ii.] THE SPINAL SKELETON; 3 i 



mentioned as correspondingly situate on the axis vertebra. 

 The upper pair of surfaces, which are larger and more 

 cup-shaped, articulate with two prominences on the base of 

 the skull. 



The atlas vertebra is formed to turn on the odontoid pro- 

 cess of the axis as on a pivot. This is further explained in 

 the Seventh Lesson of " Elementary Physiology." 



12. Having noted the characters of vertebrae above the 

 typical dorsal ones, those below (i.e. the lower dorsal and 

 lumbar) come next. 



The lower dorsal vertebrae have their centra larger than 

 those of the upper, while their transverse processes become 

 shorter, and their articular processes change their direction, 

 the upper zygapophyses looking obliquely inwards, the lower 

 ones obliquely outwards. Finally, their neural spines project 

 less downwards. 



In the. last dorsal vertebra a small rounded prominence 

 arises from the posterior margin of each upper articular 

 process. This prominence is termed the mammillary process, 

 or Metapophysis. 1 



Another small prominence projects backwards from 

 between the upper articular process and the transverse pro- 

 cess, and is called an Anapophysis. 2 



FIG. 43- A LUMBAR VERTEBRA. 



c, centrum ; s, neural spine ; /, tubercular process ; z, prezygapophysis ; 

 z', postzygapophysis ; Jit, metapophysis ; a, anapopnysis. 



The LUMBAR VERTEBR/E have their centra still more mas- 

 sive than the dorsal centra, and deeper in front than behind. 



The neural spines are all more massive, and project directly 

 backwards instead of downwards. 



The transverse processes are larger, and there are no tuber- 

 cular or capitular surfaces, and no process in the place of 

 the latter, as are found in the cervical vertebrae. 



i From MT, after, and apophysis. 2 From uv, backwards. 



