STERNO-CLAVICULAR JOINT. 



171 



line, but dip into the hollow between the collar bones, and are connected 

 with the upper piece of the sternum. 



The costo-clavicular ligament (fig. 51, 2 ) is a short strong band of ob- 

 lique fibres between the first rib and the clavicle. Inferiorly it is fixed to 

 the upper surface of the cartilage of the first rib, and superiorly to a tuber- 

 cle on the under surface of the clavicle near the sternal end. The sub- 

 clavius muscle is in front of the ligament. 



Sometimes the clavicle touches the rib, and is provided with an articular 

 surface and a synovial membrane. 



The inter articular fibro-cartilaye (fig. 51, 7 ) will come into view by 

 cutting the ligaments before described, and raising the clavicle. It is 

 ovalish in form and flattened, but is thicker at the circumference than the 

 centre. By its upper margin and surface the cartilage is united to the 

 head of the clavicle which is imbedded in it; and by the opposite surface 

 and margin it is inserted into the cartilage of the first rib. At its cir- 

 cumference it unites with the capsule of the joint. Sometimes there is an 

 aperture in the centre of the fibro-cartilage. 



Two synovial sacs are present in the articulation, one on each side of 

 the fibro-cartilage. The sac in contact with the sternum is looser than 

 that touching the clavicle. 



Movement. The inner end of the clavicle can be moved up and down, 

 and forwards and backwards, and the direction it takes is the opposite to 





LlOAMENTS OP THE INNER END OP THE CLAVICLE, AND OP THE CARTILAGE OF THE SECOND BlB. 



1. Capsule. 4. Ligaments of the second rib with the sternum. 



2. Costo-clavicnlar ligament. 6. Interarticular fibre-cartilage of second rib. 



3. Interclavicular ligament. 7. Interarticular fibro-cartila^e of the clavicle. 



that of the shoulder : thus when the limb is depressed the sternal end of 

 the clavicle is raised ; and so on in the other movements. The extent of 

 each movement is but limited, though those forwards and upwards are the 

 freest ; and dislocation may ensue in any direction except downwards, 

 from force applied to the limb. 



