ARTICULATIONS OF THE VERTEBRAL COLUMN 



271 



centre. The outer layers of the disk are arranged concentrically one within the other, the outer- 

 most consisting of ordinary fibrous tissue, but the others and more numerous consisting of white 

 fibrocartilage. These plates are not quite vertical in their direction, those near the circumference 

 being curved outward and closely approximated; while those nearest the centre curve in the 

 opposite direction, and are somewhat more widely separated. The fibres of which each plate is 

 composed are directed, for the most part, obliquely from above downward, the fibres of adjacent 

 plates passing in opposite directions and varying in every layer; so that the fibres of one layer 

 are directed across those of another, like the limbs of the letter X. This laminar arrangement 

 belongs to about the outer half of each disk. The pulpy substance presents no concentric arrange- 

 ment, and consists of a fine fibrous matrix, containing angular cells, united to form a reticular 

 structure. J. Bland Sutton 1 calls attention to the fact that in the human fetus a transverse 

 ligamentous band crosses the dorsal aspect of the inter.vertebral disk and is continuous with the 

 interosseous ligaments of the heads of the ribs; and also that a fetal ligamentous band exists in 

 the ventral surface of the intervertebral disk which, after development, becomes the middle 

 fasciculus of the stellate ligament. These bands are named by Sutton the posterior conjugal 

 ligaments and the anterior conjugal ligaments. 



Interneural articulations include the ligaments of the laminae; articular pro- 

 cesses, spinous processes, and transverse processes. 



2. LIGAMENTS CONNECTING THE LAMINAE. 

 Ligamenta Subflava. 



The ligamenta subflava (ligamenta iutercruralia) (Figs. 222 and 223) are inter- 

 posed between the laminae of the vertebra?, from the axis to the sacrum. They 

 are most distinct when seen from the interior of the vertebral canal ; when viewed 

 from the outer surface they ap- 

 pear short, being overlapped by 

 the laminae. Each ligamentum 

 .suhflavum consists of two lateral 

 portions, which commence on 

 each side at the root of either 

 articular process, and pass back- 

 ward to the point where the 

 laminae converge to form the 

 spinous process, where their mar- 

 gins are in contact and to a 

 certain extent united; slight in- 

 tervals being left for the passage 

 of small vessels. These ligaments 

 consist of yellow elastic tissue, 

 the fibres of which, almost per- 

 pe.idicular in direction, are at- 

 tached to the anterior surface of 

 the laminae above, some distance 

 from its inferior margin, and to 

 the posterior surface, as well as 

 to the margin of the lamina 

 below. In the cervical region 

 they are thin in texture, but very 

 broad and long; they become 

 thicker in the thoracic region, 

 and in the lumbar acquire very 



Considerable thickness. TheiV FIG. 223. Vertebral arches with ligamenta flava. 



1 Ligaments: Their Nature and Morphology, 1887. 



