300 



Elementary Biology. 



FlG. 162. A TYPICAL VERTEBRA 



(HUMAM). (Quain.) 



cord, and which therefore goes by the name of the spinal or 

 neural canal. From either side of the arch there projects 

 a longer or shorter process known as the transverse process. 

 It is to this process and to the body of the vertebra that the 

 ribs are articulated in those forms which possess ribs ; here, 

 however, ribs are absent. In addition we must note the 

 existence of facets or the points 

 of articulation of the successive 

 vertebrae on each other. There 

 are two facets in front and two 

 behind, also borne on the sides 

 of the arch. Vertebrae differ 

 from each other in size, in the 

 length and direction of the 



FIG. 161. A HAVERSIAN SYSTEM. 

 (Schafer.) 



v, vein ; a, artery ; /, lymphatic. 



:, centrum ; 2, arch ; 4, neural 

 canal ; 5, spinous process ; 6, 

 transverse process bearing facets, 

 f> 7, 7 1 ; c, c f , facets on centrum. 

 ( I he upper figure shows a vertebra 

 seen from before backwards, the 

 lower is a lateral view of the same ) 



transverse processes, and in other less important points. A 

 comparison of the vertebral column of the newt with that 

 of the frog shows that in the latter the tail vertebrae are 

 absent and that the last few vertebrae have coalesced into a 

 long fluted bone, the urostyle, in which, however, evidence 

 of the union can still be made out. 



