ARTICULATIONS OF THE SJPINM. 131 



cervical vertebrae, all the dorsal and lumbar vertebras, and the first sacral 

 vertebra. 



Union of the VERTEBRiE by their Bodies. — The articulations forming this 

 union are so many amphiarthroses. 



Articular surf aces. —The vertebral bodies come into contact by the 

 surfaces which terminate them before and behind. In the cervical region 

 these surfaces represent, anteriorly, a veritable head, posteriorly, a cotyloid 

 cavity which receives the head of the next vertebra. Beginning from the 

 first dorsal vertebra and passing on to the sacrum, these tend to become 

 efiaced and more and more plane, though they still preserve their convexity 

 and concavity. 



Modes of union.— 1, By fibro-cartilages interposed between the articular 

 surfaces ; 2, By a common superior vertebral ligament ; 3, By a common 

 inferior vertebral ligament. 



a. Intervertebral fibro-cartilages (Fig. 80, 1, 1). — These are circular or 

 elliptical discs, convex in front, concave behind, and solidly fixed by their 

 faces to the articular planes which they separate. The fibro-cartilaginous 

 substance composing them consists of concentric layers, which become denser 

 and closer to each other as they near the circumference ; they even disappear 

 towards the centre of the disc, where this substance becomes pulpy and 

 assumes the histological characters of pure cartilage. It may be remarked, 

 that each of these layers is made up of a collection of thick parallel filaments, 

 which cross with those of other layers like an X, and are attached by their 

 extremities to the articular surfaces. Prom this arrangement results so inti- 

 mate an adherence between the vertebral bodies and their intermediate fibro- 

 cartilages, that an attempt to disunite them is more likely to determine a 

 fracture of the former. The fibro-cartilages, thicker in the cervical and 

 lumbar regions than in the dorsal, respond by their circumference to the 

 two common ligaments. Those which separate the vertebrae of the back 

 concur to form the intervertebral cavities, uhich are destined for the reception 

 of the heads of the ribs, and give attachment to the interosseous costo- 

 vertebral ligaments. 



(Leyh designates the superficial fibres of the excentric layer of these 

 fibro-cartilages as intervertebral ligaments. Luschka has shown that the 

 •cartilages are in reality articular capsules.) 



b. Common superior vertebral ligament (Fig 83, 1). — This ligament 

 extends from the axis to the sacrum, and is lodged in the spinal canal ; it 

 represents a long fibrous band cut on its borders into wide festoons. (The 

 wide portions correspond to the discs.) 



By its inferior face, it is attached to the intervertebral discs and the 

 triangular imprints on the upper faces of the bodies of the vertebras. Its 

 superior face is in contact with the dura mater through the medium of an 

 abundant cellulo-adipose tissue. Its borders ^re margined by the intra- 

 verfebral venous sinuses (vence basium veriebrarium). 



c Common inferior vertebral ligament(Fig. 84, 5).— Situated under the spine, 

 this ligament is absent in the cervical and the anterior third of thedorsal region. 

 It only really begins about the sixth or eighth vertebra of the latter region, 

 and is prolonged in the form of a cord, at first narrow, then gradually 

 widening until it reaches the sacrum, on the inferior surface of which it 

 terminates by a decreasing expansion. From its commencement, it is 

 attached to the inferior crest of the bodies of the vertebrse and the interver- 

 tebral discs. By its inferior face, it responds to the posterior aorta. 



(Levh commences this ligament at the seventh cervical vertebra, and says 



