VENOUS SYSTEM. 



1405 



The temporal vein is formed by the union of 

 two branches, which represent the superficial 

 and middle temporal arteries. 



The ruperficial temporal veins form a wide- 

 spreading network of vessels on the lateral 

 aspect of the scalp, which communicates with 

 the frontal veins in front, with the occipital 

 behind, and with the temporal veins of the 

 opposite side across the vertex. 



The middle temporal veins arise in the sub- 

 stance of the temporal muscle, where they 

 are joined, behind the external orbital process, 

 by branches from the orbit : these veins, by 

 their union, form a branch which is placed at 

 first between the temporal muscle and fascia, 

 but subsequently perforates the latter imme- 

 diately above the zygoma, and forms with the 

 superficial temporal vein a common trunk, 

 which enters the parotid gland, and unites 

 with the internal maxillary vein. 



Internal maxillary vein. In the pterygoid 

 space the branches of veins which correspond 

 to those given off in the same region by the 

 internal maxillary artery, viz. the inferior dental, 

 deep temporal, pterygoid, and (according to 

 Cruveilhier) the middle meningeal veins (vence 

 comites to the middle meningeal artery, which 

 communicate in the cranium with the inferior 

 cerebral veins), unite to form a great venous 

 plexus placed between the pterygoid muscles, 

 which communicates freely, as has been men- 

 tioned, with the facial vein. Arising from 

 this plexus, the internal maxillary vein passes 

 backwards nlong with its artery, between the 

 ramus of the jaw and the internal lateral liga- 

 ment of the temporo-maxillary articulation, 

 and entering the parotid gland joins the tem- 

 poral vein ; by the union of these branches the 

 external jugular vein is formed. Many ana- 

 tomists give to the upper portion of the venous 

 trunk, formed in the manner which has just 

 been described, the name of temporo-max- 

 illary vein, by others it is designated posterior 

 facial, names which are applied to it until it 

 has emerged from the parotid gland, where, 

 according to these authorities, the proper 

 external jugular vein commences. 



The temporo-maxillary vein (or that stage 

 of the external jugular vein which is contained 

 in the parotid gland) is joined by the branches 

 which accompany the transverse facial and 

 posterior aural arteries, and sends off a large 

 communicating branch, which unites with the 

 facial vein. 



The temporo-maxillary vein is situated more 

 superficially than the external carotid artery, 

 which it separates from the plexiform rami- 

 fications of the portio dura nerve. 



On the posterior region of the head is found 

 the occipital vein. The ramifications of this 

 vein are spread over the posterior portion of 

 the scalp, and correspond very accurately to 

 the terminal branches of the occipital artery; 

 the trunk which they form likewise accom- 

 panies that of the artery, passes with it beneath 

 the splenius and sterno-mastoid muscles, and 

 joins the internal jugular vein below the di- 

 gastric muscle ; less "frequently it unites with 

 the external jugularvein. Opposite the mastoid 



process, the occipital vein is joined by several 

 branches from the mastoid region, one of 

 which passes through a canal in the bone 

 (mastoid hole), and communicates directly 

 with the lateral sinus of the dura mater. 



2. Veins of the neck. The most remarkable 

 of these are the internal and external jugular, 

 and the vertebral veins. 



External jugular vein. This vessel is the 

 principal channel of the superficial venous 

 circulation of the neck. Its direction is down- 

 wards and slightly outwards, and it extends 

 from the lower margin of the parotid gland to 

 the subclavian vein. Crossing the sterno-mas- 

 toid obliquely, the external jugular vein de- 

 scends parallel to the posterior edge of that 

 muscle, through the supra-clavicular space, and 

 lies on the deep cervical fascia, by which it is 

 separated from the omohyoid muscle, bra- 

 chial plexus, and subclavian artery. Finally, 

 the vein passes forwards through an opening 

 in the fascia cervicalis, and joins the subcla- 

 vian vein. Several of the nerves of the cer- 

 vical plexus are related to this vein ; many 

 of their branches cross it as they descend the 

 neck ; and the largest of the three ascending 

 branches of the plexus, the nervus auricularis 

 magnus, is parallel to the vein and to its outer 

 side, as it lies on the sterno-mastoid muscle. 



Throughout the entire of its extent the ex- 

 ternal jugular vein is covered by the fibres of 

 the platysma myoides, which cross its direc- 

 tion obliquely forwards and inwards. This 

 vein is furnished with two sets of valves, one 

 of which is placed at its entrance into the sub- 

 clavian vein, and by this circumstance the ex- 

 ternal jugular is distinguished from all other 

 veins of the head "or neck, in none of which 

 are valves found to exist. 



The branches which the external jugular 

 vein receives are the following : first, several 

 large veins from the posterior region of the neck ; 

 one of these, which from its superior size, and 

 also from its position, may be distinguished by 

 the name of posterior jugular vein, descends 

 from beneath the trapezius muscle, through 

 the postero-superior triangle of the neck, and 

 joins the external jugular vein a little below 

 its centre. Lower down this latter vein re- 

 ceives, secondly, the " venae comites" of the 

 superior and posterior scapular arteries. By 

 its anterior surface the external jugular vein 

 receives; thirdly, muscular branches', fourthly, 

 a communicating branch, which passes be- 

 neath the sterno-mastoid muscle, and joins 

 the internal jugular vein ; and sometimes, 

 fifthly, the anterior jugular vein. 



Anterior jugular vein. This vein is but 

 seldom absent, although its size is subject to 

 much variety ; in general its development is 

 inversely as that of the external jugular 

 trunk, to which it is to be regarded as sup- 

 plemental. The branches of origin of the 

 anterior jugular vein are derived from several 

 small muscular and cutaneous veins of the 

 supra-hyoid region, which generally communi- 

 cates with the facial veins. Thus formed, this 

 vein passes down by the side of the larynx 

 along the anterior margin of the sterno- 



