CRANIAL NERVES. 539 
2. The thalamencephalon or region of the optic thalami, with a 
thread-like pineal body above, infundibulum and pituitary 
body below, thinly roofed third ventricle within. 
3. The mesencephalon or mid-brain, with the optic lobes above, 
the crura cerebri below, the iter passing between. 
4. The cerebellum, with an anterior and a posterior lobe, both 
marked by ridges and grooves. 
5. The medulla oblongata, with thin vascular roof, with dorso- 
lateral extensions called “‘ restiform bodies.” 
The region beneath the thalamencephalon bears—(a) two ovoid inferior 
lobes ; (6) the infundibulum, which carries the pituitary body; and (c)a 
thin-walled three-lobed saccus vasculosus, situated between the pituitary 
body and the inferior lobes. 
Cranial nerves.!—Owing to the flat form of the skate 
and its frequently large size, the dissection of the cranial 
nerves is perhaps easier than in any other Vertebrate. 
Expecting practical verification, we shall describe their 
distribution in some detail, following in regard to certain 
points the investigations of Professor Cossar Ewart. 
I. The o/factory, rising from the olfactory lobes of the 
cerebral hemispheres, extend to the nostrils, and 
there expand in olfactory bulbs, which give off 
small nerves to the nostrils. 
II. The oftic, leaving the region of the optic thalami, 
cross in an optic chiasma, and extend to the 
retina of the eye. 
III. The oculomotor or ciliary, arising from the crura 
cerebri, near the mid-ventral line, supply four of 
the six muscles of the eye. There is a ciliary 
ganglion in connection with III and also with 
the ganglion of the ophthalmicus profundus. 
1] have to acknowledge indebtedness to Dr. Beard for his kindness 
in helping me to state the distribution of these nerves. 
fourth ventricle; OB., olfactory bulb ; OC., olfactory capsule ; 
SO.,.superior oblique muscle ; E., eye; SR., superior rectus; 
ER., external rectus ; SO.VII., superficial ophthalmic branch 
of VII. ; SO.V., superficial ophthalmic branch of V. ; OP., oph- 
thalmicus profundus; A.C., auditory capsule; B.Pl., brachial 
plexus ; R.F., recurrent facial ; C.T., chorda tympani; F.P., 
facial proper ; Hy., hyoidean ; Hyomn., hyomandibular ; E.M., 
external mandibular ; M.M., mandibular muscle ; Sp., spiracle ; 
P.sp., prespiracular ; Pl., palatine ; O.B., outer buccal ; Mn., 
mandibular; Mx., maxillary; 1.B., inner buccal; L., lateral 
branch of X.; Py., pyloric branch; C., cardiac branch. 
