OF THE NECK. 461 



and this dilatation is called the sinus, or gulf of the internal jugular vein. It 

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

 side of the internal carotid, and then on the outer side of the common carotid, 

 and at the root of the neck unites with the subclavian vein, to form the vena in- 

 nomiuata. The internal jugular vein, at its commencement, lies upon the Kectus 

 lateralis, behind, and at the outer side of the internal carotid, and the eighth and 

 ninth pairs of nerves ; lower down, the vein and artery lie upon the same plane, 

 the glosso-pharyngeal and hypoglossal nerves passing forwards between them ; 

 the pneumogastric descends between and behind them, in the same sheath, and 

 the spinal accessory passes obliquely outwards, behind 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 crosses it at its lower part. The vein is of considera- 

 ble size, but it varies in different individuals, the left one being usually the 

 smallest. It is provided with a pair of valves, which are placed at its point of 

 termination, or from half to three-quarters of an inch above it. 



Branches. This vein receives in its coarse the facial, lingual, pharyngeal, 

 superior and middle thyroid veins, and the occipital. At its point of junction 

 with the branch common to the temporal and facial veins, it becomes greatly 

 increased in size. 



The lingual veins commence on the dorsum, sides, and under surface of the 

 tongue, and passing backwards, following the course of the lingual artery and its 

 branches, terminate in the internal jugular. 



The pharyngeal vein commences in a minute plexus, the pharyngeal, at the 

 back part and sides of the pharynx, and after receiving meningeal branches, and 

 the Vidian and spheno-palatine veins, terminates in the internal jugular. It occa- 

 sionally opens into the facial, lingual, or superior thyroid vein. 



The superior thyroid vein commences in the substance and on the surface of the 

 thyroid gland, by branches corresponding with those of the superior thyroid artery, 

 and terminates in the upper part of the internal jugular vein. 



The middk thyroid vein collects the blood from the lower part of the lateral lobe 

 of the thyroid gland, and, being joined by some branches from the larynx and 

 trachea, terminates in the lower part of the internal jugular vein. 



The Vertebral Vein commences by numerous small branches in the occipital 

 region, from the deep muscles at the upper and back part of the neck, passes out- 

 wards, and enters the foramen in the transverse process of the atlas, and descends 

 by the side of the vertebral artery, in the canal formed by the transverse processes 

 of the cervical vertebrae. Emerging from the foramen in the transverse process of 

 the sixth cervical, it terminates at the root of the neck in the back part of the 

 innominate vein near its origin, its mouth being guarded by a pair of valves. 

 This vein, in the lower part of its course, occasionally divides into two branches ; 

 one emerges with the artery at the sixth cervical vertebra, the other escapes 

 through the foramen in the seventh cervical. 



Branches. This vein receives in its course the posterior condyloid vein, mus- 

 cular branches from the muscles in the prevertebral region ; dorsi-spinal veins, 

 from the back part of the cervical portion of the spine ; meningo-rachidian veins, 

 from the interior of the spinal canal ; and, lastly, the ascending and deep cervical 

 veiDs. 



3. VEINS OF THE DIPLOE AND INTEEIOE OF THE CRANIUM. 



VEINS OF THE DIPLOE. 



The diploo of the cranial bones is channelled, in the adult, with a number of 

 tortuous canals, which are lined by a more or less complete layer of compact 

 tissue. The veins they contain are large and capacious, their walls being thin, 

 and formed only of epithelium, resting upon a layer of elastic tissue, and they 

 present, at irregular intervals, pouch-like dilatations or culs-de-sac, which serve 



