22 THE STRUCTURE AND LIFE OF BIRDS chap. 



ties have been insurmountable when it has been 

 attempted to show how many vertebrae 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 vertebrae 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 S shape. 

 But even he cannot make by a long way so decided 

 an 3 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 



