INTRODUCTORY. VERTEBRAE. 



15 



In the higher vertebrates pads of fibro-cartilage the 

 intervertebral discs are commonly interposed between 



2-- 



10 



FIG. 2. CERVICAL VERTEBRAE OF AN Ox (Bos taunts). 



A, is the fifth; B, the fourth 



1. neural spine. 



2. transverse process. 



3. hypapophysis. 



4. convex anterior face of the 



centrum. 



5. concave posterior face of the 



centrum. 



C, the third. x (Camb. Mus.) 



6. prezygapophysis. 



7. postzygapophysis. 



8. vertebrarterial canal. 



9. neural canal. 



10. inferior lamella of transverse 

 process. 



successive centra, these or parts of them often ossify, especially 

 in the trunk and tail, and are then known as intercentra. 



The vertebrae of the higher forms can generally be arranged 

 in the following five groups, each marked by certain special 

 characteristics : 



1. The cervical or neck vertebrae. These connect 

 the skull with the thorax, and are characterised by relatively 

 great freedom of movement. They often bear small ribs, but 

 are distinguished from the succeeding thoracic vertebrae by 

 the fact that their ribs do not reach the sternum. The first 

 cervical vertebra which articulates with the skull is called 

 the atlas, but a study of the nerve exits shows that the first 



