OF VERTEBRAL COLUMN 



103 



behind, witli tlie posterior eonnrion ligament: laterally, with the short lateral; and 

 in the thoracic region with the interartieular and stellate ligaments. 



The anterior common ligament ( hgs. 194 and 200) commences as a narrow 

 hand attached to the under surface of the occipital bone in the median line, just 

 in front of the occipito-atlantal ligament, of which it forms the thickened central 

 portion. Attached firmly to the tubercle of the atlas, it passes down as the 

 central portion of the atlanto-axoidean ligament, in the mid-line, to the front of 

 the body of the axis. It no^v begins to widen out as it descends, until it is nearly 

 two inches (5 cm. ) wide in the lumbar region. . Below, it is fixed to the upper 

 segment of the sacrum, becoming lost in periosteum about the middle of that 

 ))one; but is again distinguishable in front of the sacro-coccygeal joint, as the 

 anterior sacro-coccygeal ligament. Its structure is bright, pearly-white, and 

 glistening with Avell-defined I»orders l)est marked in the thoracic region. It is 

 thickest in the thoracic region, and thicker in the lumbar than the cervical. It is 

 firmly connected with the bodies of the verteln-ee. and is composed of longitudinal 



Fig. 202. — Posterior Commox Ligament. (Lumbar region.) 



Median band 



Expanded lateral portion 



fibres, of which the superficial extend over several, while the deeper pass over only 

 two or three vertebra?. It is ctumected with the tendinous expansion of the prever- 

 tebral muscles in the cervical, and the crura of the diaphragm are closely attached 

 to it in the lumbar region. 



The posterior common ligament (figs. 198, 201, 202. and 209) extends from 

 the occi{)ital bone to the coccyx. It is Avider aljove than below, and commences by 

 a l)road attachment to the cranial surface of the V)asi-occipital. In the cervical 

 region it is of. nearly uniform width, and extends completely across the l)odies of 

 the vertebrae, upon which it rests quite flat. It does, however, extend slightly 

 further outwards on each side opposite the intervertebral discs. In the thoracic and 

 luml)ar regions it is distinctly dentated, being broader over the intervertebral suV)- 

 stances and the edges of the bones, than over the middle of the l>odies, where it is 

 a narrow band stretched over the bones without resting on them, some areolar 

 tissue and blood-vessels being interposed. The narrow^ median portion consists of 

 longitudinal fibres, some of which are superficial and pass over several vertebrae; 

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