THE INTERNAL JUGULAR VEINS. 479 



The anterior jugular vein arises from the convergence of some 

 superficial branches in the submaxillary region. This vessel lies along 

 the fore part of the neck, sometimes near the sterno-mastoid m.uscle, 

 and either terminates by inclining outwards to join the external jugular 

 vein, or, after giving to it a branch of communication, sinks beneath 

 the sterno-mastoid muscle, and ends in the subclavian vein. The 

 lower ends of the two anterior jugular veins are frequently united by 

 a transverse branch placed behind the sterno-mastoid muscles and top 

 of the sternum. 



Varieties. — The external jugular vein is veiy variable in size. It is frequently 

 very small, and may be absent altogether. It is sometimes joined by the cephalic 

 vein of the arm. or by a jugulo-cephalic branch of that vein running up over 

 the clavicle. The external jugular vein has also been seen to descend in front of 

 the clavicle, and pass through the infra-clavicular fossa, to join the subclavian 

 vein beneath the clavicle. The anterior jugular vein is likewise very variable. 



Internal Jugular Veins. — These veins, receiving the blood from 

 the brain and cranial cavity, are continuous at their upper extremities 

 with the lateral sinuses within the cranium, and terminate inferiorly 

 in the innominate or brachio-cephalic veins. The commencement of 

 each internal jugular vein at the wide part {jugular fossa) of the 

 foramen jugulare, is somewhat enlarged, and has been named the sinus 

 or [lulf of the internal jugular vein. Beneath the skull, the vein is 

 supported by the rectus lateralis muscle, and lies close to the outer side 

 of the internal carotid artery, as far as the cornu of the os hyoides. 

 It is joined at this point by. the common facial vein, and becomes 

 considerably enlarged ; it then descends parallel with the common 

 carotid artery, lying at its outer side and enclosed in the same sheath, 

 together with the vagus nerve. At the root of the neck it joins 

 nearly at a right angle with the subclavian vein, and so forms the 

 innominate or brachio-cephalic vein. Close to the low-er termination 

 of the jugular, or from half an inch to an inch above it, is placed a 

 double valve as in other veins. (Struthers, " Anat. and Phys. 

 Observ.," p. 173.) 



Tributaries.— Previously to to its junction with the facial vein, the internal 

 jugular receives the lingual, pharyngeal, and occipital veins ; one or more of 

 which, however, very frequently end in the common facial trunk. 



{a) the Jinfjnal vein begins at the side and upper sm-face of the tongue, and 

 passes backwards, receiving branches from the sublingual gland ; occasionally 

 the ranine vein joins it, and sometimes also the phai-yngeal. 



{})) Th.Q pharyiifical vein commences at the back and sides of the pharj-nx, and 

 sometimes ends in the superior thyroid vein, and at other times in the lingual, 

 or separately in the internal jugular vein. 



(f) The occ'qJital vein, corresponding in course and distribution with the 

 occipital artery, communicates with a plexus of veins upon the occiput, and 

 terminates occasionally in the external jugular vein, but more frequently in the 

 internal. 



(r/) The commo7i facial vein has been already described. 



(r) The larynaml vein receives branches from the larynx through the thyro- 

 hyoid membrane, and opens into the internal jugular-, the common facial, or 

 sometimes into the superior thyroid vein. 



(/) The isvjJirior thjrotd vein commences by branches in the thyroid body, 

 in company with those of the superior thyroid artery, and runs transversely 

 outwards. 



