LIGAMENTS OF THE VERTEBRAL COLUMN. 105 



odies of the vertebras and with the vessels, principally veins, 

 which separate its central from its lateral portions. By its ante- 

 rior or visceral surface it is in relation in the neck, with the longus 

 colli muscles, the pharynx and the 

 oesophagus ; in the thoracic re- Fig. 39.* 



gion, with the aorta, the venae 

 azygos, and thoracic duct ; and in 

 the lumbar region, with the aorta, 

 right renal artery, right lumbar 

 arteries, arteria sacra media, vena 

 cava inferior, left lumbar veins, 

 receptaculum chyli, the com- 

 mencement of the thoracic duct, 

 and the tendons of the lesser mus- 

 cle of the diaphragm with the 

 fibres of which the ligamentous fibres interlace. 



The posterior common ligament lies upon the posterior surface of 

 the bodies of the vertebrae, and extends from the axis to the sacrum. 

 It is broad opposite the intervertebral substances, to which it is 

 closely adherent ; and narrow and thick over the bodies of the ver- 

 tebrae, from which it is separated by the veins of the base of the 

 vertebrae. It is composed like the anterior ligament of shorter and 

 longer fibres which are disposed in a similar manner. 



Relations. The posterior common ligament is in relation by its 

 anterior surface with the intervertebral substances, the bodies of 

 the vertebrae, and with the venae basis vertebrae ; and by its poste- 

 rior surface with the dura mater of the spinal cord, some loose 

 cellular tissue and numerous small veins being interposed. 



The intervertebral substance is a lenticular disc of fibro-cartilage, 

 interposed between each of the vertebrae from the axis to the 

 sacrum, and retaining them firmly in connexion with each other. 

 It differs in thickness in different parts of the column, and varies in 

 depth at different points of its extent ; thus, it is thickest in the lum- 

 bar region, deepest in front in the cervical and lumbar regions, 

 and behind in the dorsal region; and contributes, in a great 

 measure, to the formation of the natural curves of the vertebral 

 column. 



ARCHES. The ligamenta sub/lava are composed of yellow elastic 

 tissue, and are situated between the arches of the vertebrae, from the 

 axis to the sacrum. From the imbricated position of the laminae 

 they are attached to the posterior surface of the vertebra below, and 

 to the anterior surface of the arch of the vertebra above, and are 

 separated from each other at the middle line by a slight fissure. 

 They counteract, by their elasticity, the efforts of the flexor muscles 



* The anterior ligaments of the vertebrae, and ligaments of the ribs. 1. The ante- 

 rior common ligament. 2. The anterior costo-vertebral or stellate ligament. 3. The 

 anterior costo-transvcrse ligament. 4. The interarticular ligament connecting the 

 head of the rib to the intervertebral substance, and separating the two synovial mem- 

 branes of this articulation. 



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