THE ARTICULATIONS OF THE RIBS. 159 



The iiiterarticular ligament is a thin and short band of fibres, which passes 

 transversely from the ridge separating the two articular surfaces on the head of the rib 

 to the intervertebral disc, and divides the articulation into two parts, each lined 

 by a separate synovial membrane. The ligament does not exist in the articulations 

 of the first, eleventh, or twelfth ribs, as these ribs are each attached to only one 

 vertebral body by a single synovial joint. 



Conjugal lig-ament. In many mammals there is a band known as the lig amentum conju- 

 gale eostarum. uniting- the heads of opposite ribs across the back of the intervertebral disc. This 

 ligament is represented in man by fibres passing 1 from the hinder part of the-neck of the rib 

 through the intervertebral foramen to the back of the intervertebral disc and the correspond- 

 ing process of the posterior common ligament of the vertebrae (lig. conjugate colli costce 

 Luschka). According to Sutton the conjugal ligament is distinct in the human foetus from 

 the seventh month, and the interarticular ligament is derived from its outer end. 



The COSTO-TRANSVERSE ARTICULATION unites the tuberosity of the rib to the 

 corresponding transverse process by a simple synovial joint, and ligaments pass 

 from the tuberosity and neck of the rib to the transverse processes of its proper 

 vertebra and of the vertebra above. 



The posterior costo-trans verse ligament is a distinct band extending out- 

 wards from the posterior part of the summit of the transverse process to the rough 



Fig. 185. HORIZONTAL SECTION OP A DORSAL 



VERTEBRA, WITH THE ADJACENT PORTIONS 



OF TWO RIBS. (R. Quain.) f 



1, rib ; 2, transverse process; 3, anterior costo- 

 central ligament ; 5, posterior costo-transverse 

 ligament ; 6, middle costo-transverse ligament. 



external part of the tuberosity of the 

 rib. 



The middle or interosseous 

 costo-transverse ligament consists 

 of a series of short parallel fibres, which 



unite the neck of the rib to the anterior surface of the contiguous transverse process. 

 These fibres are seen on removing by horizontal section a portion of the rib and 

 transverse process, and forcibly drawing the one from the other. 



The superior costo-transverse ligaments are two in number, anterior and 

 posterior. The anterior is a flattened band composed of fibres which pass from a 

 ridge on the upper border of the neck of the rib upwards and outwards to the lower 

 margin of the transverse process next above it. Its internal margin is thickened 

 and free ; externally it is continued into the posterior intercostal aponeurosis, which 

 occupies the hinder portion of the intercostal space. The posterior is a smaller and 

 less regular fasciculus extending from the neck of the rib upwards and inwards to the 

 base of the transverse process and the outer side of the lower articular process of the 

 vertebra above. These ligaments are wanting to the first rib. 



A third ascending band, external to the last, is sometimes present, running from the outer 

 part of the tuberosity of the rib to the tip of the transverse process above. 



There are no synovial joints between the lowest two ribs and the transverse 

 processes, and the posterior and middle costo-transverse ligaments are represented 

 by a single band. 



The CHONDRO-STERNAL ARTICULATIONS, situated between the inner extremities 

 of the cartilages of the sternal ribs and the corresponding fossas in the margins of 

 the sternum, are, with the exception of the first, small synovial joints, surrounded 



