84 Roaring in Horses. 



directed backwards and slightly upwards, bending from left 

 to right round the posterior surface of the ligamentum arteri- 

 osus, and passing over the internal face of the pulmonary 

 artery ; then it proceeds upwards, inwards, and forwards, to 

 the lower surface of the trachea, to Avhich it is attached by 

 connective tissue, and there it is also bridged over by an ex- 

 pansion of the endo-thoracic fascia, which is connected with 

 the pericardium. In passing along the trachea, the nerve 

 gradually ascends to gain the left side of that tube, above, 

 but very close to the tracheal lynvphatic glands. The re- 

 lations of the nerve to lymphatic glands and to the pleural 

 membrane are very intimate; as from its origin until it reaches 

 the trachea it is placed between the pleura and pericardium, 

 and when crossing the pulmonary artery it is enveloped in 

 a quantity of connective tissue that supports the bronchial 

 lymphatic glands, while behind the aorta it gives off numer- 

 ous fibres that may be traced to the surface of these 

 glands. 



Before leaving the bronchial glands, the nerve is con- 

 stantly found intimately related to a median branch of the 

 inferior cervical ganglion, and this relationship is main- 

 tained to within two or three inches from this ganglion ; 

 some of the fibres of this sympathetic branch also pass to 

 the surface of the glands. It is also to be noted that the 

 angle separating this nerve from the vagus nerve is partly 

 occupied by nerve fibres, which pass from one nerve to the 

 other. 



Giving off twigs to the trachea and oesophagus, the nerve 

 passes out of the chest and up the left side of the neck in 

 the same manner as the right nerve, and is ultimately dis- 

 tributed to all the left laryngeal muscles except the crico- 

 thyroid. 



It will thus be seen that the left recurrent nerve differs 

 most materially from the right, not only in its peculiar 

 relations with the pleural membrane and its fasciae in 

 immediate proximity to most important organs (lungs and 



