Innominate Artery 183 



the trunk may happen to be altogether intra-thoracic dividing low 

 down. In reaching it there may be alarming hasmorrhage from an 

 accidental or inevitable wound of the right inferior thyroid vein, or of 

 the left innominate vein ; or the right vein, or even the vena cava 

 itself, may be pierced by the aneurysm-needle working in the depths 

 of the wound and in the dark. The pleura may be damaged and 

 become inflamed, or fatal secondary haemorrhage may occur on 

 account of imperfect plugging of the artery after the application of the 

 ligature. After tying the innominate, a ligature should also be placed 

 upon the common carotid artery so as to prevent the collateral circu- 

 lation interfering with the formation of firm clots. 



Operation. The shoulders are raised so that the head may be 

 thrown back with the view of pulling upon the carotid and raising the 

 innominate to the utmost, the right arm being drawn well down. The 

 root of the sterno-mastoid is to be raised by an L-shaped incision, one 

 limb of which runs down the anterior border, whilst the other detaches 

 at least the sternal head, each limb of the |_ being at least two inches 

 long. The skin, superficial fascia, platysma, and deep fascia are 

 divided, layer by layer, until the sterno-mastoid is reached. After re- 

 flection of the large muscle the sterno-hyoid and thyroid are divided 

 on a director, and the right inferior thyroid veins are seen and care- 

 fully hooked aside, or, if necessary, tied and severed. 



The root of the carotid is then sought and followed down until the 

 innominate trunk is reached. The left innominate vein is then de- 

 pressed, the right being drawn downwards and to the right, and the 

 aneurysm-needle is gently passed from the venous, the pneumo- 

 gastric and pleural side the outer side upwards and inwards. 



To find the channels by which collateral circulation may be estab- 

 lished, the best plan is to follow the empty trunk and to see what branches 

 from it, or from its divisions, are likely to meet with well-filled vessels. 

 Such branches quickly imbibe blood and bring it in the opposite direc- 

 tion to that in which they were accustomed to convey it towards the 

 occluded part. Thus the right common carotid divides into the external 

 and internal carotids ; the external gives off the superior thyroid, 

 lingual, facial, occipital, temporal, and internal maxillary, which would 

 bring in blood from their fellows of the opposite side. 



The internal carotid would bring blood by the anterior communi- 

 cating from the opposite side. The anastomosis through the posterior 

 communicating would not serve, as the posterior cerebral which it joins 

 has, because of the ligature, no blood to render ; it might, however, 

 obtain a little blood from the left vertebral through the basilar. 



The subclavian trunk would be very serviceable : by the internal 

 mammary it would bring up blood from the aortic intercostals, the 

 deep epigastric of the external iliac, and the phrenics. The vertebral 

 would bring blood direct from the basilar and from branches of its 

 fellow of the opposite side. The inferior thyroid would bring in blood 



