THE CRANIAL NERVES. 133 



Hypoglossal.* In the relation of their functions they may be 

 arranged as nerves of special sense, nerves of common sensation, 

 motor nerves, and mixed nerves (i. e. both sensory and motor). 



C (I) olfactory, (II) optic, (VIII) audi- 

 Nerves of special sense, < toryf, and parts of (V) trigeminus 



(^ and (IX) glosso-pharyngeal. 



Nerves of common sen- ( The greater portion of the (V) trigem- 

 sation, { inus. 



{(Ill) motor oculi, (IV) patheticus, (V) 

 lesser division of the trigeminus, (VI) 

 abducens, (VII) facial, and (XII) hy- 

 poglossal, (XI) spinal accessory (?). 



Mixed nerves { ( IX ) g lo sso-pharyngeal and (X) pneu- 



( mogastric. 



What is the distribution of the motor oculi or third nerve ? 



It arises from a nucleus of gray matter just in front of the me- 

 dulla, beneath the iter e tertio ad quartum ventriculum, passing 

 out through the crus cerebri, and emerging from the skull in the 

 orbit. It gives off some fibres to the lenticular ganglion. It is 

 distributed to all the muscles of the eyeball, with the exception 

 of the superior oblique and the external rectus muscles. It also 

 supplies the levator palpebrae superioris muscle, and by its con- 

 nection with the lenticular ganglion controls the ciliary and pupil- 

 lary muscles. 



What is the function of the third nerve ? 



It is a purely motor nerve. Its function is best described, per- 

 haps, by showing the paralyses which follow its division : by par- 

 alysis of the elevator of the upper lid we have ptosis ; by the 

 paralysis of the muscles of the eyeball we have inability to move 

 the organ up or down or inward ; by the unopposed action of the 

 external rectus the eyeball becomes turned outward (external stra- 

 bismus) ; by the action upon the muscle of the iris the pupil 



* A convenient old medical-school mnemonic is useful in remembering the 

 names and order of these nerves viz. On Old Moriah's Pointed Top A 

 French And German Picked Some Hops, the initial letter of each word giv- 

 ing the key. It is given with an apology to many generations. 



f Of the nerves of special sense, (I) olfactory, (II) optic, and (VIII) audi- 

 tory will be explained later, and may be omitted from further consideration 

 for the present. 



