THE VEINS OF THE XECK 



647 



double. It is provided with two pairs of valves, the lower pair being placed at 

 its entrance into the subclavian vein, the upper in most cases about 4 cm. above the 

 clavicle. The portion of vein between the two sets of valves is often dilated, and 

 is termed the sinus. These valves do not prevent the regurgitation of the blood, 

 or the passage of injection from below upward. 



Tributaries. This vein receives the occipital occasionally, the posterior external 

 jugular, and, near its termination, the transverse cervical, transverse scapular, and 

 anterior jugular veins; in the substance of the parotid, a large branch of commu- 

 nication from the internal jugular joins it. 



Ext. carotid 

 artery 



Suhclavian vein 

 Fia. 558. The veins of the neck, viewed from in front. 



(Spalteholz ) 



The posterior external jugular vein (. jugularis posterior) begins in the occipital 

 region and returns the blood from the skin and superficial muscles in the upper and 

 back part of the neck, lying between the Splenius and Trapezius. It runs down 

 the back part of the neck, and opens into the external jugular vein just below the 

 middle of its course. 



The anterior jugular vein (i\ jugularis anterior) begins near the hyoid bone by 

 the confluence of several superficial veins from the submaxillary region. It descends 

 between the median line and the anterior border of the Sternocleidomastoideus, 

 and, at the lower part of the neck, passes beneath that muscle to open into the ter- 

 mination of the external jugular, or, in some instances, into the subclavian vein 

 (Figs. 557, 558). It varies considerably in size, bearing usually an inverse propor- 



