VERTEBRAL COLUMN 



187 



The last three have accessory processes also. The first three or four spinous proc- 

 esses are about equal in length. Behind this they become gradually shorter to the 

 tenth, and then remain equal. The backward slope is most marked in the ninth 

 and tenth. The eleventh is practically vertical (anticlinal vertebra), and the last 

 two incline slightly forward. 



The bodies of the seven lumbar vertebrae are decidedly flattened dorso-ventrally 

 and mcrease in width from first to last. The length increases to the sixth. The 

 transverse processes are plate-like and are directed forward and downward Their 

 length increases to the fifth and sixth. They form no joints ^vith each other or 

 with the sacrum. ■ Their extremities are enlarged, with the exception of the last. 

 The accessory processes project backward over the posterior notches of the first 

 five. The anterior articular processes are large, compressed laterally, and bear 

 mammillary processes. The spinous processes are broad below, narrower above, 

 and mth the exception of the last, incline a little forward. Their height diminishes 

 behind the fourth. 



The sacrum results from the early fusion of three vertebrs. It is short, 



"Fig. 206. — Fifth Lumbar \'ertebra of Dog; Dorsal View. 

 1, Anterior end of body; 2, spinous process; 3, 3', artic- 

 uJar processes; 4, transverse process; 5, accessory process; 

 6, groove for spinal nerve. 



Fig. 207. — Sacrum of Dog; Ventral View. 

 J, II, III, Bodies of vertebrae; 1, 2, ventral sac- 

 ral foramina; 3, 4, lineae transverste; 5, anterior end 

 of body of first sacral vertebra; 6, 6', anterior artic- 

 ular processes; 7, 7', wings; 8, posterior end of body 

 of last sacral vertebra ; 9,9', posterior articular proc- 

 esses; 10, sacral canal; 11, spinous [process; 12, 

 12', transverse processes; 13, auricular surface. 



wide, and quadrangular. The spines are fused to form a median crest, which is 

 notched, however, between the summits of the spines. On either side are two 

 tubercles, vestiges of the fused articular processes. The pelvic surface is deeply 

 concave and presents two pairs of foramina. The wings are prismatic and very 

 high. Their lateral surfaces are extensive, face almost directly outward, and bear 

 an auricular surface on the lower part. The anterior surface of the body of the 

 first vertebra is extensive, depressed in its middle, and bears a prominent lip below. 

 The anterior articular processes are large and have extensive, slightly concave 

 facets which face dorso-medially. The posterior articular processes are small. 

 The transverse processes of the last vertebra project backward and may articulate 

 or fuse with those of the first coccygeal. The sacral canal is strongly compressed 

 dorso-ventrally. 



The coccygeal vertebrae are fully developed in the anterior part of the region. 

 The arch is complete in the first six usually. The first three or four have well de- 

 veloped articular processes at each end. Behind this the posterior processes 

 quickly disappear, and the anterior ones become non-articular and gradually re- 



