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 centre 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, the forearm, and the hand of man (Fig. 286). 

 When the wing is folded, the three divisions lie close 

 alongside one another. Fold your arm in the same manner. 

 The similarity of the bones.cf 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- 

 mals 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 



DC. I 



MCI 



0<*2 00.3 



Fj^. 287. — Hand and Wrist of Fowl 

 (after Parker). 



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

 CC. 3, wrist. 



1st. DIG* 



Jro.DIGi 



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

 Elbow of Young Chick (after Parker). 



