28 ELEMENTARY BIOLOGY. [CHAP. 



4. Pathctici 



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 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 (some of the branches which appear to be given 

 off from it really belong to the sixth and the seventh nerves. 

 Bee infra). Beyond the ganglion, the nerve divides into 

 two main branches, the orbito-nasal, and the maxillo-mandi- 

 bular. 



i. The orhito nasal (usually termed the first division of 

 the fifth nerve); passing through the antorbital pro- 

 cess of the skull, it is finally distributed to the nasal 

 mucous membrane and to the integument of the nose. 

 It anastomoses with the fourth nerve, and sends a 

 branch to the Harderian gland. 



ii. The maxillo-mandibular ; forks over the mouth-cavity 

 into two trunks, usually termed the second and third 

 divisions of the fifth nerve. 



a. Preoral or Maxillary^ passes outside the eye and 

 is distributed to the integument of the upper jaw. 



