182 



THE ARTICULATIONS. 



vertebrae, constitutes a vast triangular and vertical septum, which itself results from 

 the apposition of the two laminae that lie back to back, and are united by 

 connective tissue ; they are bordered above by the two lateral lips of the cord. The 

 elastic fibres which enter into their composition are given off either from the 

 latter, or from the spinous processes of the second and third dorsal vertebrae ; 

 they are directed downwards or forwards, and reach the spinous processes of the 

 last six cervical vertebrae, into which they are inserted by so many digitations, 

 becoming confounded with the interspinous ligaments of the neck. The fibres 

 of the two last digitations are few in number, widely separated from one another, 

 and united by many anastomosing branches, which make them appear as a kind 

 of wide network. The lamina of the cervical ligament are in relation, outwardly, 

 with the superior branch of the ilio-spinal ligament, the intertransversalis colli 

 muscles, and the complexus muscle. 



(This important structure, which is, in reality, 

 the mechanical stay and support of the heavy head 

 and neck of quadrupeds, and is usually temied the 

 ligamentvm nucJm, is all but absent in Man, being 

 represented in him by a tliin narrow band — or rather 

 two thin planes of fibres, the ligamenta suhflava. It 

 is described by Leyh as if there were not two portions, 

 and that excellent anatomist does not appear to insist 

 suificiently on the difference between the dorso-nuchal 

 and the dorso-lumbar divisions. Percivall, who almost 

 entirely neglects the ligaments, also makes no distinc- 

 tion. The difference in structure, elasticity, and 

 situation, wairants the distinction made by Chauveau. 

 As already indicated, the function of this ligament — 

 and more particularly of its nuchal division — is to 

 maintain the head and neck in their natural position 

 during repose, and to allow the most extensive move- 

 ments at other times.) 



c. Interspinous Ugaments (Fig. 121, 3). — Fibrous 

 laminae fill the interspinous spaces, and are attached, 

 before and behind, to the opposite borders of the spinous 

 processes, which they unite. They are confounded 

 superiorly with the supra-spinous hgament, and are continued inferiorly by the 

 interlamellar ligaments — forming two lateral planes which are applied against each 

 other, hke the laminae of the cervical ligament, and covered outwardly by the inter- 

 transversalis colli muscles. 



In the region of the neck, the interspinous ligaments are yellow and elastic. 

 In the dorso-lumbar region, they are formed by fasciculi of white fibrous tissue, 

 loosely united to each other at their extremities, and directed very obliquely 

 backwards and downwards. In consequence of this disposition, and notwith- 

 standing their inextensibility, they permit the separation of the spinous processes. 

 Their lateral surfaces are divided by a layer of grey elastic fibres, which cross hke 

 an X the direction of the preceding fasciculi. Very abundant in the anterior 

 moiety of the dorsal region, these fibres operate, by their proper elasticity, in 

 bringing the spinous processes towards each other. 



d. Interlamellar, or interannular ligaments. — Situated, as their name indicates, 

 between the vertebral laminae, and divided into two lateral moieties, these 



INTERVERTEBRAL ARTICULA- 

 TIONS. 



A, B, C, Bodies of three dorsal 

 ■vertebrse divided longitudi- 

 nally ami vertically to show 

 (1, i) a section of the inter- 

 vertebral discs ; 2, supra- 

 spinous dorso-lumbar liga- 

 ment ; 3, interspinous liga- 

 ment ; 4, fibrous fascia, con- 

 stituting the proper capsule 

 of the articular processes in 

 the dorsal region. 



