ARTICULATIONS OF THE THORAX. 



191 



intervertebral disc, Avhich it encii-cles upwards and inwards, to unite on the median 

 line with the ligament of the opposite side. 2. An inferior peripheral ligament 

 (Fig. 127, 2, 3, 4), flat above and below, thin and radiating (whence it is often 

 named the stellate ligament), formed of three fasciculi, wliich are fixed in common 

 on the inferior face of the head of the rib, and in diverging are carried over the 

 bodies of the two vertebrte and the intervertebral disc. Lmed above by the 

 synovial membranes, this ligament is covered below by the pleura. (Leyh includes 

 a capsular ligament for the head of the rib, and another for the costal tuberosity. 

 He probably considered the synovial membrane of these articulations as such.) 



Synovial membranes. — These are two in number — an anterior and posterior, 

 lying against each other, and separated in part by the interarticular ligament 

 they cover. Supported below by the stellate ligament, above they are directly in 

 contact with the levatores costarum muscles, and with vessels and nerves. 



CosTO-TRANSVERSE ARTICULATIONS. Avticular surfttces. — In the rib, the 



Fig. 127. 



Fig. 126. 



articulations of the ribs with the ver- 

 tebra, and of these with each other 

 (upper plane). 



1, Spinal canal, upper face, showing the common 

 superior ligament; 2, interarticular costo- 

 vertebral ligament ; 3, interosseous costo- 

 transverse ligament ; 4, posterior costo-trans- 

 verse ligament. 



ARTICULATIONS OF THE RIBS WITH THE 

 VERTEBRA, AND OF THESE WITH EACH 

 OTHER (INFERIOR PLANE). 



1, Interarticular costo-vertebral liga- 

 ment ; 2, 3, 4, fasciculi of the stellate, 

 or inferior costo-vertebral ligament; 5, 

 common inferior vertebral ligament. 



diarthrodial facet cut on the tuberosity. In the vertebra, the analogous facet on 

 the outside of the transveree process. 



Mode of union. Two ligaments bind this articulation : 1. The posterior costo- 

 transverse ligament (Fig. 126, 4), a white fibrous band attached by its extremities 

 behind the transverse process and the costal tuberosity, lined by synovial mem- 

 brane, and covered by the transverse insertions of several spinal muscles. 2. The 

 anterior costo-transverse., or interosseous ligament (Fig. 126, 3), a fasciculus of 

 short, thick, white fibres, fixed on the anterior surface of the transverse process 

 near its base, and in the rugged excavation on the neck of the rib. This liga- 

 ment is invested, posteriorly, by the synovial membrane, and covered in front by 

 pads of adipose tissue which separate it from the costo-vertebral articulation. 



Synovial membrane. — This is a small particular capsule, kept apart from the 

 posterior synovial membrane of the costo-vertebral articulation by the costo-trans- 

 verse interosseous ligament. 



Characters peculiar to some Costo-vertebral Articulations. — 1. 

 The first, and sometimes the second, costo-vertebral articulation has no inter- 

 osseous ligament, and only exhibits one synovial membrane. The intervertebral 



