22 THE STRUCTURE AND LIFE OF BIRDS cuap. 
ties have been insurmountable when it has been 
attempted to show how many vertebre go to the 
skull, or to find in a bone of the skull parts that 
correspond to the easily distinguishable parts of a 
vertebra. The skull as yet presents many unsolved 
problems. For the present we must make a guarded 
statement that vertebrz to some extent enter into the 
formation of it. The bones of the jaw and those con- 
nected with them present problems of hardly inferior 
interest. But it will be time to give some account of 
them when we come to the subject of the embryo bird. 
The articulation of the skull with the neck will be 
described in the next chapter. 
The Vertebral Column. 
The bird’s neck bends with greater ease and freedom 
than the lizard’s. Indeed it outdoes even the supple- 
ness of the snake. If you hold up a snake by his 
tail, he tries to get at your hand, with a view to 
biting you if he is of a poisonous kind, by bending 
upward sideways. He has not much power of 
hollowing his back, so as to rise without a curve to 
the side. True, some snakes have much more supple- 
ness in an upward and downward direction than others. 
If the Hooded Snake is irritated, he raises the fore part 
of his body so that it forms a double curve or § shape. 
But even he cannot make by a long way so decided 
an § as a long-necked bird, and the reason is that in 
the bird the bones which form the neck articulate 
with each other differently, by a joint which is a 
marked improvement on the reptile’s joint. The 
