112 



HEAD AND NECK 



vagus nerves the smaller trunk of the glossopharyngeal nerve 

 pierces the dura. Above the glossopharyngeal nerve the acoustic 

 nerve and the motor and sensory roots of the facial nerve pass 

 into the internal acoustic meatus, accompanied by the small 

 auditory branch of the basilar artery and the auditory vein. 

 The two roots of the facial nerve lie in a groove on the upper 

 and anterior aspect of the acoustic nerve, the small sensory root 

 (O.T. pars intermedia) being situated between the motor root 

 and the acoustic nerve. The small motor and the large sensory 

 root of the trigeminal nerve pass through an opening in the 

 dura which lies above and medial to the internal acoustic meatus ; 



Trochlear nerve 



Oculo-motor nerve /- Sensory root of the trigeminal nerve 



Motor root of the trigeminal 



Abducens nerve 



Motor root of facial 

 nerve 



Cut edge of the 

 :entorium 



Sensory root of 

 facial nerve 

 Acoustic nerve 

 Right transverse 

 sinus 



Glosso-pharyngeal 

 nerve 

 Vagus nerve 



Accessory nerve 



Vertebral artery 

 Hypoglossal nerve 

 First spinal nerve 

 Accessory nerve 



FIG. 37. Section through the Head a little to the right of the median 

 plane. It shows the posterior cranial fossa and the upper part of the 

 vertebral canal after the removal of the brain and the medulla spinalis. 



and the abducens nerve pierces the dura mater below and to the 

 medial side of the opening for the trigeminal nerve, opposite 

 the side of the base of the dorsum sellae. The small trochlear 

 nerve pierces the inferior surface of the free border of the ten- 

 torium at the point where it is crossing the attached border. 



After the dissectors have familiarised themselves with the 

 positions of the cerebral nerves as they pierce the dura mater, 

 they should examine the falx cerebelli and complete the 

 display of the cranial blood sinuses. 



Falx Cerebelli. The falx cerebelli is a small sagittal fold 



