THE THORACIC VERTEBRAE 



35 



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 l)y Lesbre to be the head of the axis. 



Occipital crest 



Median crest 



Paramastoid process I, /„,„./v'a^ 



Dorsal arch of atlas 



Anterior articular process of axis 



Intervertebra I for a m e n 



Foramen transversarium 



Post, articular processc 

 Ant. articular processe 



Transverse process 

 Dorsal crest — 



For a me n tra ns versa ri um 

 Post, articular processes 



Fig. 12. — Occipital Bone and First Three Cervical Vertebr.e of Horse, Dorsal View. (After Schmaltz, 



Atlas d. Anat. d. Pferdes.) 



THE THORACIC 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 



