I076 A MANUAL OF ANATOMY 



posterior clinoid process, where it occupies a notch on the bone. 

 It lies a little to the inner side of the fifth nerve. 



The seventh or facial nerve, the eighth or auditory nerve, and the 

 pars intermedia of Wrisberg, accompanied by the internal auditory 

 artery, enter the meatus auditorius internus. 



The ninth or glosso-pharyngeal nerve, the tenth or pneumogastric 

 nerve, and the eleventh or spinal accessory nerve pass through the 

 middle compartment of the jugular foramen. This foramen is 

 divided into three compartments, namely, antero-internal, middle, 

 and postero -external. The antero-internal compartment gives 

 passage to the inferior petrosal sinus. The middle compartment 

 transmits the glosso-pharyngeal, pneumogastric, and spinal acces- 

 sory nerves, in this order from before backwards. The glosso- 

 pharyngeal nerve pierces the dura mater separately, and receives 

 special sheaths from the dura mater and arachnoid membrane. 

 The pneumogastric and spinal accessory nerves pass through the 

 same aperture in the dura mater, and receive common sheaths from 

 the dura and arachnoid membrane. The postero -external com- 

 partment transmits the lateral sinus, which terminates in the internal 

 jugular vein. 



The twelfth or hypoglossal nerve pierces the dura mater in two 

 bundles, which pass through separate apertures. As these bundles 

 pass through the anterior condylar foramen they unite to form one 

 nerve. 



Structures passing through the Foramen Magnum. — (i) The 

 medulla oblongata, with its membranes, passes out and becomes 

 the spinal cord. (2) The spinal portion of the spinal accessory 

 nerve, of either side, having ascended from the interval between the 

 posterior roots of the cervical spinal nerves and the ligamentum 

 denticulatum, enters the cranial cavity. It then turns outwards 

 to the middle compartment of the jugular foramen, where it meets • 

 the bulbar portion of the nerve, with which it Ijecomes closely 

 connected as it passes through the foramen. (3) The vertebral 

 artery of each side enters the cranial cavity, after having left the 

 vertebrarterial groove on the upper aspect of the posterior arch of 

 the atlas. (4) The two anterior spinal branches of the vertebral 

 arteries descend on the front of the medulla oblongata, and, inclining 

 inwards towards each other, they unite in passing through the 

 foramen magnum to form the anterior spinal artery. (5) The two 

 posterior spinal branches of the vertebral arteries pass outwards 

 through the foramen magnum. (6) Parts of the cerebellar amygdahc. 



Gasserian Ganglion. — ^The Gasserian ganglion occupies the Gas- 

 serian depression on the superior surface of the petrous part of the 

 temporal bone near the apex, where it lies in a recess of the dura 

 mater, called Meckel's cave. It is somewhat semilunar, being con- 

 vex in front and conca,ve behind, and measures fully | inch from 

 before backwards. It is associated with the sensory root of the 

 fifth nerve, which, before entering the posterior concave aspect 

 of the ganglion, becomes expanded, its fasciculi at the same 



