THE AXILLA. 447 



The phrenic and pneumogastric nerves pass between the 

 subclavian artery and vein, the pneumogastric lying 

 nearer the median line. The pneumogastric nerve in 

 the neck presents, just after it emerges from the jugular 

 foramen, a gangliaform enlargement, which sends off 

 numerous filaments of communication. It runs down 

 the neck within the sheath of the carotid artery and 

 internal jugular vein, between but behind these vessels. 

 It sends off a motor branch to the pharynx, the superior 

 laryngeal, a sensory nerve to the larynx and the recur- 

 rent laryngeal, which is given off on the right side as 

 the nerve passes over the subclavian artery ; it then 

 winds beneath and behind this trunk, runs upward to 

 the larynx, to which it is the motor nerve. On the left 

 side the recurrent laryngeal is given off below the arch 

 of the aorta ; it then runs behind this vessel along the 

 trachea to the larynx. 



The phrenic nerve is derived from the third and 

 fourth cervical ; it crosses the scalenus anticus, passes 

 into the chest between the subclavian artery and vein. 

 It is external to the pneumogastric. 



The hypoglossal passes down under cover of the 

 ramus of the inferior maxillary ; it enters the submax- 

 illary triangle, crosses the great vessels, and curves for- 

 ward to the tongue ; it sends off the descendens noni. 

 The spinal accessory nerve pierces the upper portion of 

 the stern o-mastoid, crosses the posterior superior triangle, 

 and is distributed to the trapezius. 



THE AXILLA. 



The axilla is a pyramidal space which is bounded in 

 front by the pectoral muscles ; behind, by the latissimns 

 dorsi. teres major, and subscapularis. Externally it is 



