288 



SKELETON 01 THE HOKSE. 



number. 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. 151), which is 

 simply a bony ring with 

 which the skuU articur 

 lates in front ; there is 



Fig. 160.— Axis. (Lateral view.) nO centrum to this Ver- 



1, Superior spinous process ; 2, odontoid pro- tebra at aU. The secOlld 

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

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

 articulating processes. (Chauveau.) 



(fig. 150) : this is more 

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

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

 process (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 vertebra in the region of 

 the horse's " withers," and direc- 

 ted backwards. The lumbar ver- 

 tebrse are six in number; they 

 are small and stout, with very 

 broad wing-like lateral processes. 



Fig. 151. — Atlas. (Inferior surface.) 



1, Articular cavities for condyles of 

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

 tebral foramen ; 4, cervical foramen ; 5, i ^ • \. 

 transverse process ; 6, inferior spinous ihe sacral Vertebrae, 01 wnicn 

 process ; 7, superior arcli. (Chauveau.) , , ^ ■ , t i / 



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 mammals, such as the Three-toed Sloths, have a vary- 

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



