7H 



DISSECTION OF THE NECK. 



Fibro- 

 cartilage ; 



attach- 

 ments. 



Two 



syuovial 



sacs. 



Motion in 



four 



directions. 



cartilage of the first rib lo a rough mark on the under surface of 

 the clavicle near the sternal end. In front of the ligament is the 

 origin of the subelavius muscle. Sometimes the ligament is hollow, 

 and contains a synovial bursa. 



The interarticular fibro-cartilage (fig. 256, 7 ) will come into view 

 by cutting the ligaments before described, and raising the clavicle. 

 It is ovalish in form and flattened, and is thicker at the circumference 

 than in the centre. Its upper margin is firmly united to the inner 

 end of the clavicle ; and below, it is similarly fixed to the cartilage 

 of the first rib. At its circumference it unites with the capsule of 

 the joint. The fibro-cartilage is of considerable strength, and 

 prevents the clavicle being displaced upwards or inwards. 



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

 of the fibro-cartilage. The external one is prolonged outwards for a 

 short distance below, between the clavicle and the cartilage of the 

 first rib. 



Movements. The clavicle can be moved upwards and downwards 

 and forwards and backwards ; but the extent of movement in each 

 direction is very limited, in consequence of the shortness of the 

 ligaments surrounding the articulation : the forward and upward 

 movements are freer than the opposite. In the upward and down- 

 ward movements, the clavicle glides on the interarticular fibro- 

 cartilage ; and when the shoulder is depressed, the inner end of the 

 bone is raised, while elevation of the shoulder is accompanied by a 

 sinking of the inner end of the clavicle. In the forward and 

 backward movements, the fibro-cartilage glides in the same direction 

 over the sternal articular surface. Dislocation may take place in 

 any direction, except downwards ; but it is of rare occurrence owing 

 to the strength of the ligament*. 



