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 particular 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. 4S. — Atlas and axis of Jabiru, separated. 



Fig. 49. — Atlas and axis of 

 Jabiru, joined. 



this tin}^ 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 lx)ne is formed chiefly of two intercentra, whit-h are .■small hones, 

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

 mon among the lower Orders of birds. 



t Tn Hornbills the atlas and axis are fused together. 



