264 THE ARTICULATIONS OR JOINTS. 
The posterior costo-sternal ligament—also a part of the capsule—has attach- 
ments similar to the foregoing, but the arrangement of its fibres is not so powerful. 
The ligamentum costo-xiphoidea passes from the front of the upper part of the 
xiphoid cartilage, obliquely upwards and outwards to the front of the seventh, and 
sometimes to the front of the sixth costal cartilage. 
Within the capsules of these joints interarticular ligaments (ligg. sterno-costalia 
interarticularia, Fig. 207) may be found. Their disposition is somewhat uncertain, for 
cavity 
Clavicle 
Joint 
~Interclavicular 
Meniscus 
ligament 
‘Joint cavity 
_ Costo-clavicular or 
rhomboid ligament 
. Anterior sterno-clavicular 
ligament 
Joint capsule 
Joint cavity 
Interarticular ligament ~ 
Joint cavity 
_ Anterior chondro-sternal or 
radiate ligament 
Fic. 207.—STERNO-CLAVICULAR AND COSTO-STERNAL JOINTS. 
whereas, in the case of the second pair of cartilages, they invariably divide the joint 
cavity into two distinct compartments—an upper and a lower—such an arrange- 
ment is very uncertain in the other joints, and they occasionally, especially in the 
cases of the sixth and seventh cartilages, entirely obliterate the joint cavity. These 
igaments extend horizontally between the ends of the costal cartilages and the 
side of the sternum. 
Synovial membrane is found wherever a joint cavity is developed, and therefore 
there may be one or two synovial membranes, according to the presence or absence 
of a proper interarticular ligament. When the joint cavity is obliterated by the 
fibrous structure which represents the interarticular ligament, a synovial membrane 
is also absent. 
STERNAL ARTICULATIONS. 
Primarily the sternum consists of an elongated plate of hyaline cartilage, which 
becomes subdivided into segments by the process of ossification. 
The four segments of which the gladiolus is originally composed unite with ~ 
each other after the manner of typical synchondroses. 
Similarly the ensiform cartilage and the gladiolus ultimately become united. 
It is not usual to find the manubrio-gladiolar joint obliterated by the ossification of 
the two bony segments. Even in advanced life it remains open, and the joint par- 
takes of the nature of an amphiarthrosis (Fig. 207), although a joint cavity is not 
found under any circumstances in the plate of fibro - cartilage which intervenes 
between the manubrium and the gladiolus. 
The membrana sterni, to which reference has already been made, assists in 
strengthening the union between the different segments of the sternum. 
Movements of the Ribs and Sternum.—These movements may be considered either 
independently of, or as associated with, respiration. 
In the former condition the ribs move in connexion with flexion and extension of the 
yertebral column, being more or less depressed and approximated in the former, and elevated or 
is Gel a i mn el ee 
