I.] THE FROG. 105 



a. The 1st or olfactory nerve ; passing forwards in 

 front (cf. § 2, h). 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. 



h. 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 2)^d or oculo-motor nerve (described, in com- 

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

 the eye-muscles. Sect. L. 3. p. 116). 



d. The ^tJi 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. 



/?. The inaxillo-mandibular nerve ; arising from 

 a and passing outwards immediately be- 

 hind the eye. It early subdivides into the 

 two following ; the mandil^ular nerve (3rd 

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

 integument (follow it on that side in which 

 these still remain) ; the maxillary nen'e (2nd 

 division of the 5th) seen, on removing the 

 hinder third of the upper jaw, to be somewhat 

 similarly distributed to the maxillary region. 



