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THE ARTICULATIONS. 



Article III. — Articulations of the Thorax. 



These are also divided into extrinsic and intrinsic. The first, named 

 costo-vertebral, unite the ribs to the spine. The second join the diiferent 

 pieces of the thorax together ; they comprise : 1, The chondro-sternal 

 articulations ; 2, Chondro-oostal articulations ; 3, The s^rticulations of the 

 costal cartilages with each other ; 4, The sternal articiilation peculiar to 

 the larger Euminants and the Pig. All these joints will be first studied in a 

 particular manner, then examined ia a general way as to their movements. 



1. Articulations of the Bibs with the Vertebral Column, or Costo-vertebral 



Articulations. 



Each rib responds to the vertebral column by two points — its head and 

 its tuberosity. The first is received into one of the intervertebral cavities 

 hollowed out on the sides of the spine, and is therefore in contact with two 

 dorsal vertebrte ; the second rests against the transverse process of the 

 posterior vertebra. Prom this arrangement arises two particular articulations 

 belonging to the artbrodial class, which are named costo-vertebral and costo- 

 transverse. 



Costo-vertebral Articulations. — Articular surfaces. — Pertaining to 

 the rib, we have the two convex facets of the head, separated from each 

 other by a groove of insertion and covered by a thin layer of cartilage. 

 On the vertebrae, the concave facets which by their union form the inter- 

 vertebral cavity ; these facets are also covered with cartilage, and separated, 

 at the bottom of the cavity by the corresponding intervertebral disc. 



Mode of union. — 1. An interarticular ligament (Pigs. 83, 2 ; 84, 1), im- 

 planted in the groove of insertion of the head of the rib, and attached to 



Fig. 83. 



ARTICULATIONS OF THE RIBS WITH THE VER- 

 TEBRAE, AND OP THESE WITH EACH OTHER 

 (UPPER PLANE). 



1, Spinal canal, upper face, showing the 

 common superior ligament; 2, Interar- 

 ticular costo-Tertebral ligament ; 3, Inter- 

 osseous costo-transrerse ligament ; 4, Pos- 

 terior costo-transverse ligament. 



ARTICULATIONS OF THE RIBS WITH THE VER- 

 TEBB/E, AND OF THESE WITH EACH OTHER 

 (iNPERrOR PLANE). 



1, Interarticular costo-vertebral ligament; 

 2, 3, 4, Fasciculi of the stellate, or in- 

 ferior costo-vertebral ligament ; 5, Common 

 inferior vertebral ligament. 



the superior border of the intervertebral disc, which it encircles upwards 

 and inwards, to unite on the median line with the ligament of the opposite 

 side. 2. An inferior periphera i ligament (Fig. 84, 2, 3, 4), flat above and 

 below, thin and radiating ("whence it is often named the stellate ligament), 

 formed of three fasciculi which are fixed in common on the inferior face of 



