Il6 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 185. — The tectorial membrane seen from behind. The posterior portion of the occipital bone and 

 the arches of the three upper cervical vertebras have been removed, as well as the cap- 

 sular ligaments of the right side (t$). 



Fig. 186. — The atlanto-odontoid articulation. The odontoid process (dens epistrophei) and the anterior 

 arch of the atlas have been cut (yV). 



Fig. 187. — The cruciate ligament after removal of the tectorial membrane. The articular capsules have 

 also been removed on the right side (x\). 



Fig. 188. — The alar ligaments after removal of the cruciate ligament. The articular capsules as in the 

 preceding figure (jjf). 



THE ARTICULATIONS OF THE RIBS WITH THE VERTEBRAL COLUMN AND WITH THE 



STERNUM. 



The posterior extremities of the ribs are connected with the thoracic vertebras by arthrodial 

 joints (Figs. 172, 176, and 178 to 180); their anterior extremities (Fig. 181) articulate with the 

 sternum or with each other by means of either arthrodial joints or synchondroses. The anterior 

 extremities of the two lowermost ribs are not attached to any portion of the skeleton. 



The ribs are connected to the vertebras by a double articulation. The head of each rib 

 articulates with the bodies of two adjacent vertebras (the exceptions are given upon page 26) and 

 the tubercles of the ribs, with the exception of the last two (see page 27), articulate with the 

 transverse processes. 



The articulations of the heads of the ribs, with the exception of the uppermost and the two 

 lowermost, are characterized by the fact that the intervertebral fibrocartilage between the two 

 vertebrae forming the articular cavities is continued, as the interarticular ligament (Fig. 178), 

 as far as the crest upon the head of the rib, and divides the articulation into two compartments. 

 The weak articular capsules are reinforced by the radiate (stellate) ligaments (Figs. 172 and 180), 

 which arise from the head of the rib and radiate to the lateral surfaces of the bodies of the 

 vertebras forming the articulation. 



The costo-transverse articulations have capacious capsules and are characterized by possess- 

 ing quite a number of reinforcing or check ligaments. The posterior surface of the capsule is 

 reinforced by a short tense ligament, the ligament 0} the costal tubercle (posterior costo-transverse 

 ligament) (Fig. 179), which is approximately quadrangular and composed of parallel fibers, and 

 extends outward and slightly upward from the tip of the transverse process to the posterior sur- 

 face of the neck of the articulating rib. 



The ligament of the neck (middle costo-transverse or interosseous ligament) (Fig. 178) almost 

 completely fills the space between the neck of the rib and the transverse process of the thoracic 

 vertebra. It is horizontal and passes from the anterior surface of the transverse process of the 

 vertebra to the posterior surface of the neck of the rib. The costo-transverse (superior costo- 

 transverse) ligaments run between the posterior extremities of the ribs and the transverse proc- 

 esses, and each may be regarded as consisting of an anterior and a posterior costo-transverse liga- 

 ment, both of which pursue a similar course from the neck of the rib to the transverse process 

 of the overlying vertebra. The anterior ligament (Figs. 179 and 180) is tolerably strong and 

 approximately rhomboid in shape; it passes from the lower margin of the transverse process 



