THE 



OF THE DURA HATER. 



661 



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

 the glosso-pharvngeal, pneurnogastric. and spinal accessory nerves. These three 

 sets of structures are divided from each other by two processes of fibrous tissue. 

 The junction of the sinuses takes place superficial to the nerves, so that these latter 

 lie a little internal to the venous channels in the foramen (see Fig. 386). These 

 sinuses are semicylindrical in form. 



The Transverse Sinus, or basilar sinus, consists of several interlacing veins 

 between the layers of the dura mater over the basilar process of the occipital bone, 

 which serve to connect the two inferior petrosal sinuses. With them the anterior 

 spinal veins communicate. 



Emissary Veins. The emissary veins are vessels which pass through apertures 



Falx cerebri 



Optic nerve 

 Int. carotid artery 



Motor oculi nerre 



Inferior 

 petrosal fi 



Dorsum sellse 



9th. 10th. and llt'.t 

 cranial nerves 



Lateral finus 

 Fin. 3S6. Relation of nerves to sinuses in jugular foramen. (Henle.) 



in the cranial wall and establish communications between the sinuses inside the 

 skull and the veins external to it. Some of these are always present, others only 

 occasionally so. They vary much in size in different individuals. The principal 

 emissary veins are the following: 1. A. vein, almost always present, which passes 

 through the mastoid foramen and connects the lateral sinus with the posterior 

 auricular or with an occipital vein. 2. A vein which passes through the parietal 

 foramen and connects the superior longitudinal sinus with the veins of the scalp. 



3. A plexus of minute veins which pass through the anterior condyloid foramen 

 and connect the occipital sinus with the vertebral vein and deep veins of the neck. 



4. An inconstant vein which passes through the posterior condyloid foramen and 

 connects the lateral sinus with the deep veins of the neck. 5. One or two veins 

 of considerable size which pass through the foramen ovale and connect the cav- 

 ernous sinus with the pterygoid and pharvngeal plexuses. 6. Two or three small 

 veins which pass through fhe foramen lacerum medium and connect the cavernous 

 sinus with the pterygoid and pharyngeal plexuses. 7. There is sometimes a small 



