I.] THE FROG. I OS 



« a. The ist or olfactory nerve ; passing forwards in 

 front (cf. § 2. b). Remove the vomer of one 

 side and cut down to its level, following it out ; 

 it will be seen to ramify on the base of the ol- 

 factory sac. 



b. The 2nd or optic nerve ; arising from the optic 

 chiasma (§ 2. d) ; it runs forwards and upwards 

 to enter the eye-ball from below. 



c. The yd or oculo-motor nerve (described, in com- 

 mon with the 4th and 6th, in connection with 

 the eye-muscles. Sect. L. 3. p. n6). 



d. The $th or trigeminal nerve. Remove the eye- 

 ball on one side ; lying internally to it, deeply 

 seated and in close apposition with the cranial 

 wall, will be seen the ophthalmic or orbito-nasal 

 nerve (ist division of the 5th) ; trace it back, it 

 will be found to enter, immediately internal to 

 the front end of the auditory capsule — 



a. the Gasserian ganglion ; a comparatively large 

 oval pigmented body, seen to be in con- 

 nection with other nerves also. 



/J. The maxillo-mandibular nerve ; arising from 

 a and passing outwards immediately be- 

 hind the eye. It early subdivides into the 

 two following ; the mandibular nerve (3rd 

 division of the 5th) to the lower jaw and its 

 integument (follow it on that side in which 

 these still remain) ; the maxillary nerve (2nd 

 division of the 5th) seen, on removing the 

 hinder third of the upper jaw, to be somewhat 

 similarly distributed to the maxillary region. 



