318 



SKELETON OF THE HOESE. 



This is the general number in all mammals ; even the long 

 neck of the giraffe has only the same number as the short 



neck of the pig.-' The 

 cervical vertebrae are 

 cubical in form, the first 

 two being modified. The 

 first is known as the 

 atlas (fig. 184), which is 

 simply a bony ring with 

 which the skull articu- 

 lates in front ; there is 

 no centrum to this ver- 

 tebra. The second ver- 



Fia. 183. —Axis. (Lateral view.) 



1, Superior spinoua process ; 2, odontoid pro- 

 Of'sR ; 3, intervfrtebral for.iTtien ; 4, body ; 5, in- . n j -i 



feiior spinous process ; 6, 7, inferior and superior tebra IS Called the oxis 



articulating processes. (Cijauveau.) , -, nn\ i - 



(fig. 183) : this is more 

 like a typical cervical ; but in front it has a projecting blunt 

 process coming from the centrum, the so-called odontoid pro- 

 cess (2), by which the axis can always be identified. The 



thoracic vertebrse number eight- 

 een, to which articulate the ribs. 

 The thoracic vertebrae have large 

 flat and broad neural spines, the 

 spines being longest in the an- 

 terior vertebrai in the region of 

 the horse's " withers," and direc- 

 ted baclvwards. The lumbar ver- 

 tebrse are six in number; they 

 are small and stout, with very 

 broad ^Ying-like lateral processes. 

 The sacral vertebrse, of which 

 there are five in the horse (ex- 

 cept in Arabs, which ha^'e six), are united in the adult into 

 one bony piece, the sacrum, which supports the pelvic arch. 



' Some Edentate mammals, such as the Three-toed Sloth-s, have a vary- 

 ing number of cervicals, some genera six, whilst others have nine. 



Fig. 1S4.— Atlas. (Inferior surface.) 



1, Articular cavities for condyles of 

 occipital bone ; 2, articular facet ; 3, ver- 

 tebral foramen ; 4, cervical foramen ; 6, 

 tr.ansverso process ; 6, inferior spinous 

 process; 7, superior arcii. (Chauveau.) 



