The Neck. 479 



carotid felt for, and the omo-hyoid, as it crosses the artery, 

 identified. The small artery (sterno-mastoid) and the 

 middle thyroid veins, which cross the vessel are avoided, 

 and so, also, is the descendens noni nerve which lies on its 

 sheath. The latter is opened on its inner side and the 

 aneurism needle introduced from without inwards, taking 

 great care not to injure the pneumogastric nerve or the 

 internal jugular vein. In the operation below the omo- 

 hyoid the incision extends from the cricoid cartilage to 

 near the sterno-clavicular articulation ; the sterno-mastoid 

 is drawn outwards and the sterno-hyoid and sterno- 

 thyroid muscles, inwards, the inferior thyroid veins are 

 avoided and the sheath opened on its inner side. Sub- 

 clai'ian. Ligation of the third part, or of that part of the 

 vessel external to the scalenus anticus muscle, alone will 

 be considered. Operation. The external jugular vein 

 pierces the deep fascia, about one inch above the clavicle, 

 and would be in danger of being wounded if the incision 

 were made directly over it, in this region. The skin is, 

 therefore, drawn down on to the clavicle, so that an in- 

 cision made through it and the superficial fascia and pla- 

 tysma over the clavicle, will avoid this vessel. This in- 

 cision will extend from the trapezius, behind, to the 

 sterno-mastoid, in front, and its centre will be placed 

 about one inch internal to the middle of the clavicle. The 

 retraction of the skin brings the wound about half an inch 

 above the clavicle, the deep fascia is now divided and the 

 external jugular vein identified and drawn outwards and 

 the edge of the scalenus anticus muscle sought for. This 

 muscle lies behind the sterno-mastoid, and, when found, 

 the finger should follow it down to its tubercle of origin 

 on the first rib. Turning the head repeatedly to the op- 

 posite side with one hand, while the finger of the other is 

 in the wound, will often assist in identifying the scalenus 



