THE BEAIN 357 



Identify, and clean the nerve-roots on one side of the brain, 

 in the order gi/ven below, taking great ca/re not to drag them 

 away from the brain. 



1. The olfactory nerve arises, by many roots, from the 



ventral surface of the anterior end of the olfactory 

 lobe. These roots are almost necessarily removed 

 in taking out the brain. 



2. The optic nerve is a stout nerve, running forwards from 



the anterior border of the optic chiasma, and then 

 curving outwards. 

 8. The oculo-motor nerve is small, and arises from the inner 

 border of the crus cerebri, close to the middle line, 

 and immediately behind the corpus mammiUare. 



4. The pathetic nerve is very small. It arises from the 



dorsal surface of the valve of Vieussens, close to the 

 middle line, and just behind the optic lobes. It then 

 runs round the side of the brain to the ventral sur- 

 face, lying between the cerebellum and optic lobe. 



Find the nerve on the ventral surface, and follow it round 

 the side of the brain to its origin. 



5. The trigeminal nerve is very large, and arises by two 



closely apposed roots from the side of the hinder 

 border of the pons Varolii. Of the two roots the 

 inner and smaller one is motor, the larger outer one 

 sensory in function. 



6. The abducent nerve is very slender, and arises from the 



ventral surface of the medulla, close to the middle 

 line, and immediately behind the pons Varolii. 



7. The facial nerve arises from the outer side of the ante- 



rior end of the corpus trapezoideum, immediately 

 behind the trigeminal nerve. 



8. The auditory nerve is large, and arises from the side 



of the medulla, immediately behind and to the outer 

 side of the facial nerve. 

 9 and 10. The glosso-pharyngeal and pneumogastric nerves 

 arise close together, by many slender rootlets, from 



