832 THE VASCULAR SYSTEM. . ' 
in the carotid triangle, passes beneath the sterno-mastoid, and terminates in the anterior 
border of the internal jugul: wv vein. Just before it disappears beneath the sterno-mastoid, 
the common facial vein frequently gives off a large branch, which descends along the 
anterior border of the sterno-mastoid to the suprasternal fossa, where it joins the 
anterior jugular vein. 
The facial vein (v. facialis anterior, Fig. 580) commences at the inner angle of the 
orbit in the angular vein, which is formed by the union of the supraorbital and frontal 
veins. It passes downwards and backwards on the face, from the inner angle of the orbit 
to the lower and anterior part of the masseter muscle, Saini it crosses, lying in the same 
plane as the facial artery, but following a much straighter course. After crossing the 
lower border of the jaw it passes across the submaxillary triangle, superficial to the 
submaxillary gland, by which it is separated from the facial artery, which here lies in a 
deeper plane, and it terminates a short distance below the angle of the jaw by uniting 
with the anterior division of the temporo-maxillary vein to form the common facial vein. 
The facial vein receives tributaries corresponding with all the branches of the facial 
artery, except the ascending palatine and the tonsillar, which have no accompanying veins, 
the blood from the region which they supply being returned for the most part through 
the pharyngeal plexus. The facial vein also communicates, by means of an anastomosing 
channel, called the deep facial vein, which passes backwards between the masseter and 
buecinator muscles into the zygomatic fossa, with the pterygoid plexus which surrounds 
the external pterygoid muscle. 
The inferior thyroid veins have already been described (see p. 830). 
Subclavian Veins.—The subclavian vein (v. subclavia) of each side is the 
direct continuation of the main vein of the upper extremity, the axillary vein; but 
through its tributary, the external jugular vein, it also receives blood both ‘from 
the superficial and deep parts of the hee and neck. 
From its commencement at the outer border of the first rib 1t runs inwards 
below and in front of the corresponding artery, from which it 1s separated by the 
lower part of the scalenus anticus muscle, and it terminates behind the sternal 
end of the clavicle, in the innominate vein of the corresponding side. As 1b passes 
inwards 1t forms a sieht curve, the convexity of which is directed upwards. 
Each subclavian vein possesses a single bicuspid valve which is situated imme- 
chately on the distal side of the opening of the external jugular vein. 
Relations.—The subclavian vein is in relation in front with the posterior layer of the 
costo-coracoid membrane, which separates it from the subclavius muscle, and the nerve 
to the subclavius, and with the back of the sternal end of the clavicle, from which it is 
separated, however, by the fibres of the sterno-hyoid and sterno-thyroid muscles. 
It is closely atti ached in front to the posterior surface of the costo-coracoid membrane, 
consequently it is expanded when the clavicle is moved forwards, a condition of affairs 
which constitutes a distinct danger when operations are being performed in the neighbour- 
hood of the vein, for in the event of the vessel being wounded, forward movement of the 
clavicle may cause air to be sucked into the vein w ith fatal results. 
Behind the vei are the first and third parts of the subclavian artery, but it is sepa- 
rated from the second part by the scalenus anticus. ‘To the inner side of the anterior 
scalene the posterior relations of the vein, in addition to the subclavian artery, are the 
upper part of the internal mammary artery, the phrenic nerve, and the cervical portion of 
the pleura. 
It rests below upon the upper surface of the first rib. 
Tributaries.—Whilst the subclavian vein is the direct continuation of the axillary 
vein, and receives the blood from the upper extremity, it has, as a general rule, only one 
named tributary, viz. the external jugular vein. 
The external jugular vein (v. jugularis externa, Fig. 580) is formed on the 
superficial surface of the sterno- silo muscle, a little below and behind the angle 
of the jaw, by the union of the posterior auricular vein with the posterior terminal 
branch of the temporo-maaillary vein. After its formation the external jugular 
vein descends, with a slight obliquity backwards, to the anterior part of the 
subclavian portion of the posterior triangle of the neck, where it pierces the deep 
fascia, and, after crossing in front of the third part of the subclavian artery, 
terminates in the subclavian vein. 
