THE NECK 129 



simple exostosis of the costal element to a fully formed rib, 

 articulating, by complete joints, with the transverse process and 

 body of the seventh cervical vertebra. The ventral extremity of 

 the rib may reach the sternum, or it may articulate or fuse with 

 the first thoracic rib ; when small, it may be attached to the first 

 thoracic rib by a fibrous band, or it may present a free extremity. 

 Radiograms, taken in an antero-posterior plane, frequently fail 

 to show a cervical rib when one is present, owing to foreshorten- 

 ing consequent on its downward and forward direction. 



When the rib is well developed, both the subclavian artery 

 and the lower trunk of the brachial plexus groove its upper and 

 anterior surface. In these cases the artery occupies a higher 

 position than normal, and its pulsations are readily felt. The 

 diagnosis of aneurism may suggest itself, especially as the radial 

 pulse on the affected side is weakened, but this sign disappears 

 when the limb is elevated. Very often the rib is too short to sup- 

 port the artery, and is crossed by the nerve trunk only. Even 

 in these cases the artery lies at a higher level than normal. 



Muscular attachments are determined by the size of the rib. 

 When it is complete, or nearly so, it receives the insertions of 

 the scalenus anterior and the scalenus medius, and intercostal 

 muscles occupy the space between it and the first thoracic rib. 



A cervical rib may be present without causing any symptoms. 

 Frequently, however, the pressure on the lower trunk of the 

 brachial plexus is such that the removal of the rib must be under- 

 taken. The nervous symptoms are described on p. 100. 



Removal of a Cervical Rib. In this operation it is important 

 that the whole area should be widely exposed. This can be 

 effected by a curvi-linear incision passing down the posterior 

 border of the sterno-mastoid and turning laterally along the 

 clavicle. The external jugular vein is secured as it pierces the 

 deep fascia, and the posterior belly of the omo-hyoid is removed. 

 The fat and lymph glands which lie on the floor of the posterior 

 triangle are dissected away, and the prevertebral fascia is 

 exposed. At this stage the dorsalis scapulae nerve (to the 

 rhomboids) and the long thoracic nerve (of Bell) (p. 131) are 

 secured and traced up to their point of exit from the scalenus 

 medius. They are then retracted to one or other side, and the 

 lateral or posterior border of the scalenus medius is defined. The 

 rest of the operation is carried out behind the muscle, and in 

 this way the brachial plexus and the subclavian artery, which 

 are displaced forwards, need not be exposed. The scalenus 



