ATLAS AND AXIS 227 



sive centra are inserted pads of cartilage. The centra 

 and pads bear the weight of the body. On the centra 

 are also two cartilage-lined sockets which support a part 

 of the rib. 



The cervical vertebrae. — These are very similar to the 

 dorsal vertebra except for the absence of the rib articu- 

 lations. The transverse processes are poorly developed 

 and are perforated. The centrum is small, and the spinal 

 process short and often forked. They are specially devel- 

 oped to carry the head and give freedom of action. 



The lumbar vertebrae. — These are the largest of all 

 the vertebrae and have no rib attachments. Their spinous 



Fig. 87 — A, atlas ; B, atlas and axis ; a, b, articulations witli occipital bone ; 

 c, transverse ligament ; o, odontoid process. 



and transverse processes are short and stout, and well 

 adapted for the attachment of strong muscles. The heavy 

 centra allow them to support weight. 



Atlas and axis. — The two top cervical vertebrae have a 

 special function to perform, namely, to support the skull 

 and permit its free movement from right to left and for- 

 ward and back. To satisfy this requirement they show a 

 special modification. The top one, known as the atlas, 

 is fastened to the skull. It has a small centrum and a 

 large neural arch. This arch, or ring, is divided by a 



