YE11TEBRAL COLUMN. 



rib. The body of the first dorsal vertebra is, however, distinguished by having 

 on each side a complete articular surface for the head of the first rib, besides 

 a smaller surface on the lower border for one facet of the second rib : the 

 lower costal surface on the tenth vertebra is usually complete for the tenth 

 rib ; and on the eleventh and twelfth there is only one articular surface on 

 each side for the corresponding ribs. 



The lamince, shorter and deeper than in the cervical vertebrae, are imbri- 

 cated or sloped one pair over another like tiles on a roof. The pedicles are 

 nearly on a level superiorly with the upper surface of the body ; and hence 

 the superior notches are very shallow, while the inferior notches are com- 

 paratively deep. 



The spinous process, described as bayonet-shaped, is three-sided, elongated, 

 and sloped, and terminates in a slight tubercle. It is longest and has the 

 greatest downward inclination in those towards the centre of the series ; 

 and in them the terminal tubercles are slender, while those of the upper 

 and lower vertebrae are thickened. 



The transverse processes are directed outwards and backwards, and present 

 in front of the extremity, which is enlarged into a rough tubercle, a small 

 surface for articulation with the tubercle of the rib. There is, however, no 

 such surface in the case of the eleventh and twelfth dorsal vertebrae. In 

 several of the lowest dorsal vertebrae there may readily be recognized on the 

 extremity of the transverse process, when looked at from behind, three 

 tubercular elevations, varying somewhat in form and size, and which are 

 named the external, internal, and inferior tubercles of the transverse pro- 

 cess. In the twelfth vertebra, in which the transverse process is extremely 

 short, those three tubercles are most fully developed. They correspond 

 respectively to the transverse, mammillary, and accessory tubercles after- 

 wards noticed in ihe lumbar vertebrae. (See Fig. 4, e, f, 6.) 



The articulating processes have their cartilaginous surfaces nearly verti- 

 cal. Those of the superior processes look backwards and slightly upwards 

 and outwards, those of the inferior processes look forwards and slightly 

 downwards and inwards. But the superior articular processes of the first 

 dorsal vertebra are similar to those of the cervical, and the inferior of the 

 twelfth dorsal to those of the lumbar vertebras. 



The ring is nearly circular, and is smaller than in the cervical or the 

 lumbar region. 



LUMBAR VERTEBRA. 



The lumbar vertebras are five in number. They are distinguished by 

 their great size and the absence of costal articulating surfaces. 



The body has a greater diameter transversely than from before back- 

 wards, and viewed from above or below its surface presents a reniforni 

 outline. That of the fifth lumbar vertebra has the distinctive character of 

 being considerably deeper at its anterior than at its posterior margin. 



The laminae are shorter, deeper, and thicker than those of the dorsal 

 vertebras. The superior notches are shallow, the inferior deep, as in the 

 dorsal vertebras. 



The spinous process, projecting horizontally backwards, is shaped like the 

 blade of an axe, but is thickened and rough along the edge which forms 

 its extremity. 



The transverse processes, long and compressed, with a superior and infe- 

 rior thin margin, project directly outwards. Their extremities lie in series 

 with the external tubercles of the lower dorsal transverse processes and 



