STJBCLAVIAN. 



393 



Relations. It is covered, in front, by the integument, Platysma, Sterno-mastoid, 

 cervical fascia, and by the phrenic nerve, which is separated from the artery by 

 the Scalenus anticus muscle. Behind, it is in relation with the Middle scalenus. 

 Above, with the brachial plexus of nerves. Below, with the pleura. The sub- 

 clavian vein lies below and in front of the artery, separated from it by the Scalenua 

 anticus. , 



PLAN OF EELATIONS OF SECOND PORTION OF SUBCLAVIAN ARTERY. 



Infront. 



Platysma. 

 Sterno-mastoid. 

 Cervical fascia. 



Scalenus anticus. 

 Phrenic nerve. 



Subclavian Vein. 



Above. 

 Brachial plexus. 



Below. 

 Pleura. 



Behind. 

 Middle scalenus. 



The Third Portion of the Subclavian Artery passes downwards and outwards 

 from the outer margin of the Scalenus anticus to the lower border of the first 

 rib, where it becomes the axillary artery. This portion of the vessel is the most 

 superficial, and is contained in a triangular space, the base of which is formed in 

 front by the Anterior scalenus, and the two sides by the Omo-hyoid above and 

 the clavicle below. 



Relations. It is covered, in front, by the integument, the superficial fascia, the 

 Platysma, deep fascia ; and by the clavicle, the Subclavius muscle, and the supra- 

 scapular artery and vein; the clavicular descending branches of the cervical 

 plexus and the nerve to the Subclavius pass vertically downwards in front of the 

 artery. The external jugular vein crosses it at its inner side, and receives the 

 suprascapular and transverse cervical veins, which occasionally form a plexus in 

 front of it. The subclavian vein is below the artery, lying close behind the 

 clavicle. Behind, it lies on the Middle scalenus muscle. Above it, and to its 

 outer side, are the brachial plexus and Omo-hyoid muscle. Below, it rests on the 

 outer surface of the first rib. 



PLAN OF EELATIONS OF THIRD PORTION OF SUBCLAVIAN ARTERY. 



Infront. 



Integument, fasciae, and Platysma. 



The external jugular, suprascapular, and transverse cervical veins. 



Descending branches of cervical plexus. 



Subclavius muscle, suprascapular artery, and clavicle. 



Above. 



Brachial plexus. 

 Omo-hyoid. 



Below. 

 First rib. 



Behind. 

 Scalenus medius. 



Peculiarities. The subclavian arteries vary in their origin, their course, and in the height to 

 which they rise in the neck. 



The origin of the right subclavian from the innominate takes place, in some cases, above the 

 sterno-clavicular articulation; more frequently in the cavity of the thorax, below that joint. Or 



