14 Anatomy Applied to Medicine and Surgery. 



moves on the interarticular fibre-cartilage, but, in adduc- 

 tion and abduction, the clavicle and cartilage together 

 move on the sternum. The joint, therefore, acts as a 

 pivot for the whole of the supporting arch of the shoulder. 

 Elevation is due to the trapezius, the sterno^mastoid and 

 the levator anguli scapulae ; depression, to gravity, assist- 

 ed by the subclavius, pectoralis major, latissirmis dorsi, 

 pectoralis minor and the lower fibres of the trapezius ; ab- 

 duction to the rhomboidei, levator anguli scapulae, middle 

 fibres of the trapezius, and indirectly, to the latissimus 

 dorsi ; adduction to the pectoralis minor, the serratus mag- 

 nus and the pectoralis major. 



Application. When the sterno-clavicular joint is 

 inflamed, the swelling is early appreciated in front, partly 

 because of the superficial situation of the joint, and partly 

 from the fact that the anterior ligament is more lax than 

 the other portions of the capsule. It is said that this joint, 

 more than any other, is affected in pyaemia, possibly be- 

 cause every movement of the shoulder disturbs it, with the 

 result, that there would be greater chance of trie arrest of 

 pus organisms in it. A patient suffering from inflamma- 

 tion of the sterno-clavicular articulation will lower the 

 point of the shoulder, as much as possible, since such de- 

 pression of the clavicle would increase the capacity of the 

 joint by separating the sides of the V and thus lessen the 

 pressure of the effusion on the sensitive nerves of the in- 

 flamed synovial membrane. In inflammation of this joint, 

 the muscles controlling the movements of the scapula and 

 clavicle will hold these bones as rigidly as possible, since 

 any movement of them would affect the joint and thus 

 cause pain. In this connection it is interesting to note 

 that both the joint itself and the principal muscles control- 

 ling it are supplied by the same nerves. The trapezius, 

 for instance, is supplied by the fourth cervical nerve, but 



