588 



DISSECTION OF THE NECK. 



Dissection 



of the 



subclavian 



artery 



and its 

 branches ; 



of thoracic 

 duct. 



Right lym- 

 phatic duct 



of brachial 

 plexus ; 



uf cervical 

 plexus. 



Directions. The remaining parts included in this section are the 

 scaleni muscles and the subclavian blood-vessels, with the cervical 

 nerves and the carotid blood-vessels. The student may examine 

 them in the order here given. 



Dissection (fig. 213). The Bterno-mastoid is to be cut and the 

 fat and fascia taken away from the lower part of the neck so as to 

 prepare the scaleni muscles with the subclavian vessels and their 

 branches. By means of a little dissection the anterior scalenus 

 muscle will be seen ascending from the first rib to the lower 

 cervical vertebrae, having the phrenic nerve and subclavian vein in 

 front of it, the latter crossing it near the rib. 



The part of the subclavian artery on the inner side of the 

 scalenus is then to be cleaned, care being taken not only of its 

 branches, but also of the branches of the sympathetic nerve which 

 course over and along it from the neck to the chest. This dissec- 

 tion will be facilitated by the removal of the inner part of the 

 clavicle. 



All the branches of the artery are in general easily found, except 

 the superior intercostal, which is to be sought in the thorax in 

 front of the neck of the first rib. On, or near, the branch (inferior 

 thyroid) ascending behind the carotid sheath to the thyroid gland, 

 is the middle cervical ganglion of the sympathetic ; and the 

 dissector should follow downwards from it a small cardiac nerve to 

 the thorax. Only the origin and first part of the arterial branches 

 can be now seen ; their termination is met with in other stages of 

 the dissection. 



On the left side the student should seek the thoracic duct a.s it 

 arches over the part of the subclavian artery internal to the scalenus 

 muscle. If it is uninjected it looks like a vein, rather flattened, 

 and smaller than a crow-^uill ; and it will be found about half an 

 inch above the clavicle, crossing behind the internal jugular vein, 

 and then bending downwards to end in the angle between the latter 

 and the subclavian vein. 



The small right lymphatic duct at its entry into the veins in a 

 corresponding position 011 the right side should also be found. 



The outer part of the subclavian artery having been already 

 prepared, let the dissector remove more completely the fibrous 

 tissue from the nerves of the brachial plexus. From the plexus 

 trace down the small branch to the subclavius muscle in front of 

 the subclavian vessels, and the branches to the rhomboid and 

 serratus muscles, which pierce the middle scalenus. If it is thought 

 necessary, the anterior scalenus may be cut through after the 

 artery has been studied. 



Clean the cervical plexus, beginning with the nerves at their 

 emergence in the neck in front of the origins of the scalenus 

 medius and tracing them from this. Seek the muscular branches, 

 the small twigs to join the descendens cervicis from the hypo- 

 glossal, and the roots of the phrenic nerve. Lastly, let the 

 middle scalenus muscle be defined, as it lies beneath the cervical 

 nerves. 



