180 ELEMENTABY BIOLOGY. [XIII. 



4. Paihetici 



arise from the floor of the mid-brain and pass out, on 

 the dorsal aspect of the brain, between the cerebellum 

 and the optic lobes. They are distributed to the 

 superior oblique muscles of the eye, 



5. Trigemini 



take their origin in the front part of the floor of the 

 hind-brain and, passing out at its sides, each dilates 

 into a yellow enlargement — the Gasserian ganglion — 

 which lies, in front of the auditory capsule, in the 

 foramen of the pro-otic bone by which the nerve, after 

 leaving the ganglion, passes out of the skull. 



This ganglion is connected with the trunk of the sixth 

 and seventh nerves and with the anterior end of the 

 sympathetic, and some of the branches which appear to be 

 given off from it really belong to the sixth and the seventh 

 nerves. Beyond the ganglion, the nerve divides into three 

 main branches, the orbito-nasal, the palatine and the maodllo- 

 mandibular. 



i. The orbito-nasal (usually termed the first division of 

 the fifth nerve) is distributed : 



a. To the external rectus. 



b. To the retractor of the bulb, 



(These branches {a and b) belong to the sixth nei-ve.) 



c. A branch which anastomoses with the fourth 



nerve. 



d. A branch to the Harderian gland. 



e. The principal trunk of the nerve passes through 

 the ant- orbital process of the skull into the nasal 



