NERVOUS SYSTEM OF THE SKATE. 419 



The region beneath the thalamencephalon bears (a) two 

 ovoid inferior lobes, {b) the infundibulum which carries the 

 pituitary body, and (f) the thin-walled three-lobed saccus 

 vasculosus situated between the pituitary body and the 

 inferior lobes. 



The ten pairs of cranial nerves (see p. 381) are as 

 usual : — 



(i) The olfactory, issuing from the cerebral hemispheres, 

 expanding at the nostrils into bulbs shaped like 

 the heads of golf clubs. 



(2) The optic, fusing in a chiasma as they cross after 



leaving the optic thalami. 



(3) The oculomotor or ciliary, arising from the crura 



cerebri, supplying four of the muscles of the 

 eye. 



(4) The pathetic, arising from beneath the anterior 



sides of the cerebellum, supplying the superior 

 oblique muscle of the eye. 



(5) The trigeminal, arising from the medulla, and con- 



sisting {a) of a superficial ophthalmic or orbito- 

 nasal to the sensory tubes of the snout, ip) a 

 maxillary branch for the most part to anterior 

 sensory tubes, (c) of a third division, the man- 

 dibular to both upper and lower jaws. Another 

 nerve — the opthalmicus profundus — which sends 

 branches to the eye-ball, the snout, etc., is re- 

 ferred by some to the oculomotor, by others to 

 the trigeminal, and is regarded by others as an 

 independent nerve. 



(6) The slender abducens, arising along with the 5th 



and 7th, and supplying the external rectus muscle 

 of the eye. 



{7) The facial, arising along with the sth, including, 

 according to Prof Cossar Ewart, (a) super- 

 ficial ophthalmic, (p) buccal, (c) palatine, {d) 

 hyo-mandibular. The name ophthalmic is 

 applied, somewhat confusedly, to a branch of 

 the fifth, a branch of the seventh, and to the 

 ophthalmicus profundus. 



(8) The auditory, arising under the 5th and 7th, from 

 the medulla oblongata, innervating the ear. 



