Chap, xi.] THE CLAVICLE. 167 



in the callus formed. The three nerves that cross the 

 clavicle are branches of the third and fourth cervical 

 nerves, and it is well to note that pain over the collar 

 bone is sometimes a marked feature in disease of the 

 upper cervical spine. This symptom is then due 

 to irritation of these nerves at their points of exit 

 from the spinal canal. 



Beneath the clavicle the great vessels and the 

 great nerve-cords lie upon the tirst rib. The vein is 

 the most internal, and occupies the acute angle 

 between the collar bone and the first rib. It will be 

 seen that growths from the bone may readily press 

 upon these important structures, and that the vein, 

 from its position, as well as from the slighter resis- 

 tance that it offers, is likely to be the first to be 

 compressed. These structures have also been wounded 

 by fragments of bone in. fracture of the clavicle. Fortu- 

 nately, between the clavicle and these large nerves 

 and vessels the subclavius muscle is interposed. This 

 muscle is closely attached to the under surface of the 

 bone, is enveloped in a dense fascia, and forms one of 

 the chief protections to the vessels in cases of fracture. 

 This interposing pad of muscle is also of great service 

 in resection operations, as can be well understood. 

 Braune states that by pressing the clavicle against the 

 first rib in the dead body a stream of injection in the 

 thoracic duct can, in some cases, be entirely arrested. 

 Behind the clavicle the following structures may be 

 noted : The brachio-cephalic, subclavian, and external 

 jugular veins, the subclavian, suprascapular, and in- 

 ternal mammary arteries, the cords of the brachial 

 plexus, the phrenic nerve and nerve of Bell, the thoracic 

 duct, the omo-hyoicl, scalene, sterno-hyoid and sterno- 

 thyroid muscles, the apex of the lung. The sternal 

 end of the bone is not far removed from the innominate, 

 or left carotid artery, the vagus and recurrent nerves, 

 the trachea, and the oesophagus. 



