178 ZOOTOMY. 



a.c, anterior commissure: aq.s, aqueduct of Sylvius: ct>, cerebellum : 

 f.c, crura cerebri : c.h, cerebral hemispheres : ch.p, choroid plexus : c.s, 

 corpus striatum : /./, foramen of Monro : inf, infundibulum : m.o, 

 medulla oblongata : o.c, optic chiasma : o.l, optic lobes : olf, olfactory 

 lobes : o.t, optic tracts : o.v, aperture between aqueduct of Sylvius 

 and optic ventricle : p.c, posterior commissure : /, pineal body : pty, 

 pituitary body : z/.3, third ventricle : ^.4, fourth ventricle : I XII, 

 cerebral nerves. 



223. The cerebellum (cb), a small semicircular flap 

 covering the anterior part of the medulla oblongata on the 

 dorsal side. 



224. The fourth ventricle (7^.4), a cavity on the 

 dorsal surface of the medulla, roofed over in front by the 

 cerebellum, but for the rest of its extent covered only by 

 the pia mater, a delicate membrane investing the brain 

 and spinal cord. 



225. The optic lobes, or corpora bigemina (o.l), 

 two large rounded elevations on the dorsal surface of the 

 brain, immediately in front of the cerebellum : they consti- 

 tute the dorsal portion of the mid-brain, the ventral 

 region of which answers to the crura cerebri (c.c). 



226. The cerebral hemispheres (c.h), large, pyramidal 

 paired masses, immediately in front of the optic lobes, 

 against the anterior faces of which they abut closely : they 

 are in close contact with one another by their flat inner 

 faces, and are pointed in front. 



227. The olfactory lobes (olf) paired, club-shaped 

 bodies continued forwards from the anterior ends of the 

 cerebral hemispheres : from their dilated anterior ends are 

 given off the olfactory (first cerebral) nerves to the nasal 

 sacs. 



228. The pineal body (/), a small, rounded mass in 

 the middle line of the dorsal surface of the brain, at the 

 junction of the cerebral hemispheres and optic lobes. 



229. The pituitary body (pty) t a rounded mass situated 



