OF THE RIBS WITH THE VERTEBRA. 



235 



the head of each rib with the sides of the bodies of two vertebrae and the interver- 

 tebral disk between them. It consists of three flat bundles of ligamentous fibres, 

 which are attached to the anterior part of the head of the rib, just beyond the 

 articular surface. The superior fibres pass upward to be connected with the body 

 of the vertebra above ; the inferior one descends to the body of the vertebra 

 below ; and the middle one, the smallest and least distinct, passes horizontally 

 inward, to be attached to the intervertebral substance. 



Relations. In front, with the thoracic ganglia of the sympathetic, the pleura, 

 and, on the right side, with the vena azygos major; behind, with the interarticular 

 ligament and synovial membranes. 



In the first rib, which articulates with a single vertebra, this ligament does 

 not present a distinct division into three fasciculi ; its fibres, however, radiate, 

 and are attached to the body of the last cervical vertebra, as well as to the body of 

 the vertebra with which the rib articulates. In the tenth, eleventh, and twelfth 

 ribs also, which likewise articulate with a single vertebra, the division does not 

 exist ; but the fibres of the ligament in each case radiate and are connected with 

 the vertebra above, as well as that with which the ribs articulate. 



The Capsular Ligament is a thin and loose ligamentous bag, which surrounds 

 the joint between the head of the rib and the articular cavity formed by the 

 intervertebral disk and the 

 adjacent vertebra. It is 

 very thin, firmly connected 

 with the anterior ligament, 

 and most distinct at the 

 upper and lower parts of 

 the articulation. Behind, 

 some of its fibres pass 

 through the intervertebral 

 foramen to the back of the 

 intervertebral disk. This 

 is the analogue of the liga- 

 mentum conjugate of some 

 mammals, which unites the 

 heads of opposite ribs across 

 the back of the interverte- 

 bral disk. 



The Interarticular Liga- 

 ment is situated in the 

 interior of the joint. It 

 consists of a short band of 

 fibres, flattened from above 

 downward, attached by one 

 extremity to the sharp 

 crest which separates the 

 two articular facets on the head of the rib, and by the other to the intervertebral 

 disk. It divides the joint into two cavities, which have no communication with 

 each other. In the first, tenth, eleventh, and twelfth ribs the interarticular liga- 

 ment does not exist ; consequently there is but one synovial membrane. 



The Synovial Membrane. There are two synovial membranes in each of the 

 articulations in which there is an interarticular ligament, one on each side of this 

 structure. 



2. ARTICULATIONS OF THE NECKS AND TUBERCLES OF THE RIBS AVITH 



THE TRANSVERSE PROCESSES (Fig. 161). 



The articular portion of the tubercle of the rib and adjacent transverse process 

 form an arthrodial joint. 



In the eleventh and twelfth ribs this articulation is wanting. 



ity. 



Lower synovial cavity. 



FIG. 160. Costo-vertebral and costo-transverse articulations. Ante- 

 rior view. 



