THE THORACIC VERTEBRA 



as 



Development. — The axis has six or seven centers of ossification. In addition 

 to the usual five, one or two appear for the dens, which is regarded as the displaced 

 body of the atlas. A nucleus behind the dens, which remains distinct to three or 

 four years of age, is considered by Lesbre to be the head of the axis. 



Occipital crest 



Median crest 



Paramastoid process 



Dorsal arch of a tins 



Anterior articular process of axis 



Intervertebral foramen 



Foramen transversarium 



Post, articular processes 

 Ant. articular processes 



Transverse process 

 Dorsal crest 



Foramen transversarium 

 Post, articular processes 



Fig. 12. — Occipital Bone and First Three Cervical Vertebra op Horse, Dorsal View. (After Schmaltr, 



Atlas d. Anat. d. Fferdes.) 



THE THORAQC VERTEBRA 

 These (Vertebrae thoracales) are usually eighteen in number in the horse, but 

 there are sometimes nineteen, rarely seventeen. As regional characters we note 

 the surfaces for articulation with the ribs and the length and form of the spinous 



