ARTICULATIONS AND LIGAMENTS. 115 



bodies of the two adjacent vertebrae, except the first, tenth, 

 eleventh, and twelfth ribs, which have each but a single joint. 



Anterior Costo-vertebral, or Stellate Ligament. Origin, 

 head of the rib ; insertion, into body of vertebra above and below, 

 and interarticular cartilage between. 



Interarticular costo-vertebral is within the capsular liga- 

 ment, from the crest on the head of the rib to the intervertebral 

 substance. 



Capsular ligament surrounds the articular surfaces. 



Costo-transverse articulations are united by three ligaments 

 anterior, middle, and posterior costo-transverse ligaments 

 extending between the tubercles of the ribs to the transverse proc- 

 ess below. Arteries, the intercostals ; nerves, anterior branches 

 of spinal. 



COSTO-STERNAL ARTICULATIONS. These are connected by 

 arthrodia excepting the first, which is a synarthrodia. 



Anterior chondro-sternal ligaments connect the chondral 

 and sternal surface in front; 



Posterior chondro-sternal connect them behind. 



Capsular ligaments surround all, and synovial membranes 

 are present in all but the first, while the second has an inter- 

 articular cartilage interposed. 



The chondro-xiphoid ligament connects the cartilage of the 

 seventh, and sometimes the sixth rib with the xiphoid appendix. 



Interchondral and Costo- chondral Articulations. The ribs 

 are connected with their cartilages by the periosteum covering 

 them. The cartilages of the sixth, seventh, and eighth ribs, and 

 sometimes the fifth and ninth, are connected by anterior and 

 posterior inter- chondral ligaments, held together by capsular 

 ligaments and lined with synovial membrane. 



LIGAMENTS OF STERNUM. The first and second portions of 

 the sternum are articulated by an amphiarthrodial joint, some- 

 times a diarthrodial joint, connected by the anterior intersternal 

 and posterior intersternal ligaments, and lined with synovial 

 membrane. 



The third portion, or ensiform cartilage, is united to the 

 gladiolus by a synarthrodial joint. 



THE THORAX. 



The thorax is a conical osteo-cartilaginous framework, 

 formed by the dorsal vertebra behind, the ribs, intercostal mus- 

 cles, and costal cartilages laterally, and the sternum in front. 



The apex, or superior opcnimj. is bounded behind by the 

 first dorsal vertebra, laterally by the first rib, and in front by the 

 upper border of the sternum. 



