1 82 Thoracic Ancutysin 



upon the recurrent laryngeal nerve, altering the voice and paralysing 

 the muscles of the left cord (p. 70) ; upon the oesophagus, causing 

 dysphagia and suggesting stricture of the gullet (p. 139) ; upon the 

 thoracic duct, causing inanition ; upon the left innominate vein, pro- 

 ducing duskiness, venous congestion, and oedema of the left side of the 

 head and neck and of the left arm, and possibly causing at last absorption 

 of the manubrium. When the sac bulges into the episternal region the 

 case may be taken for one of aneurysm of one of the aortic trunks; and 

 the tumour may cause compression and even obliteration of the left 

 carotid or subclavian artery, thereby increasing the risk of error in 

 diagnosis. Should it bulge into the neck the resemblance to an 

 aneurysm of the innominate or common carotid may lead to error of 

 diagnosis. 



More than once it has happened, unfortunately, that tracheotomy has 

 been resorted to for the relief of dyspnoea which happened to be caused 

 by pressure of an aortic aneurysm upon the trachea. When, however, 

 it can be made out that the dyspnoea is due to pressure upon the 

 left recurrent laryngeal nerve, the windpipe may be opened with ad- 

 vantage. 



Aneurysm of the third part of the arch pulsates against, and may 

 bulge through, the vertebral ends of the middle ribs of the left side, 

 causing at first intercostal neuralgia and obscure dorsal pains sugges- 

 tive of caries ; then, reaching the spinal canal, it may determine para- 

 plegia ; and by pressing on the left pulmonary plexus, which is just in 

 front of it, may cause spasmodic attacks like those of asthma, so that 

 eventually air may entirely fail to enter the lung. It may press against, 

 and eventually burst into, the oesophagus, trachea, left bronchus, peri- 

 cardium, or pleura. 



The innominate artery, \\ in., arises at the beginning of the trans- 

 verse aorta, behind the middle of the manubrium ; passing upwards 

 and to the right, it divides at the upper border of the right sterno-clavi- 

 cular joint, between the heads of the sterno-mastoid muscle. 



Relations. Separating it from the manubrium are the origins of 

 the sterno-hyoid and thyroid and the remains of the thymus gland ; it is 

 crossed by the left innominate vein and the right inferior thyroid veins. 

 Behind is the trachea. To tlic left are the trachea and the left carotid ; 

 and to the right are the pleura and lung, with the right innominate 

 vein and pneumogastric nerve. 



Varieties. The innominate artery may bifurcate in the thorax, or 

 it may pass into the root of the neck before dividing. Sometimes it 

 gives off the thyroidea ima, an irregular branch, to the lower part of 

 the thyroid body, which, however, is occasionally derived from the left 

 carotid, or from the transverse aorta itself. This little artery ascends 

 to the thyroid body on the front of the trachea, and may be wounded 

 in tracheotomy below the isthmus. 



Xtigation of tbe innominate artery is a desperate operation, as 



