BIRDS 



153 



The thigh hardly projects beyond the skin of the trunk, 

 as may be noticed in a plucked fowl. The thigh extends 

 forward from the hip joint (Figs. 286, 299) in order to bring 

 the point of support forward under the center of weight. 

 Why are long front toes more necessary than long hind toes ? 

 As the bird must often bring its head to the ground, the 

 hip joints are near the dorsal surface and the body swings 

 between the two points of support somewhat like a silver 

 ice pitcher on its two pivots. Hence stooping, which makes 

 a man so unsteady, does not cause a bird to lose steadiness. 



The wing has three divisions which correspond to the 

 upper arm, forearm, and hand of man (Fig. 286). When 

 the wing is folded, the three divisions lie close alongside 

 each other. Fold your arm in the same manner. The 

 similarity of the bones of the -first and second divisions to 

 the bones of our upper arm and forearm is very obvious 

 (Fig. 286). Ex- 

 plain. The hand of 

 a bird is furnished 

 with only three dig- 

 its (Fig. 287). The 

 three palm bones 

 (metacarpals) are 

 firmly united (Fig. 

 287). This gives 

 firmness to the 

 stroke in flying. 



That the bird is 

 descended from ani- 

 vials which had the 

 fingers and palm bones less firmly united is shown by 

 comparing the hands of a chick and of an adult fowl 

 (Figs. 287, 288). The wrist also solidifies with age, the 



DG.2 PQ.3 



Fig. 287. — Hand and Wrist of Fowl 

 (after Parker). 



DG. 1-3, digits: MC. 1-3, metacarpals; 

 CC, 3, wrist. 



Fig. 288. — Hand, Wrist (c), Forearm, and 

 Elbow of Young Chick (after Parker). 



