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 (venue 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 along with its artery, between the ramus of the jaw and the internal lateral lige incnt of the temporo•maxillary articulation, and 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 tenzporo-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 temnoro-maxillary vein is situated more superficially than the external carotid artery, which it separates from the plexiform rami fications of the portio Jura 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 the internal jugular vein below the di .gastric muscle ; less frequently it unites with the external jugular vein. 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 (lure mater.
2. Veins of 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, owe 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 front 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 " venm 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 us 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-. sates with the facial veins. Thus formed, this vein passes down by the side of the larynx along the anterior margin of the sterno mastoid muscle, beneath which it passes, a little above the clavicle, to join the internal jugular vein, close to the junction of the latter with the subclavian vein.