Chap, ix.] THE NECK. 165 



carotid and subclavian arteries for innominate aneur- 

 ism. Since in this procedure large branches come off 

 between the sac and the ligature, it is not easy to fully 

 understand how the operation acts beneficially. It is 

 assumed to owe its success to the same principle that 

 underlies Brasdor's operation. The right carotid and 

 subclavian have also been ligatured for aortic aneurism 

 with some success, and here also the reason for the 

 good effected by the operation is difficult to appreciate. 

 It has been pointed out that the innominate artery 

 lies more or less directly in the axis of the ascending 

 aorta, while the left carotid and subclavian arteries 

 arise at an angle to that axis, and it is upon this fact 

 that reasons have been founded for selecting the 

 vessels of the right side (Bar well). The matter is, 

 however, complicated by the knowledge that when 

 vegetations are swept off the aortic valves they enter 

 the left carotid with infinitely greater frequency than 

 they do the right. The whole subject, indeed, requires 

 investigation. 



The cervical connective tissue being lax, aneurisms 

 in this part can grow and spread rapidly, and usually 

 soon produce "pressure symptoms." As examples of 

 these may be noted oedema and lividity of the face or 

 the upper limb from pressure upon the main veins, 

 laryngeal symptoms from pressure upon the recurrent 

 nerve or trachea, spasm of the diaphragm from pres- 

 sure upon the phrenic nerve, damage to the sympa- 

 thetic, and giddiness and impaired vision from anaemia 

 of the brain. 



The vertebral artery has been ligatured with some 

 benefit in cases of epilepsy. The artery is reached 

 through an incision made along the posterior border 

 of the sterno-mastoid muscle just above the clavicle. 

 The "carotid tubercle" (see page 137) is then sought 

 for, and vertically below it the artery lies in the gap 

 between the scalenus anticus and longus colli muscles. 



