340 SPECIAL ANATOMY. 



between the skin and muscular layer, unite above the proc. 

 zygomat. of the temporal bone, and unite before the external 

 auditory meatus with : 



b. V. temporalis media; passes under fascia media; over m. tem- 

 poralis from before backwards, perforates the fascia ; consists of: 

 vv. palpebral. and orbitales externce, 



2. Maxillaris interna corresponds to the inferior portion of art- 

 maxillar. intern. ; receives two vv. meningeos media, v. dentalis infe- 

 rior, vv. temporal., profundee, pterygoidece, massetericce ; they form 

 plexus pterygoideus in the inferior part of the temporal fossa, be- 

 tween m. temporal, and pt erygoid. extern, and the two pterygoidei. 



3. Vv. parotidecB, auricular es poster, and anter., t ransversa faciei form 

 between Parotis, m. masseter, and about the maxillary articulation, 

 the large plexus massetericus, which is connected above the incisura 

 semilunar. with pi. pterygoid. 



c. V. occipitalis passes under m. splenius forwards, and receives several 

 vv. mastoidece, which pass out of sinus transvers. of the cranial cavity, 

 and they establish an important communication between the external and 

 internal cranial veins. 



d. Ven. thyreoidea superior ; its branches come from the superior part of 

 the thyroid gland, from below the pharynx, from the interior of the 

 larynx ; it opens into the short trunk of cephalica externa ; likewise the 

 laryngea and lingualis (s. jugular, externa). 



e. V. thyreoidea media arises from art. tkyr. infer., opens into the trunk of 

 jugular, interna. 



593. Jugularis externa consists of an anterior and posterior (cutaneous) 

 trunk, which open together behind the clavicle, and enter into the V. sub- 

 clavia or V. anonyma. They have (two) valves. 



1. Jugularis externa anterior, formed by one or two vv. subcutanecs above 

 the hyoid bone, descends along the inner border of m. sterno-cleido-mas- 

 toideus, and curves backwards behind the inferior termination of the 

 muscle to the posterior trunk. A transverse branch unites the right and 

 left vein, and generally receives the V. thyreoid. media ; a superior 

 transverse branch unites both in the region of the os hyoides. 



2. Jugularis externa anterior. Origin: behind the angle of the lower 

 jaw, from a branch of V.facialis posterior, V. occipitalis, and auricular, 

 superfic. Course: oblique from above downwards, and from before 

 backwards, over the sterno-cleido-mast. ; from the angle of the lower jaw 

 as far as the centre of the clavicle, then forwards and inwards to the 

 v. subclavia. Position: superficial, covered by M. platysmam. and skin 

 only: above, behind it N. auricularis ; below, behind m. sterno-cleido- 

 mast. Branches ; besides the principal rami : 



a superior connecting branch through the Parotis with V. Jugularis 

 interna : 



