482 



THE BLOOD-VASCULAR SYSTEM. 



throughout the whole or greater part of its attachment. By pressing aside any loose i-ellular 

 tissue or vessels that may now appear the Sterno-hyoid and Sterno-thyroid muscles will be 

 exposed, and must be divided, a director being previously passed beneath them. The inferior 

 thyroid veins may come into view, and must be carefully drawn, either upward or downward, by 

 means of a blunt hook, or tied with double ligatures and divided. After tearing through a 

 strong fibre-cellular lamina, the right carotid is brought into view, and, being traced downward, 

 the arteria innominata is arrived at. The left innominate vein should now be depressed ; the 

 right innominate vein, the internal jugular vein, and the pneumogastric nerve drawn to the right 

 side ; and a curved aneurism needle may then be passed around the vessel, close to its surface, 

 and in a direction from below upward and inward, care being taken to avoid the right pleura! 

 sac. the trachea, and cardiac nerves. The ligature should be applied to the artery as high as 

 possible, in order to allow room between it and the aorta for the formation of the coagulum. 

 The importance of avoiding the thyroid plexus of veins during the primary steps of the opera- 

 tion, and the pleural sac whilst including the vessel in the ligature, should be most carefully borne 

 in mind. After the artery has been secured, the common carotid should be tied about half an 

 inch above its origin, and also the thyroidea ima if the vessel is of any size. The several 

 muscles are united by buried sutures. 



ARTERIES OF THE HEAD AND NECK. 



The artery which supplies the head and neck is the Common Carotid : it ascends 

 in the neck and divides into two branches : the External Carotid, supplying the 

 superficial parts of the head and face and the greater part of the neck ; and the 

 Internal Carotid, supplying to a great extent the parts within the cranial cavity. 



The Common Carotid Arteries. 



The common carotid arteries, although occupying a nearly similar position in 

 the neck, differ in position, and, consequently, in their relation at their origin. 

 The right carotid arises from the innominate artery, behind the right sterno- 

 clavicular articulation ; the left from the highest part of the arch of the aorta. 

 The left carotid is, consequently, longer, and at its origin is contained within the 

 thorax. The course and relations of that portion of the left carotid which inter- 

 venes between the arch of the aorta and the left sterno-clavicular articulation will 

 first be described (see Fig. 280). 



The left carotid within the thorax ascends obliquely outward from the arch of 

 the aorta to the root of the neck. In front, it is separated from the first piece of 

 the sternum by the Sterno-hyoid and Sterno-thyroid muscles, the left innominate 

 vein, and the remains of the thymus gland ; behind, it lies on the trachea, oesoph- 

 agus, and thoracic duct. Internally, it is in relation with the innominate 

 artery, inferior thyroid veins and remains of thymus gland ; externally, with the 

 left pneumogastric nerve, left pleura, and lung. The left subclavian artery is 

 posterior and slightly external to it. 



PLAN or THE RELATIONS OF THE LEFT COMMON CAROTID. 

 THORACIC PORTION. 



In front. 

 Sternum. 



Sterno-hyoid and Sterno-thyroid muscles. 

 Left innominate vein. 

 Remains of thymus gland. 



Internally. 



Innominate artery. 

 Inferior thyroid veins. 

 Remains of thymus gland. 



Externally. 



Left pneumogastric nerve. 

 Left pleura and lung. 

 Left subclavian artery. 



Behind. 



Trachea. 

 (Esophagus. 

 Thoracic duct, 

 Left subclavian artevv. 



