THE INNOM1NATA. 99 



besides which the trachea is very small and movable. 

 It sometimes gives off a branch to the thyroid body 

 (the thyroidea ima), which might lie immediately over 

 the site of the deep incision in tracheotomy ; and occa- 

 sionally it gives off thymic and bronchial branches. 



Ligature of the Innominata. In order to expose the 

 vessel for the purpose of ligaturing it, it must be drawn 

 out as much as possible from the deep position it occupies, 

 by raising the shoulders and throwing back the head. 

 Next, the sternal origin of the sterno-cleido-mastoid is 

 to be exposed, by an incision along its anterior border, 

 met by one along the upper edge of the sternum ; this 

 tendon is to be divided, and the underlying origins of 

 the sterno-hyoid and thyroid muscles carefully divided. 

 Beneath these muscular fibres is a plexus of veins, chiefly 

 derived from the inferior thyroid, which must be hooked 

 aside. The deep cervical fascia is next to be cautiously 

 scraped through, and the origin of the common carotid 

 exposed, which vessel serves as the guide to the trunk 

 of the innominate. The left innominate vein must be 

 drawn down, whilst the right innominate and internal 

 jugular veins, with the vagus nerve, are to be drawn 

 outwards. The needle must be passed from below, up- 

 wards and inwards, taking care that it is kept close to 

 the vessel, to avoid wounding the right pleura, or trachea 

 which lie behind it. The ligature should be applied as 

 high up as possible. 



Collateral Circulation developed after Ligature of the 

 Innominata. The right side of the head and neck would 

 be supplied with blood by the inosculation of the carotids 

 with those of the opposite side ; and the circulation in 

 the right subclayiaii would b$' ' reestablished; b^means 

 of its intercostal branch inosculating with the first aortic 



