70 



ZOOLOGY. 



much wider range of motion being possible here than else- 

 where in the vertebral column. When the head is moved 

 up and down in a vertical plane, the skull moves 011 the 



atlas ; but when oblique in- 

 clination of the head takes 

 place, the skull and atlas 

 together are moved on the 

 odontoid peg. Simple side-to- 

 side motion involves bending 

 of the neck. By combination 

 of these three possible move- 

 ments the head can be turned 

 into a great variety of posi- 

 tions. 



Fig. 83. A LUMBAR VERTEBRA. 



Front view 6. The Lumbar Vertebrae 



(figs. 33 and 34) are seven 



in number, (except when the extra rib is present, when 

 they are only six). They are large, and have cleft trans- 

 verse processes, each giving rise to an ascending limb, the 

 metapophysis, and a descending one. The latter (generally 

 spoken of 

 as the trans- 

 verse pro- 

 cesses) 

 point steep- 

 ly down- 

 ward, and 

 are con- 

 siderably 

 longer than 

 those of 

 the thoracic 

 series. v 



Fig. 34. Two LUMBAR VERTEBRAE. 

 Sido view. 



7. The Sacral Vertebrae are strictly defined as those 

 whose transverse processes give articulation to the pelvic 

 girdle. On this definition there are only two sacral vertebrae ; 

 but when these become fused together a variable number 

 (two or more) of the next vertebrae behind also fuse with 



