 

 to the elbow. At the elbow, which is the first angle of 

 the wing, reaching backward when the wing is folded, the 

 humerus articulates in a wisely designed way with two 

 other bones, called the ulna and radius, which together 

 constitute the forearm and extend to the wrist joint. It 

 must be remembered that, when the wing is closed, the 

 forearm is the segment that reaches obliquely forward. 

 The wrist joint is the second angle of the wing. In the 

 wrist there are two small bones (the radiale and ulnare) 

 which serve an important purpose in joining the forearm 

 with what is known as the hand, and make possible the 

 specialized movement of the two parts upon each other. 

 The hand is the terminal segment of the wing, composed 

 of the metacarpal bones and the digits or fingers. Of the 

 last-named organs there are ordinarily three, forming a 



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