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THE BOOK OF NATURE STUDY 



a pair of stout pillar-like bones (coracoids) (Model C.), and the 

 horse-shoe like " merry-thought " or furcula (Model C. 10). 



The hind-limbs are supported by a great pelvis (Model C. 12). 

 The chief peculiarity of these limbs lies in their lower extremities. 

 There are no separate ankle bones for example. Of the two 

 rows of bones which make up this series, one row becomes welded 

 or fused with the " shank " of the leg (tibia) (Model C. 14), while 



FIG. 23. Upper surface of a bird's wing, prepared to show the relation of the large "quill" 

 or flight-feathers to the skeleton. A, the arm, of which the humerus forms the support. 

 F, forearm ; this contains two supporting rods, the radius and the ulna, the last-named 

 forming the support for the great flight or quill-feathers known as the secondaries, 

 i, 2, 3, 4, 5. H, the hand, containing the bones representing the thumb and 2nd and 3rd 

 fingers. The thumb bears four small stiff, quill-like feathers known as the bastard-wing. 

 The 2nd and 3rd fingers support the flight-feathers of the hand, marked 1-4. Of these 

 1-6 rest upon the bases of digits 2 and 3, 7 rests upon the tiny remnant of digit 3, and 

 conceals it ; 8, 9 and 10, n rest upon the penultimate and ultimate points of digit 2. The 

 narrow white band through which the bases of the quills pass represents a band of 

 tendon helping to keep the feathers in position. 



the other row is welded to the bones of the middle of the foot 

 (metatarsals) (Model .15). Of the original five toes but four 

 remain, and these answer to the great toe and succeeding toes of 

 the foot in man. 



