86 SURGICAL ANATOMY OF TUB 



laryngeal nerve. Behind it is the transverse process of 

 the seventh cervical vertebra, and internally the common 

 carotid itself; below and externally, this portion of the 

 subclavian artery is in relation with the pleura. 



The branches of the subclavian artery being normally 

 derived from the first part of its course, it follows that 

 on the right side these branches lie beneath the clavicu- 

 lar portion of the sterno-cleido-mastoid muscle ; and this 

 fact, added to the mechanical difficulty of reaching it, 

 forms a serious obstacle to success on placing a ligature 

 upon it in this situation. In the event of the operation 

 being undertaken, it should be tied as near the vertebral 

 as possible, so that a coagulum may be formed between 

 this point and the origin of the trunk. 



On the left side the recurrent laryngeal is not in rela- 

 tion with the subclavian artery in the neck (vide Sub- 

 clavian Artery). 



The sheath of the carotid vessels is derived from the deep 

 cervical fascia, and is divided by a septum into three 

 compartments the inner containing the artery, the ex- 

 ternal the vein, and the posterior the vagus nerve; 

 whilst either on it, or sometimes in it, is the loop formed 

 by the descendens and communicantes noni. Beneath 

 the sterno-mastoid, the relations and course of the right 

 and left common carotids are precisely similar. Their 

 course is represented by a line drawn from the sterno-cla- 

 vicular articulation, to the external aspect of the upper 

 border of the thyroid cartilage, at which level generally 

 it divides into external and internal carotid. 



The left common carotid in the neck is a little deeper 

 and rather longer than the right. 



Relations of the Cervical Portion of the Common Caro- 

 tid. In front: Integument, platysma, sternal origin of 



