THH EXTERNAL JUGULAR YETX. 517 



the internal pterygoid. It receives tributaries which are mostly companion veins of 

 the branches of the internal maxillary artery. Thus, three or four deep temporal 

 veins descend from the temporal muscle, and other branches come from the pterygoid 

 and masseter muscles ; a posterior denial or alveolar branch ascends from the surface 

 of the upper jaw, and another of larger size, inferior dental, from the canal in the 

 lower jaw ; two middle meningeal veins accompany the artery of the same name ; 

 and lastly, superior palatine, infraorlital ', and splieno-palatine veins, as well as a com- 

 municating branch from the inferior ophthalmic vein, also enter the plexus. The 

 blood is conveyed from the plexus by the deep facial vein (p. 515) anteriorly, and 

 posteriorly by the single or double internal maxillary vein. 



The posterior auricular vein, of large size in comparison with the artery of 

 the same name, collects the blood from the hinder part of the side of the head 

 and from the cranial surface of the auricle ; it descends over the mastoid process 

 and the upper end of the sterno-rnastoid muscle, to terminate in the external jugular 

 vein. 



The occipital veins, generally two or three in number, issue from the hind- 

 most part of the venous network of the scalp, the most external being also connected 

 in most cases with the lateral sinus within the skull by means of the emissary vein 

 occupying the mastoid foramen (this vein sometimes joins a branch of the posterior 

 auricular) ; descending over the occipital bone, they pass deeply between the muscles 

 of the back of the neck, and empty themselves into .the commencement of the deep 

 cervical vein. 



External jugular vein. This vein commences near the angle of the jaw by 

 the union of the posterior auricular and the posterior division of the temporo- 

 maxillary veins. It descends with- a nearly vertical course between the platysma 

 myoides and the fascia, crossing the sterno-mastoid obliquely and gaining the pos- 

 terior border of that muscle below. Near the clavicle it perforates the fascia, the 

 margin of the opening being closely united to the wall of the vessel, and then 

 inclines slightly inwards to terminate most frequently in the subclavian vein at the 

 outer border or in front of the anterior scalenus muscle, but sometimes in the lower 

 end of the internal jugular, or in the angle between the two large veins. It is 

 joined below the middle of the neck by a considerable vein (posterior external 

 jugular), which descends from the occipital region, collecting branches from the 

 integument and the superficial muscles of the back of the neck, and near its ter- 

 mination by the transverse cervical and suprascapular veins from the shoulder, cor- 

 responding to the arteries of the same name, as well as usually by the anterior 

 jugular vein from the fore part of the neck. 



The external jugular vein has an imperfect valve close to its termination, and 

 another, which however is generally sufficient to prevent regurgitation, about an inch 

 and a half above the clavicle. There are also valves in the transverse cervical and 

 suprascapular veins, either at or a short distance from their orifices. 



The anterior jugular vein takes its origin in the submaxillary region by the 

 union of branches, some of which proceed from the superficial structures of this part 

 and ' form communications with the submental vein, while others descend from the 

 lower lip and chin. The vessel runs down the front of the neck, being placed a 

 variable distance from the middle line, and frequently being connected by one or 

 more cross branches with the external jugular vein ; near the inner end of the 

 clavicle it perforates the fascia, and, after being joined in most cases by a commu- 

 nicating branch from the facial vein, is then directed outwards behind the origin of 

 the sterno-mastoid muscle to open into the lower end of the external jugular vein, 

 or sometimes directly into the subclavian vein. The lower parts of the two anterior 

 jugular veins are generally united by a transverse branch contained in the inter- 

 fascial space at the upper border of the sternum (p. 297). 



