THORACIC ARTICULATIONS. 



133 



ridge on the head of one rib through the articulation, giving a 

 sHp to the intervertebral disc, and 

 is attached to the fellow rib on the 

 opposite side ; the head of the rib 

 is thus divided into two distinct 

 articulations, with cai^sidar liga- 

 ments and synovial sacs. Super- 

 iorly the anterior costo-transverse 

 unites the neck of the rib to the 

 infero-anterior part of the vertebral 

 transverse process, while the jws- 

 terior costo-transverse passes from 

 the supero-posterior part of the 

 tubercle to the lateral part of the 

 transverse process. One capsular 

 ligament unites the tubercle and 

 transverse process, enclosing a syno- 

 vial sac. 



Fin. 47. 



C'osto-vertebral articulation, right lateral 

 aspect, a, Anterior, and b, Posterior 

 costo-transverse ligaments ; c, Ligamen- 

 tum subflavum ; d, Interspinous, and 

 t', Supra-spisioiis ligaments 



Fig. 4S. 

 Costo-vertebral articulation. Neural canal opened from 

 above, and superior common ligament removed, a. Inter- 

 articular ligament ; b b, Branches joining the disc. 



CJiondro-costal Articulation. — This is a fixed joint between 

 the rib and its cartilage ; each rib is cupped on its lower 

 extremity, the convexity of the cartilage resting in it, and the 

 joint, a gomphosis, is clothed around with strong fibrous tissue. 



Costo-sternal Articulation. — This joint is formed by two 

 sternal segments and a true costal cartilage. The first cartilage, 

 however, articulates with the presternum only, and the last only 

 with the last sternal segment. The ligaments are the capsular 

 and the superior and inferior costo-sternal, which stretch from 

 the costal cartilages to the sternum aBbve and below, blending 

 with the capsular ligament. 



The asternal or false cartilages are united, each free extremity 

 becoming attached to the cartilage in front by a small elastic 

 ligament. The first asternal cartilage is very firmly attached to the 

 last sternal one ; a small ligament, the chondro-xiphoicl, is also 

 described, which connects the xiphoid and first asternal cartilages. 



