1228 A MANUAL OF ANATOMY 



forwards behind the internal carotid artery, having previously 

 received communicating branches from the superior cervical 

 ganglion of the sympathetic and from the pharyngeal plexus. As 

 it passes behind the internal carotid artery, it divides into two 

 branches, internal and external. The internal laryngeal nerve, 

 which is sensory, passes forwards, in company with the superior 

 laryngeal branch of the superior thyroid artery, to the thyro-hyoid 

 membrane, which it pierces under cover of the posterior border of 

 the thyro-hyoid muscle. Having reached the interior of the larynx, 

 it divides into branches which supply the mucous membrane of the 

 epiglottis, with its folds, the mucous membrane of the lar5mx as low 

 as the true vocal cords, and that covering the lateral and posterior 

 portions of the cricoid cartilage. One branch descends over the 

 inner surface of the ala of the thyroid cartilage, and joins a branch 

 of the inferior or recurrent laryngeal. The external laryngeal 

 nerve, of small size, descends beneath the sterno-thyroid muscle to 

 the crico-thyroid muscle, which it supplies. It furnishes some twigs 

 to the inferior constrictor, and a filament which joins the superior 

 cardiac branch of the sympathetic. It receives a communicating 

 branch from the superior cervical ganglion of the sympathetic, 

 and one or two branches from the pharyngeal plexus. 



Inferior or Recurrent Laryngeal Nerve. — ^This nerve is mainly 

 motor, and is the principal motor nerve of the intrinsic muscles of 

 the larynx. It contains fibres of the bulbar or accessory portion of 

 the spinal accessory nerve. The right nerve arises from the pneumo- 

 gastric at the root of the neck in front of the first part of the sub- 

 clavian artery, round the lower border of which it bends, and then 

 ascends behind it. Thereafter it passes upwards and inwards 

 behind the carotid sheath and inferior thyroid artery to the groove 

 between the trachea and the oesophagus. The left nerve arises 

 in the thorax from the pneumogastric 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. The right and left nerves pass upwards 

 in the groove between the trachea and the oesophagus, on each side, 

 lying behind the corresponding inferior thyroid artery. At the 

 level of the cricoid cartilage each nerve passes beneath the lower 

 border of the inferior constrictor muscle, and enters the larynx 

 behind the crico-thyroid joint. 



Extralaryngeal Branches. — (i) Communicating twigs pass between 

 the recurrent laryngeal nerve and the inferior cervical ganglion of 

 the sympathetic ; (2) cardiac branches, which contain bulbar fibres 

 from the spinal accessory, are furnished to the deep cardiac plexus ; 

 (3) tracheal and (esophageal branches are supplied to these tubes ; 

 and (4) muscular offsets pass to the lower part of the inferior con- 

 strictor. 



Intralaryngeal Branches. — ^These are chiefly muscular, and \ apply 



