966 



A MANUAL OF ANATOMY 



surface ol the oesophagus, and enters the abdomen through the 

 oesophageal opening of the diaphragm, to be distributed to the 

 anterior surface of the stomach. 



Differences between the Right and Left Pneumogastrie Nerves. 



Right Pneumogastrie Nerve. 



1. Descends in front of first part of 



right subclavian artery. 



2. Gives off its recurrent laryngeal 



branch at lower border of 

 right subclavian artery. 



3. Lies behind right innominate 



vein. 



4. Lies on right side of trachea. 



5. Lies at first on right side of 



oesophagus, and then behind 

 it. 



6. Ramifies on posterior surface of 



stomach. 



Left Pneumogastrie Nerve. 



1. Descends between left common 



carotid and left subclavian 

 arteries. 



2. Passes behind left innominate 



vein. 



3. Crosses in front of arch of 



aorta. 



4. Gives off its recurrent laryn- 



geal branch at lower border 

 of arch. 



5. Lies at first on left side of oeso- 



phagus, and then in front 

 of it. 



6. Ramifies on anterior surface of 



stomach. 



Branches. — ^These are as follows : the left inferior or recurrent 

 laryngeal ; cardiac, from the right nerve ; pulmonary ; oesophageal ; 

 and pericardial. 



The lefl inferior or recurrent laryngeal nerve arises from the left 

 pneumogastrie in front of the arch of the aorta, on a level with its 

 lower border. It passes backwards within the arch at the place of 

 attachment of the ligamentum ductus arteriosi, and then it turns 

 upwards behind the arch. Having reached the groove between 

 the trachea and the oesophagus, it ascends therein to the neck, 

 where its subsequent course and distribution will be described. In 

 the thorax the nerve, which contains fibres derived from the bulbar 

 or accessory portion of the spinal accessory nerve, furnishes a few 

 cardiac branches to the deep cardiac plexus as it winds round the 

 arch of the aorta. 



The right inferior or recurrent laryngeal nerve is extra-thoracic, 

 inasmuch as it arises from the right pneumogastrie at the root of 

 the neck, and it winds round the first part of the right subclavian 

 artery. 



The recurrent course of the right and left recurrent laryngeal nerves is 

 brought about by the change in position which the heart and great vessels 

 undergo in the course of development. In early embryonic life each recurrent 

 laryngeal nerve passes inwards to the larynx below the corresponding sixth 

 arterial arch. This arch on the right side, together with the fifth, disappears, 

 and the right recurrent laryngeal nerve then becomes related to the fourth 

 right arterial arch, from which the first part of the right subclavian artery is 

 developed. The sixth left arterial arch gives rise to the ductus arteriosus, 

 which, however, becomes obliterated, and then the left recurrent laryngeal 

 nerve becomes related to the fourth left arterial arch (the fifth having dis- 

 appeared) at the place where it receives the ductus arteriosus, and from this 

 fourth left arch the arch of the aorta is developed. As the heart and great 

 vessels descend from the neck into the thorax each recurrent laryngeal 



