DISSECTION OF THE DOG 227 



bone, in order that the ligaments connected with these parts of the 

 skeleton may be examined. 



The bodies of adjacent vertebrae are connected by discs of fibro-cartilage 

 (fibrocartilagines intervertebralcs). If two vertebra? be separated from each 

 other, it wall readily be seen that the connecting cartilage is composed of a 

 peripheral fibrous portion (annulus fibrosus) and a much softer central part 

 (nucleus pulposus). Assisting in the firm union of the vertebra? are two 

 longitudinal bands. The ventral longitudinal ligament (lig. longitudinale 

 ventrale) is attached along the ventral aspect of the vertebral bodies from the 

 sacrum to about the fifth thoracic vertebra, where it materially diminishes 

 in volume. The dorsal ligament (lig. longitudinale dorsale) is more sharply 

 defined. Running along the ventral wall of the vertebral canal from the 

 sacrum to the dens of the epistropheus, it has the form of a band of 

 unequal width. At each intervertebral fibro-cartilage the ligament widens 

 somewhat, to become narrow again on a level with the vertebral body. 



Yellow ligaments (ligamenta flava) bridge the narrow gap between neigh- 

 bouring vertebral arches. In the thoracic region these ligaments are narrow, 

 but are considerably wider in the cervical region. The joint-cavities between 

 contiguous articular processes of the vertebra? are enclosed by joint-capsules 

 (capsular articulares) with the customary attachment around the articular 

 surfaces, and possessed of the usual synovial lining. 



Forming the bond of union between the vertebral spinous processes are 

 the supraspinal and interspinal ligaments. The supraspinal ligament (lig. 

 supraspinal) is a strong cord-like object attached to the summits of the pro- 

 cesses from the sacrum to about the first thoracic vertebra, where it is 

 continuous with the ligament of the nape. The interspinal ligaments (ligg. 

 interspinalia) fill the intervals between the spinous processes, and are confined 

 to the thoracic and lumbar regions. In the lumbar region intertransverse 

 ligaments (ligg. intertransversaria) connect the transverse processes. 



Articulatio atlanto- occipitalis. — The articulation between the atlas 

 and the condyles of the occipital bone has a cavity continuous with that 

 between the atlas and the epistropheus, and is enclosed by a joint-capsule 

 (capsula articularis) on each side. An extensive ventral atlanto- occipital 

 membrane (membrana atlanto-occipitalis ventralis), disposed on the ventral 

 side of the joint, closes in the interval between the atlas and the occipital 

 bone ; while a dorsal membrane (membrana atlanto-occipitalis dorsalis), also 

 extensive but rather stronger than the ventral membrane, bridges the 

 space on the dorsal aspect of the articulation. The union of the two bones 

 is finally effected by the presence of a lateral atlantal ligament (lig. laterale 

 atlantis) on each side. This is connected with the joint-capsule, and runs 

 from the edge of the atlas to the jugular process of the occipital bone. 



Q2 



