THE CRANIAL NERVES. Tl 



nerves all disappear through the dura mater 

 closing in the skull cavity in front, and sep- 

 arating it from the orbital cavity. 



e. Carefully separate the soft parts beneath from 

 the bony roof of the temporal fossa and orbit, 

 and chip away the bone. Note the laxge fifth 

 nerve (trigeminal) arising from the anterior part 

 of the side of the medulla, and passing through 

 the dura mater ; also the Gasserian ganglion 

 (174), which may be exposed by removing the 

 membrane over it. 



/. Posterior to the fifth nerve, the seventh {facial) 

 and eighth {auditory) rise together from the side 

 of the medulla ; they soon diverge and pass 

 out by separate foramina, that of the seventh 

 being anterior to the cartilaginous inner side 

 of the labyrinth. 



g. The glosso-pharyngeal nerve {ninth cranial) arises 

 from the medulla, and leaves the skull by a 

 foramen in the opisthotic bone immediately 

 behind the cartilaginous portion of the inner 

 virall of the labyrinth. 



h. Immediately behind the glosso-pharyngeal a 

 number of nerve-roots arise from the side of 

 the medulla ; the anterior unite to form the 

 tenth nerve {pneumogastric) ; the posterior (re- 

 inforced by filaments from the anterior end of 

 the spinal cord) form the eleventh nerve, or 

 spinal accessory. The two leave the skull by a 

 large common foramen, between the exocci- 

 pital and opisthotic bones. 



/. The sixth and twelfth cranial nerves (abduceits 

 and hypoglossal respectively) have foramina of 



