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. 48.—Atlas and axis of Jabiru, separated. Fic. 49.— Atlas and axis of 
Jabiru, 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.t 
Let us compare the neck-bones with those of a reptile 
and a man. Although, as a whole, the bones of the 
* This bone is formed chiefly of two intercentra, which are small bones, 
very characteristic of reptiles (chevron-bones of the tail) and are not uncom- 
mon among the lower Orders of birds. 
7 In Hornbills the atlas and axis are fused together. 
