HEAD AND NECK 



traverse the foramen in close contact with each other. 

 Reaching the exterior of the skull, the three become 

 associated with the hypoglossal nerve; and the four nerves 

 lie for a short distance in the interval between the internal 

 jugular vein and the internal carotid artery, but soon they 

 choose different routes. The accessory inclines posteriorly, 

 superficial or deep to the internal jugular vein ; the glosso- 

 pharyngeal runs anteriorly, superficial to the internal carotid, 



Oculo-motor nerve 



Trochlear nerve 



Sensory root of the trigeminal nerve 

 Motor root of the trigeminal 

 erve 



Abducent nerve 



Motor root of facial 

 \ nerve 



..Cut edge of the 

 tentorium 



-Sensory root of 

 facial nerve 

 -Acustic nerve 

 Right transverse 

 "sinus 



losso-pharyngeal 

 nerve 

 Vagus nerve 



uccessory nerve 



rtebral artery 

 Hypoglossal nerve 

 irst spinal nerve 

 Accessory nerve 



FIG. 125. 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 under cover of the posterior belly of the digastric ; at 

 a lower level the hypoglossal turns anteriorly across the 

 external and internal carotid arteries ; and the vagus proceeds 

 vertically downwards, first between the internal jugular vein 

 and the internal carotid, and then between the vein and the 

 common carotid (Fig. 100). 



In an ordinary dissection it is impossible to follow out many of the 

 minute twigs which take origin from these nerves in the region of the 

 basis cranii. To do so it is necessary to possess a perfectly fresh part 

 which has been specially prepared by having the soft parts toughened with 

 spirit and the bone softened by immersion in a weak solution of acid. 



