106 



The Vertebrate Organ Systems 



condyles of the skull. The second vertebra, the axis, has a projection 

 from the anterior surface of the centrum, the odontoid process, 

 which fits into the ring of the atlas, and provides a pivot on 

 which the skull turns. 



The thoracic vertebrae are easily distinguished because of the tall, 

 backward projecting neural spines and the surfaces for rib attachment. 



The heavy transverse processes for the attachment of the large 

 thigh muscles characterize the lumbar vertebrae (Fig. 32). These proc- 

 esses are directed forward. The neural spines are rounded rather 

 than pointed. 



neural spina 



Fig. 32. — Vertebrae and ribs. A, Rib movements in breathing; B, rib articula- 

 tion, siiowing pivot points (P); C, a lumbar vertebra from above; D, lumbar ver- 

 tebra, lateral view. (By permission from Man and the Biological World by Rogers, 

 Hubbell, and Byers, copyright 1952. McGraw-Hill Book Company, Inc.) 



