123 



Action of these joints is elevation and depression of ribs on 

 a transverse axis through the head of a rib and its articular 

 process i. e., lengthwise through its neck; there are also ever- 

 sion and inversion of ribs on an axis connecting their sternal 

 and vertebral ends. No movement on a vertical axis. 



THE ARTICULATIONS OF THE COSTAL CARTILAGES 

 WITH THE STERNUM (COSTOSTERNAL) 



They are anterior chondrosternal, posterior chondrosternal, 

 capsular, and an intraarticular chondrosternal. The anterior 

 one is a broad radiating band with the superior, middle, and 

 inferior fasciculi. They intermingle with those of the opposite 

 side and with the origin of the pectoralis major, forming a 

 membrane over the sternum membrana sterni. The posterior 

 chondrosternal ligaments are less distinct, and are composed 

 of radiating fibers blending with the periosteum. The capsular 

 ligaments are very thin, and connected with the anterior and 

 posterior ones. The intraarticular chondrosternal ligament 

 is found between the second costal cartilage and the sternum, 

 attached by one extremity to the cartilage of the second rib, 

 and by the other to the cartilage which connects the first 

 and second portions of the sternum. Sometimes the third 

 rib has the same ligament situated as above, only located 

 between the second and third pieces of the sternum. This 

 joint has two synovial membranes. 



Synovial Membranes. The first cartilage has none, and the 

 sixth and seventh usually have none; the third, fourth, and 

 fifth have one; the second has two and an interarticular cartilage 

 resembling a vertebral articulation. In old age most of these 

 articulations disappear. 



From the sixth and seventh cartilages chondroxiphoid (costo- 

 xiphoid) ligaments pass down and into the ensiform, strengthen- 

 ing the sheath of the rectus and limiting the aponeurosis of 

 the external oblique. 



THE INTERCOSTAL ARTICULATIONS (INTERCHONDRAL) 



There are external and internal intercostal ligaments. The 

 former, ligamenta intercostalia externa, lie in the nine or 

 ten upper spaces between the anterior end of the external 



