ii SKELETONS OF BIRD AND REPTILE 25 



unites with the sternum, and as the neck vertebra 

 bear small undeveloped ribs this is not an important 

 distinction. These neck ribs, short thin straight bones 

 pointing backward, can be seen in fig. 2 (CR, cervical 

 ribs) ; the two bases of each arc fused with the verte- 

 bra, and between them runs a tunnel through which 

 the vertebral artery passes. Besides this, the fore 

 limb has in some cases, very possibly, moved back- 

 ward, since the neck varies very greatly, far more 

 than the backbone, in the number of vertebrae that 

 compose it. 1 Where, then, is our fixed point ? 



I have already described the way in which the neck 

 vertebrae articulate. The next point to notice is their 

 large number, sixteen or seventeen being not un- 

 commonly found ; the Ostrich and the Swan having 

 considerably more : even small song-birds have not 

 less than ten. With mammals seven is the almost 

 invariable number, the neck of a Giraffe and of a 

 Hippopotamus being alike in this. A bird's neck, 

 to be supple and more than snake-like, must clearly 

 have a great many vertebrae. In the lizard eight is 

 the normal number. 



By far the most noticeable feature about the remainder 

 of a bird's vertebral column is its stiffness, due to the 

 fact that the vertebrae have become ankylosed together. 

 But it is quite erroneous to describe the bird's back- 

 bone as being throughout its length a rigid rod. In 

 all the specimens I have examined it bends, at a point 

 just in front of the pelvis, with some freedom to either 



1 The question is discussed by Max Fiirbringer in his 

 Morphologie und Systematik der Vogel, of which there is a good 

 summary in Nature, 1888-89. 



