160 



THE ARTICULATIONS OF THE TRUNK AND HEAD. 



by short capsules, which are most developed in front and behind, and thus form 

 anterior and posterior ligaments. The fibres of the anterior ligament radiate from 

 the extremity of the cartilage to the anterior surface of the sternum, where they 

 interlace with those of the opposite side, and are blended with the tendinous fibres 

 of origin of the pectoralis major muscle ; the fibres of the posterior ligament are 

 similarly disposed, but are not so thick or numerous. In the second articulation 

 the synovial cavity is divided into two by a short inter articular ligament, passing 

 horizontally between the end of the costal cartilage and the fibro-cartilaginous layer 

 uniting the manubrium to the body of the sternum ; and similar divisions some- 

 times exist in the succeeding joints. The synovial cavity is frequently wanting 



Fig. 186. ARTICULATIONS OP THE STERNUM, CLA- 

 VICLE, AND RIBS, SEEN FROM BEFORE. (Allen 



Thomson, after Arnold.) 



On the right side the anterior ligaments are 

 shown ; on the left side, the front parts of the cla- 

 vicle, sternum and costal cartilages have been re- 

 moved so as to display the articular cavities. 1 

 to 10, the anterior extremities of the ribs from the 

 first to the tenth inclusive, on the right side ; 1' to 

 10', the costal cartilages of the left side from the 

 first to the tenth ; at 1', the direct union of the 

 first costal cartilage with the sternum is shown ; at 

 the sternal ends of the cartilages marked 2' to 7', 

 the small synovial cavities are opened ; between the 

 costal cartilages on the right side the anterior 

 intercostal aponeuroses are shown stretching over 

 the intercostal spaces ; and on the left side, by a 

 section, small synovial cavities are shown between 

 the adjacent edges of the costal cartilages from the 

 5th to the 9th ; on the front of the right half of the 

 sternum the radiating anterior chondro-sternal liga- 

 ments are shown ; 11, ensiform process ; 12, 12', 

 interclavicular ligament ; and below 12, the anterior 

 sterno-clavicular ligament ; below 12', the sterno- 

 clavicular articulation is opened, showing the inter- 

 articular fibro-cartilage and double synovial cavity ; 

 13, the costo- clavicular or rhomboid ligament. 



in the articulations of the sixth and seventh 

 cartilages. The cartilage of the first rib 

 is almost always directly united to the 

 sternum. 



A variable fasciculus of fibres connect- 

 ing the cartilage of the seventh rib and 



sometimes likewise that of the sixth, with the xiphoid cartilage, is called the costo- 

 xiphoid. ligament. 



The IXTERCHONDRAL ARTICULATIONS are synovial joints formed by the processes 

 on the adjacent margins of some of the costal cartilages, viz., from the fifth (sometimes 

 the sixth) to the eighth or ninth, surrounded by short capsules. The joints are 

 strengthened anteriorly by oblique ligamentous fibres, derived from the anterior 

 intercostal aponeuroses which occupy the fore parts of the intercostal spaces. 



Connection of the ribs with the cartilages. The external extremities 

 of the cartilages are fixed into the oval depressions on the ends of the ribs, and the 

 union receives support from the periosteum. 



A synovial joint is occasionally formed between the first rib and its cartilage, or in the 

 outer part of the cartilage when ossification around the latter is far advanced. (Luschka. 

 " Die anomalen Articulationen des ersten Bippenpaares," Wiener Sitzungsber., 1860 ; W. A. Lane, 

 Guy's Hosp. Reports, xliii.) 



