660 ANGIOLOGY 



receives the internal auditory veins and also veins from the medulla oblongata, 

 pons, and under surface of the cerebellum. 



The exact relation of the parts to one another in the jugular foramen is as follows : 

 the inferior petrosal sinus lies medially and anteriorly with the meningeal branch 

 of the ascending pharyngeal artery, and is directed obliquely downward and back- 

 ward; the transverse sinus is situated at the lateral and back part of the foramen 

 with a meningeal branch of the occipital artery, and between the two sinuses are 

 the glossopharyngeal, vagus, and accessory nerves. These three sets of structures 

 are divided from each other by two processes of fibrous tissue. The junction of the 

 inferior petrosal sinus with the internal jugular vein takes place on the lateral 

 aspect of the nerves. 



The basilar plexus (plexus basilaris; transverse or basilar sinus} (Fig. 571) con- 

 sists of several interlacing venous channels between the layers of the dura mater 

 over the basilar part of the occipital bone, and serves to connect the two inferior 

 petrosal sinuses. It communicates with the anterior vertebral venous plexus. 



Emissary Veins (emissaria). The emissary veins pass through apertures in the 

 cranial wall and establish communication between the sinuses inside the skull and 

 the veins external to it. Some are always present, others only occasionally so. 

 The principal emissary veins are the following: (1) A mastoid emissary vein, 

 usually present, runs through the mastoid foramen and unites the transverse sinus 

 with the posterior auricular or with the occipital vein. (2) A parietal emissary 

 vein passes through the parietal foramen and connects the superior sagittal sinus 

 with the veins of the scalp. (3) A net-work of minute veins (rete canalis Jiypoglossi} 

 traverses the hypoglossal canal and joins the transverse sinus with the vertebral 

 vein and deep veins of the neck. (4) An inconstant condyloid emissary vein passes 

 through the condyloid canal and connects the transverse sinus with the deep veins 

 of the neck. (5) A net-work of veins (rete foraminis ovalis) unites the cavernous 

 sinus with the pterygoid plexus through the foramen ovale. (6) Two or three small 

 veins run through the foramen lacerum and connect the cavernous sinus w r ith the 

 pterygoid plexus. (7) The emissary vein of the foramen of Vesalius connects the 

 same parts. (8) An internal carotid plexus of veins traverses the carotid canal and 

 unites the cavernous sinus with the internal jugular vein. (9) A vein is trans- 

 mitted through the foramen cecum and connects the superior sagittal sinus with 

 the veins of the nasal cavity. 



THE VEINS OF THE UPPER EXTREMITY AND THORAX. 



The veins of the upper extremity are divided into two sets, superficial and deep; 

 the two sets anastomose frequently with each other. The superficial veins are 

 placed immediately beneath the integument between the two layers of superficial 

 fascia. The deep veins accompany the arteries, and constitute the vense comi- 

 tantes of those vessels. Both sets are provided with valves, which are more 

 numerous in the deep than in the superficial veins. 



The Superficial Veins of the Upper Extremity. 



The superficial veins of the upper extremity are the digital, metacarpal, cephalic, 

 basilic, median. 



'Digital Veins. The dorsal digital veins pass along the sides of the fingers and 

 are joined to one another by oblique communicating branches. Those from the 

 adjacent sides of the fingers unite to form three dorsal metacarpal veins (Fig. 

 573), which end in a dorsal venous net-work opposite the middle of the meta- 

 carpus. The radial part of the net-work is joined by the dorsal digital vein from the . 

 radial side of the index finger and by the dorsal digital veins of the thumb, and 

 is prolonged upward as the cephalic vein. The ulnar part of the net- work receives 



