288 



SKELETON OF THE HORSE. 



numher. 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 cen'ical vertebrae are 

 cubical in form, the first 

 two being modified. The 

 first is known as the 

 atJcL--< (fig. 151), which is 

 .simply a bony ring with 

 which the skull articu- 

 lates in front ; there is 

 no centrum to this ver-. 

 tebra at all. The second 



Fig. 150. — Axiy. (Luteral view.) 



1, Superior spinous process ; '2, odontoid jiro 

 cess ; 3, intervertebral foramen ; 4, body ', 5, in- 

 ferior spinous process ; 6, 7, inferior and superior vertebra is called the Oxis 

 articulating processes. (Cliauveau.) 



(fig. 150) : this is moie 

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

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

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



thoracic vertelirte. 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 vertebi-cB in the region of 

 the horse's " withers," and direc- 

 ted backwards. The lumbar ve^ 

 tebrse are six in number; they 

 are small and stout, with very 

 broad wing-like lateral processes. 



Fig. 151. — Ati.as. (Inferior surface.) 



1, Articular cavities for condyles of 

 occipital bone ; 2, articular facet ; 3, vei"- 



tebral loranien ; 4, cervical foramen ; 5, j? l.- 1, 



tiansver.so process ; 6, inferior spinous Ihe Saci'al Vertebrfe, 01 WUlCtl 



proces; 



, superior arch. (Chauveau.) 



there are five in the horse (ex- 

 cept in Arabs, which have six), are united in the adult into 

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



^ Some Edentate m.ammals, such a« the Three-toed Sloths, have a vary- 

 icg number of cervicals, some genera sis, whilst others have nine. 



