CEREBRO-SPINAL NERVES. 371 



the first pair are the olfactive, which proceed from the bulbs 

 (1) of the olfactive peduncles, into the cavity of the nose. 

 Next to these are the optic nerves (2), which may be partly 

 traced to the optic ganglia, and 

 partly to the thalami optici. The 

 third (3), fourth (4), and sixth pairs 

 (6), are nerves of motion only, and 

 are distributed to the muscles of 

 the eye. The^A pair is for the 

 most part a nerve of sensation 

 only. Before leaving the skull, it 

 divides into three great branches ; 

 of which the first (5) passes into 

 the orbit (or cavity in which the 

 eye is lodged), endows the parts 

 contained in it with sensibility, 

 and then comes out beneath the 

 eyebrow, to be distributed to the 

 forehead and temples ; the second 

 (5') passes just beneath the orbit, 

 and makes its way out upon the 

 face, supplying the cheeks, nose, 

 upper lip, &c., which it endows 

 with sensibility; whilst the third 

 (5"), which (like the spinal nerves) 

 possesses a motor root also, supplies 

 the muscles of mastication with 

 the power of moving, and the 

 parts about the mouth with sensi- 

 bility. The seventh pair (7), or 

 facial, is the general motor nerve 

 of the face ; and this does not 

 endow the parts which it supplies 

 with the least sensibility. Beneath 

 the origin of this nerve is seen the 

 cut extremity of another trunk, 

 that of the auditory nerve (8), or 

 nerve of hearing. At 9 is seen the glosso-pharyngeal nerve, 

 which supplies the back of the mouth and pharynx, and is 

 concerned in the act of swallowing. Originating from the 

 upper part of the spinal cord (or medulla bloongata) very near 

 B B 2 



Fig. 197. BRAIN AND SPINAI 

 CORD OF MAN. 



