THE THORAX 



X039 



the elasticity of the vertebral column. The central portion of the 

 disc consists of a soft, elastic, pulpy substance, having a lobate 

 arrangement. Being surrounded and compressed on all sides by 

 the external laminar part, when a section of a disc is made the 

 pulp, being relieved from pressure, projects beyond the level of the 

 cut surface. It is composed of a cellular reticulum, supported by a 

 delicate fibrous stroma. 



The pulp is a persistent portion of the notochord. 



The intervertebral discs form about one -fourth of the length of 

 the vertebral colunm, and are thickest in the lumbar region. In 

 the cervical and lumbar regions they are deeper in front than be- 

 hind, and they give rise to the curve forwards in the cervical region, 

 whilst they increase the forward curve in the lumbar region. In 

 the thoracic region they are of uniform depth. Throughout the 



Fig. 431. — LIGAME^rTA Subflava in the Lumbar Region 

 (Anterior View) 



(The Pedicles have been sawn through, and the Vertebral Bodies removed). 



column they are intimately connected with the anterior and pos- 

 terior common ligaments, and, in the thoracic region, with the 

 anterior costo-central or stellate ligaments and the interarticular 

 ligaments of the heads of most of the ribs. In the cervical region 

 the discs are not present at either lateral aspect of the opposed 

 surfaces of the bodies. In these regions there is a synovial space 

 on either side, between the projecting lateral lip of the upper 

 surface of the lower body and the bevelled lateral margin of the 

 lower surface of the upper body. The opposed surfaces are covered 

 by cartilage, and there is an indistinct capsular ligament. 



2. Ligaments of the Laminse. — ^These are called the ligamenta 

 subflava. They are strong, thick plates of yellow, elastic tissue, 

 which connect the laminae together, and they extend from the axis 

 to the first sacral segment. They are best seen from the interior 



