148 APPLIED ANATOMY. 



The first portion of the subclavian lies very deep and operations on it have been 

 so unsuccessful that they have been practically abandoned. As it is frequently 

 involved in aneurisms its relations are worth studying. In approaching the artery 

 from the surface it is seen to be covered by the sternomastoid, the sternohyoid, 

 and the sternothyroid muscles. The outer edge of the sternomastoid muscle corre- 

 sponds with the outer edge of the scalenus anticus. The three first-named muscles 

 having been raised, the artery is seen to be crossed by the internal jugular, the 

 vertebral, and perhaps the anterior jugular veins. The anterior jugular above the 

 clavicle dips beneath the inner edge of the sternomastoid muscle to pass outward 

 and empty into the external jugular or subclavian. The pneumogastric nerve crosses 

 the artery just to the inner side of the internal jugular vein. Below, the artery rests 

 on the pleura, and on the right side the recurrent laryngeal nerve winds around it. 

 Behind the artery are the pleura and lung, which rise somewhat higher in the neck 

 than does the artery. 



On the left side the phrenic nerve leaves the scalenus anticus muscle at the first 

 rib, crosses the subclavian at its inner edge, and passes down on the pleura to cross 

 the arch of the aorta. To the inner side of the artery runs the thoracic duct, which, 

 as it reaches the upper portion of the artery, curves over it to cross the scalenus 

 anticus muscle and empty into the junction of the internal jugular and subclavian 

 veins. The trachea and oesophagus are likewise seen to the inner side of the artery. 

 The thyroid axis comes off its anterior surface, the vertebral from its posterior, and 

 the internal mammary below. 



. The second portion of the subclavian artery lies behind the anterior scalene 

 muscle. In front of the anterior scalene is the subclavian vein. The phrenic nerve 

 runs on the muscle and at the first rib leaves it to continue down between the right 

 innominate vein and pleura. Behind and below, the artery rests on the pleura and 

 the middle scalene muscle is to its outer side. Thus it is seen that the artery passes 

 through a chink formed by the anterior scalene muscle in front and the middle 

 scalene behind. They both insert into the first rib. The posterior scalene is farther 

 back and inserts into the second rib. Above the artery are all the cords of the 

 brachial plexus. One branch of the subclavian, the superior intercostal artery, is 

 given off near the inner edge of the anterior scalene muscle. 



The third portion of the subclavian runs from the outer edge of the anterior scalene 

 muscle to the lower border of the first rib. This part of the artery is the most super- 

 ficial. The only muscle covering it above is the thin sheet of the platysma, lower 

 down the subclavius muscle and clavicle overlie it; but the operations on the vessel 

 are done above these structures, hence they do not interfere. There are apt to be a 

 number of veins in front of the artery. The external jugular and transverse cervical 

 veins are certain to be present and perhaps the suprascapular and cephalic, which 

 may enter above instead of below the clavicle. These veins may form a regular net- 

 work in the posterior cervical triangle above the clavicle and prove very troublesome. 

 Above is the brachial plexus and transverse cervical artery and still higher is seen the 

 omohyoid muscle. The suprascapular artery is lower down and usually concealed 

 just below the upper edge of the clavicle. The lowest cord of the brachial . plexus, 

 formed by the first dorsal and last cervical nerves, may be posterior to the artery. 

 The nerve to the subclavius muscle passes down in front of it. 



Ligation of the Third Portion of the Subclavian Artery. The head is to be 

 turned strongly to the opposite side and the shoulder depressed. This lowers the 

 clavicle and raises the omohyoid muscle and therefore gives more room to work. 

 The skin is to be drawn down and an incision 7.5 cm. long made on the clavicle. 

 The drawing down of the skin is done to avoid wounding the external jugular vein. 

 This vein is really fastened to the deep fascia, and the skin, platysma, and super- 

 ficial fascia slide over it. On releasing the skin it slides up above the clavicle. The 

 middle of the incision should be a little to the inside of the middle of the clavicle. 

 The deep fascia is to be incised and the clavicular origin of the sternomastoid 

 and trapezius muscles cut to the same extent as the superficial incision. The length 

 of the adult male clavicle is about 15 cm. (6 in.). 



The clavicular origin of the sternomastoid extends out on the clavicle one-third 

 of its length. The trapezius inserts into the outer third. This leaves the middle 



