716 



THE VASCULAR SYSTEMS 



neck passes beneath that muscle to open into the termination of the external 

 jugular, or, in some instances, into the subclavian vein (Fig. 515). It varies con- 

 siderably in size, bearing almost always an inverse proportion to the external 

 jugular. Most frequently there are two anterior jugulars, a right and left, but 

 occasionally only one. Its tributaries are some laryngeal veins, and occasionally 

 a small thyroid vein. Just above the sternum the two anterior jugular veins com- 

 municate by a transverse trunk, which receives tributaries from the inferior thyroid 

 veins: each also communicates with the internal jugular! 1'here are no valves 

 in this vein. 



The internal jugular vein (v. jugularis intema) collectW the blood from the 

 interior of the cranium, from the superficial parts of the fa. and from the neck. 

 It is directly continuous with the lateral sinus, and commMwes in the posterior 

 compartment of the jugular foramen, at the base of the skull^Fig. 507). At its 

 origin it is somewhat dilated, and this dilatation is called the sinus or bulb of the 

 internal jugular vein (bulbus v. jugularis superior). The vein runs down the 

 side of the neck in a vertical direction, lying at first on the outer side of the internal 

 carotid artery, and then on the outer side of the common carotid artery, and at 



DORSALIS 

 LINGU/E ARTERY 

 LINGUAL VEIN 

 VEINS OF 

 DORSUM OF 

 TONGUE 



HVPOGLOSSAL 



FIG. 496. Veins of the tongue. (Testut, modified from Hirschfeld.) 



the root of the neck unites with the subclavian vein to form the innominate vein. 

 Just before its termination it is again distinctly dilated (bulbus v. jugularis in- 

 ferior}. The internal jugular vein, at its commencement, lies upon the Rectus 

 capitis lateralis, and behind the internal carotid artery and the nerves passing 

 through the jugular foramen: lower down, the vein and artery lie upon the same 

 plane, the glossopharyngeal and hypoglossal nerves passing forward between 

 them; the vagus descends between and behind them in the same sheath, and 

 the spinal accessory passes obliquely outward, behind or in front of the vein. At 

 the root of the neck the vein of the right side is placed at a little distance from the 

 artery; on the left side it usually lies over the artery at its lower part. The right 

 internal jugular vein crosses the first part of the subclavian artery. The internal 

 jugular vein is of considerable size, but varies in different individuals, the left 

 one being usually the smaller. It is provided with a pair of valves, which are 

 placed about an inch above its termination. 



Tributaries. This vein receives in its course the inferior petrosal sinus, the 

 common facial, lingual, pharyngeal, superior, and middle thyroid veins, and 

 sometimes the occipital. A tributary from the cochlea opens into the bulb of 

 the internal jugular vein. A venous plexus from the lateral sinus (plexus venosus 



