188 ARTICULATIONS. 



ABTICULATIONS OF THE TRUNK. 



These may be divided into the following groups, viz : 



I. Of the vertebral column. Y. Of the ribs with the vertebras. 



II. Of the atlas with the axis. VI. Of the cartilages of the ribs with 



III. Of the spine with the cranium. the sternum, and with each other 



1. Of the atlas with the occipital bone. VII. Of the sternum. 



2. Of the axis with the occipital bone. VIII. Of the pelvis with the spine. 



IV. Of the lower jaw. IX. Of the pelvis. 



I. ARTICULATIONS OF THE YEETEBRAL COLUMN. 



The different segments of the spine are connected together by ligaments, which 

 admit of the same arrangement as the vertebrae. They may be divided into five 

 sets. 1. Those connecting the bodies of the vertebras. 2. Those connecting the 

 laminae. 3. Those connecting the articular processes. 4. The ligaments con- 

 necting the spinous processes. 5. Those of the transverse processes. 



The articulation of the bodies of the vertebras with each other forms a series of 

 amphiarthrodial joints ; whilst those between the articular processes form a series 

 of arthrodial joints. 



1. THE LIGAMENTS OF THE BODIES. 



Anterior Common Ligament. Posterior Common Ligament. 



Intervertebral Substance. 



The Anterior Common Ligament (fig. 116) is a broad and strong band of liga- 

 mentous fibres, which extends along the front surface of the bodies of the vertebras, 

 from the axis to the sacrum. It is broader below than above, and thicker in the 

 dorsal than in the cervical or lumbar regions ; it is also somewhat thicker opposite 

 the front of the body of each vertebra, than opposite the intervertebral substance. 

 It is attached, above, to the body of the axis by a pointed process, which is con- 

 nected with the tendon of origin of the Longus colli muscle ; and extends down 

 as far as the upper bone of the sacrum. It consists of dense longitudinal fibres, 

 which are intimately adherent to the .intervertebral substance and prominent 

 margins of the vertebras, but less closely with the middle of the bodies. In the 

 latter situation the fibres are exceedingly thick, and serve to fill up the concavities 

 on their front surface, and to make the anterior surface of the spine more even, 

 This ligament is composed of several layers of fibres, which vary in length, 

 but are closely interlaced with each other. The most superficial or longest fibres 

 extend between four or five vertebras. A second subjacent set extend between 

 two or three vertebras; whilst a third set, the shortest and deepest, extend from 

 one vertebra to the next. At the sides of the bodies, this ligament consists of a 

 few short fibres, which pass from one vertebra to the next, separated from the 

 median portion by large oval apertures, for the passage of vessels. 



The Posterior Common Ligament is situated within the spinal canal, and 

 extends along the posterior surface of the bodies of the vertebras, from the body 

 of the axis above, where it is continuous with the occipito-axoid ligament,, to the 

 sacrum below. It is broader at the upper than at the lower part of the spine, 

 and thicker in the dorsal than in the cervical or lumbar regions. In the situation 

 of the intervertebral substance and contiguous margins of the vertebras, where 

 the ligament is more intimately adherent, it is broad, and presents a series of 

 dentations with intervening concave margins ; but it is narrow and thick over the 

 centre of the bodies, from which it is separated by the venae basis vertebrae. This 

 ligament is composed of smooth, shining, longitudinal fibres, denser and more com- 

 pact than those of the anterior ligament, and composed of a superficial layer 



