ARTICULATIONS OF TEE SPINE. 179 



articular processes are easily dissected ; and on the dorsal region portions, the interspinous, 

 Bupra-spinous, interlamellar, and common inferior ligaments, can be examined. On those 

 portions from the lumbar region, in a horizontal section through the spinal canal, the inferior 

 face of the interlamellar ligaments and the common superior vertebral ligament will be seen ; 

 while in those from the dorsal region, a good idea will be derived of the common inferior 

 vertebral ligament. The intervertebral ligaments can be studied in vertical and horizontal 

 eections of the bodies of the vertebrae from any region. 



A second subject, which should be fixed in the third position (see Preparation of the 

 Muscles), is necessary for the dissection of the supra-spinous, dorso-lumbar, and cervical 

 ligament. This may be eflPected by removing the muscles which occupy the vertical channels 

 above the cervical vertebrse (see Preparation of the Cervical Kegions). 



Intervertebral Articulations. 



The vertebrae articulate : 1. By their bodies. 2. By their spinal or annular 

 portion. There results from this union two kinds of articulation, which must be 

 studied separately, as they do not belong to the same class. It is well to mention, 

 however, that the general details into which this study leads us, apply only to 

 the articulations uniting the last six cervical vertebrae, all the dorsal and lumbar 

 vertebrae, and the first sacral vertebra. 



Union op the Vertebra by their Bodies. — The articulations forming 

 this union are so many amphiarthroses. 



Articular surfaces. — The vertebral bodies come into contact by the surfaces 

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

 represent, anteriorly, a real 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 surfaces tend to become effaced and more and more 

 plane, though they still preserve their convexity and concavity. 



Means 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 fihro-cartilages (Fig. 121, 1, 1). — These are circular or 

 elliptical discs, convex in front, concave behind, and soUdly 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 histo- 

 logical 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 Hke an X, and are attached by their extremities to the 

 articular surfaces. From this aiTangement results so intimate an adherence 

 between the vertebral bodies and their intermediate fibro-cartilages, that an 

 attempt to disunite them is more likely to cause a fracture of the former. The 

 fibro-cartilages, thicker in the cervical and lumber regions than in the dorsal, 

 respond by their circumference to the two common ligaments. Those which 

 separate the vertebrte of the back concur to form the intervertebral cavities, 

 intended for the reception of the heads of the ribs, and give attachment to the 

 interosseous costo-vertebral ligaments. 



h. Common superior vertebral ligament (Fig. 126, 1). — This ligament extends 

 from the axis to the sacrum, and is lodged in the spinal canal. It is a long 

 fibrous band cut on its borders into wide festoons. By its inferior face, it is 

 attached to the intervertebral discs, and the triangular imprints on the upper 

 faces of the bodies of the vertebrte. Its superior face is in contact with the dura 



