i88 ELEMENTARY BIOLOGY. [CHAP. 



except the external rectus, the superior oblique and 

 the retractor bulbi. 



4. Pathetid 



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

 on the dorsal aspect of the brain, between the cere- 

 bellum 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 sym- 

 pathetic, 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 maxillo- 

 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 nerve.) 



c. A branch which anastomoses with the fourth 

 nerve. 



d. A branch to the Harderian gland. 



c. The principal trunk of the nerve passes through 



