72 



The Bird 



fellows and exactly suited to the requirements of its 

 position, but the first two following just behind the skull 

 are so radically unlike the others that we know at once 

 that they must serve some i)articular purpose. The first 

 is little more than a simple ring * of bone, and is called 

 the atlas, after the mythological giant who held up the 

 heavens upon his shoulders; named very aptly too, for 



Fig. 48. — Atlas and axis of Jabiru, separated. 



Fig. 49. — Atlas and axis of 

 Jal)irii, joined. 



this tiny collar of bone supports the skull itself. The 



next vertebra is ring-like too, but has a curious knob in 



front, which projects forward through the atlas and forms 



a pivot on which the head turns, hence its name, — the 



axis.f / 



Let us compare the neck-bones with those of a reptile 



and a man. Although, as a whole, the bones of the 



"■^= This bono is formed chief!}' of two intercentra, which are small hones, 

 very characteristic of reptiles (chevron-bones of the tail) and are not uncom- 

 mon among the lower Orders of birds. 



t III lioriibills the atlas and axis are fused together. 



