46 A COURSE ON ZOOLOGY. 



its surface presents a large number of parallel striations, 

 and the white matter of the interior penetrates into the 



FIG. 25. 



OL 



UNDER SURFACE, OR BASE, OF BRAIN. FL. TL. and OL, frontal, temporal, 

 and occipital lobes of the cerebrum ; cb, cb, cerebellum, the medulla ob- 

 longata lying between its two lobes. Cranial Nerves. I, olfactory lobe (the 

 nerve of smell) ; 2, optic nerve (nerve of sight) ; 3, third or oculo-motor 

 nerve (motor nerve to most of the muscles of the eye) ; 4, fourth or troch- 

 lear nerve (motor nerve to the superior oblique muscle of the eye) ; 5, fifth, 

 trigeminus or trifacial, sensory and motor, the large root sensory to the 

 face and eyes, etc. ; the small root (motor) to muscles of mastication : 6, 

 sixth or abducens nerve, to external rectus muscle of eye, turns eyeball 

 outwards ; 7, seventh or facial, motor to muscles of expression ; 8, eighth or 

 auditory nerve, sensory for hearing (cochlea) and for equilibration (semi- 

 circular canals) ; 9, glosso-pharyngeal, sensory nerve of taste, and motor to 

 some of the muscles of deglutition ; 10, pneumogastric, sensory and motor 

 to larynx, lung, heart, and stomach ; 11, spinal accessory, motor to muscles 

 of heart (inhibitory) and sterno-mastoid and trapezius ; 12, hypoglossal, 

 motor to all the muscles of the tongue ; c\ t first cervical spinal nerve. 



gray matter of the exterior, producing an appearance 

 like the branches of a tree ; this may be easily seen 



