THE VERTEBKAL COLUMN. 



Fig. 23. VIEWS OF DIFFERENT VERTEBRA FROM ABOVE TO ILLUSTRATE THEIR HOMOLOGIES 

 AND SOME OF THEIR VARIETIES. (Allen Thomson.) 



1, atlas ; 2, axis ; 3, fifth cervical ; 4, seventh cervical with supernumerary ribs ; 5, middle dorsal ; 

 6, first dorsal, with costal arch and sternum attached ; 7, third lumbar ; 8, first himbar with supernu- 

 merary ribs ; 9, fifth lumbar ; 10, first sacral ; 11, lumbo-sacral vertebra ; 12, fourth sacral vertebra in 

 a young subject ; 13, four coccygeal vertebrae. In the several figures the parts are indicated by letters 

 as follows, viz., in 1, s, spine ; n, neural arch ; c', the space occupied by the odontoid process, or dis- 

 placed centrum ; h. anterior arch ; ar, superior articular process ; in 2, c", odontoid process ; ar, superior 

 articular surface ; z', inferior articular process : in 3, c, centrum ; z, z' , superior and inferior articular 

 processes : in 4, t, transverse process ; r, vertebrarterial foramen ; co, moveable right supernumerary or 

 cervical rib ; x, with a dotted line marking the place where an anchylosed rib on the left side may be 

 considered to be superadded to the transverse process of the vertebra : in 5, t, transverse process with 



