190 ARTICULATIONS. 



turned towards the corresponding surfaces of the vertebrae, and consist of alternate 

 plates of fibrous tissue and fibro-cartilage. These plates are not quite vertical in 

 their direction, those near the circumference being curved outwards and closely 

 approximated, whilst 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 downwards ; the fibres of an 

 adjacent plate have an exactly opposite arrangement, varying in their direction in 

 every layer ; whilst in some few they are horizontal. This laminar arrangement 

 belongs to about the outer half of each disk, the central part being occupied by a 

 soft, pulpy, highly elastic substance, of a yellowish color, which rises up con- 

 siderably above the surrounding level, when the disk is divided horizontally. 

 This substance presents no concentric arrangement, and consists of white fibrous 

 tissue, having interspersed cells of variable shape and size. The pulpy matter, 

 which is especially well developed in the lumbar region, is separated from imme- 

 diate contact with the vertebrae, by the interposition of thin plates of cartilage. 



2. LIGAMENTS CONNECTING THE LAMINAE. 

 Ligamenta Subflava. 



The Ligamenta Subflava are interposed between the laminae of the vertebrae, 

 from the axis to the sacrum. They are most distinct when seen from the interior 

 of the spinal canal ; when viewed from the outer surface, they appear short, being 

 overlapped by the laminae. Each ligament consists of two lateral portions, which 

 commence on each side at the root of either articular process, and pass backwards 

 to the point where the laminae converge to form the spinous process, where their 

 margins are thickest, and separated by a slight interval, filled up with areolar 

 tissue. These ligaments consist of yellow elastic tissue, the fibres of which, almost 

 perpendicular in direction, are attached to the anterior surface of the margin of the 

 lamina above, 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 dorsal region, and in the lumbar acquire very consi- 

 derable thickness. Their highly elastic property serves to preserve the upright 

 posture, and to counteract the efforts of the flexor muscles of the spine. These 

 ligaments do not exist between the occiput and atlas, or between the atlas and axis. 



3. LIGAMENTS CONNECTING THE AKTICULAR PEG CESS. 



Capsular. 



The Capsular Ligaments are thin and loose ligamentous sacs, attached to the 

 contiguous margins of the articulating processes of each vertebra, through the 

 greater part of their circumference, and completed internally by the ligamenta 

 subflava. They are longer and more loose in the cervical than in the dorsal or 

 lumbar regions. The capsular ligaments are lined on their inner surface by 

 synovial membrane. 



4. LIGAMENTS CONNECTING THE SPINOUS PROCESSES. 



Inter-spinous. Supra-spinous. 



The Inter-spinous Ligaments, thin and membranous, are interposed between the 

 spinous processes in the dorsal and lumbar regions. Each ligament extends from 

 the root to near the summit of each spinous process, and connects together their 

 adjacent margins. They are narrow and elongated in the dorsal region, broader, 

 quadrilateral in form, and thicker in the lumbar region. 



The Supra-spinous Ligament is a strong fibrous cord, which connects together 

 the apices of the spinous processes from the seventh cervical to the spine of the 

 sacrum. It is thicker and broader in the lumbar than in the dorsal region, and 

 intimately blended, in both situations, with the neighboring aponeuroses. The 



